WATER POLLUTION CONTROL RESEARCH SERIES • 13O3OELY5/7I-
REC-R2-7I-3
DWR NO. \~74r-
BIO-ENGINEERING ASPECTS OF AGRICULTURAL DRAINAGE
SAN JOAQUIN VALLEY, CALI FORNI A
NUTRIENTS FROM TILE DRAINAGE
SYSTEMS
MAY I9TI
NVIRONMENTAL PROTECTION AGENCY0RESEARCH AND MONITORING
CALIFORNIA DEPARTMENT OF WATER RESOURCES
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ASPECTS OF AGRICULTUBAL DRAINAGE
SAN JOAQUIM VAUiEY, CALIFORNIA
The Bio-Engineering Aspects of Agricultural Drainage
reports describe the results of a unique interageney study
of the occurrence of nitrogen and nitrogen removal treat-
ment of subsurface agricultural wastewaters of the San
Joaquin Valley, California,
The three principal agencies involved in the study are
the Water Quality Office of the Environmental Protection
Agency, the United States Bureau of Reclamation, and the
California Department of Water Resources.
Inquiries pertaining to the Bio-Engineering Aspects of
Agricultural Drainage reports should be directed to the
author agency, but may be directed to any one of the three
principal agencies.
THE REPORTS
It is planned that a series of twelve reports will be
issued describing the results of the interagency study.
There will be a summary report covering all phases of
the study.
A group of four reports will be prepared on the phase of
the study related to predictions of subsurface agricul-
tural wastewater quality — one report by each of the
three agencies, and a summary of the three reports.
Another group of four reports will be prepared on the
treatment methods studied and on the biostinmlatory
testing of the treatment plant effluent. There will be
three basic reports and a summary of the three reports.
This report, "NUTRIENTS FROM TILE DRAIN SYSTEMS", is one
of the three basic reports of this group.
The other three planned reports wiH cover (1) techniques
to reduce nitrogen during transport or storage, (2) possi-
bilities for reducing nitrogen on the farm, and
(3) desalination of subsurface agricultural wastewaters.
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BIO-ENGINEERING ASPECTS OF AGRICULTURAL DRAINAGE
SAN JOAQUIN VALLEY, CALIFORNIA
NUTRIENTS FROM TILE
DRAINAGE SYSTEMS
Prepared by the
California Department of Water Resources
William R. Gianelli, Director
The agricultural drainage study was conducted under the direction of:
Robert J. Paffordjr., Regional Director, Region 2
UNITED STATES BUREAU OF RECLAMATION
2800 Cottage Way, Sacramento, California 95825
Paul DeFalco, Jr., Regional Director, Pacific Southwest Region
WATER QUALITY OFFICE, ENVIRONMENTAL PROTECTION AGENCY
760 Market Street, San Francisco, California 94102
John R. Teerink, Deputy Director
CALIFORNIA DEPARTMENT OF WATER RESOURCES
1416 Ninth Street, Sacramento, California 95814
May 1971
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REVIEW NOTICE
This report has been reviewed by
the Water Quality Office, Environ-
mental Protection Agency and the
U. S. Bureau of Reclamation, and
has been approved for publication.
Approval does not signify that the
contents necessarily reflect the
views and policies of the Water
Quality Office, Environmental
Protection Agency, or the U. S.
Bureau of Reclamation.
The mention of trade names or
commercial products does not
constitute endorsement or recom-
mendation for use by either of the
two federal agencies or the Cali-
fornia Department of Water Resources.
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ABSTRACT
Tile drainage systems of the San Joaquin Valley were
monitored for nutrients (nitrogen and phosphorus). The
objectives were to determine: (l) the average nutrient
concentrations in tile drainage, (2) the magnitudes of
annual, areal and seasonal variability of nutrients and
discharges, (3) if a possible correlation exists between
nutrients and agricultural practices, and (4) if existing
soil conditions Influence nutrient concentrations and flows.
From this information it will be possible to determine the
algal growth potential (AGP) of the waste, and the degree
of treatment required for removal of AGP.
Average discharges, nutrient concentrations and total
dissolved solids were calculated for different years, months,
physiographic positions, soil series, and valleywide areas
of interest. Average nutrient concentrations in the compos-
ited drainage from the Valley were found to be 19-3 mg/1 for
nitrate-nitrogen, 0.09 rag/1 for phosphate-phosphorus, and
3,625 mgA for total dissolved solids; average discharge was
1.4 ac-ft/ac. Nutrient levels in the composited drainage
did not change appreciably from year to year. Variability
of nutrients was observed for different seasons; a twofold
decrease in nutrients was attributed to dilution by irriga-
tion and denitrification. Nitrogen was three times more
concentrated in drainage from one out of four major tiled
areas investigated. The high nitrogen levels were attrib-
uted more to indigenous concentrations in certain alluvial
fan soils and their parent materials than fertilization.
Low nitrogen levels found in drainage from basin soils were
believed caused by denitrification. Phosphorus was seven
times higher in the drainage from the southernmost area than
the other areas investigated. These extraordinarily high
levels (0.69 mg/l) were attributed to indigenous concentra-
tions in certain soils made available by anaerobic soil
conditions. High discharge in the northernmost area (2.3
ac-ft/ac) was believed to be caused by rapid lateral
hydraulic conductivity and surrounding irrigation influence.
This report was prepared by the California Department of
Water Resources in conjunction with other agricultural waste-
water studies which were conducted by the United States
Bureau of Reclamation and the Water Quality Office of the
Environmental Protection Agency.
Key words: agricultural waste, tile drainage, nutrients,
composited drainage, nutrient variability,
Indigenous concentrations.
iii
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BACKGROUND
This report is one of a series which presents the findings
of intensive interagency investigations of practical means
to control the nitrate concentration in subsurface agricul-
tural wastewater prior to its discharge into other water.
The primary participants in the program are the Water
Quality Office of the Environmental Protection Agency, the
United States Bureau of Reclamation, and the California
Department of Water Resources, but several other agencies
also are cooperating in the program. These three agencies
initiated the program because they are responsible for
providing a system for disposing of subsurface agricultural
wastewater from the San Joaquin Valley of California and
protecting water quality in California's water bodies.
Other agencies cooperated in the program by providing
particular knowledge pertaining to specific parts of the
overall task.
The need to ultimately provide subsurface drainage for large
areas of agricultural land in the western and southern San
Joaquin Valley has been recognized for some time. In 195^>
the Bureau of Reclamation included a drain in its feasibility
report of the San Luis Unit. In 1957, the California Depart-
ment of Water Resources initiated an investigation to assess
the extent of salinity and high ground water problems and to
develop plans for drainage and export facilities. The Burns-
Porter Act, in I960, authorized San Joaquin Valley drainage
facilities as a part of the state water facilities.
The authorizing legislation for the San Luis Unit of the
Bureau of Reclamation's Central Valley Project, Public Law
86-488, passed in June I960, included drainage facilities
to serve project lands. This Act required that the Secretary
of Interior either provide for constructing the San Luis
Drain to the Delta or receive satisfactory assurance that
the State of California would provide a master drain for
the San Joaquin Valley that would adequately serve the San
Luis Unit.
Investigations by the Bureau of Reclamation and the Depart-
ment of Water Resources revealed that serious drainage
problems already exist and that areas requiring subsurface
drainage would probably exceed one million acres by the year
2020. Disposal of the drainage into the Sacramento-San
Joaquin Delta near Antioch, California, was found to be the
least costly alternative plan.
v
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Preliminary data indicated the drainage water would be
relatively high in nitrogen. The then Federal Water Quality
Administration conducted a study to determine the effect of
discharging such drainage water on the quality of water in
the San Francisco Bay and Delta. Upon completion of this
study in 196?, the Administration's report concluded that
the nitrogen content of untreated drainage waters could have
significant adverse effects upon the fish and recreation
values of the receiving waters. The report recommended a
three-year research program to establish the economic feasi-
bility of nitrate-nitrogen removal.
As a consequence, the three agencies formed the Interagency
Agricultural Wastewater Study Group and developed a three-
year cooperative research program which assigned specific
areas of responsibility to each of the agencies. The scope
of the investigation included an inventory of nitrogen
conditions in the potential drainage areas, possible control
of nitrates at the source, prediction of drainage quality,
changes in nitrogen in transit, and methods of nitrogen
removal from drain waters including biological-chemical
processes and desalination.
vl
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TABLE OF CONTENTS
Page
ABSTRACT iii
BACKGROUND v
SECTION I. SUMMARY AND CONCLUSIONS 1
Summary 1
Average Nitrogen (nitrate-nitrogen)
Concentrations 1
Variations of Nitrogen Concentrations 1
Levels and Sources 3
Phosphorus (phosphate-phosphorus) 5
Total Dissolved Solids 6
Discharges 7
Conclusions 7
SECTION II. INTRODUCTION 9
Area of Investigation 9
Isolated Tile Systems 10
Objectives 10
SECTION III. TILE DRAINAGE IN THE
SAN JOAQUIN VALLEY 13
Historic Background 13
Tile Drain Design 13
Materials, Construction, and Installation 14
Conduit 15
Filter Materials 15
Installation 16
Sumps and Outlets 17
vii
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TABLE OP CONTENTS (Continued)
Effective and Critical Placement of Tile Drain .... 19
Physiographic Positions 19
Recent Alluvial Fan 19
Older Alluvial Fan 20
Basin Rim 20
Basin 20
Tiled Acreages within Physiographic Positions ... 21
Soils and Soil Characteristics 21
Morphology and Genesis 21
Description of Soils 22
Soils on Recent Alluvial Fans 24
Soils of Older Alluvial Fans 24
Soils of the Basin Rim Position 25
Soils of the Basin Position 25
Climate 26
Temperature 26
Precipitation 27
Agriculture and Agricultural Practices 27
Crops 28
Current Irrigation 29
Sources 29
Types of Irrigation 29
SECTION IV. METHODS AND MATERIALS 31
Monitoring Tile Drainage Systems 31
Historical Monitoring 31
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TABLE OP CONTENTS (Continued)
Page
Selection of Tile Drainage Systems
for Monitoring 32
Acreages Monitored 33
Tile Monitoring Techniques 34
Plow Measurement 34
Nutrient Sampling 35
Collection of Mineral Samples 36
Collection of Dissolved Oxygen Samples 36
Laboratory Techniques 36
Nitrogen Determinations 37
Phosphorous Determinations 38
Electrical Conductivity 38
Soil Extracts 38
Collection of Agricultural Data 38
Crops 38
Irrigation 38
Irrigation Runoff 39
Fertilization 39
Historical Use of Fertilizers 39
Types and Methods of Use 40
Volatilization 40
Data Sources 41
Investigations of Native Nitrogen 41
Soil Profile Nitrogen Sampling 41
Parent Material Nitrogen Sampling 41
SECTION V. RESULTS AND DISCUSSION 43
Average Nutrient Concentrations 43
Average Discharge 43
Variability of Nutrient Concentrations and
Tile Discharge with Time 44
Long-term Nitrogen Variability ... 44
Composited Drainage 44
Individual Systems 45
ix
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TABLE OP CONTENTS (Continued)
Page
Short-term Nitrogen Variability 4?
Hourly 48
Daily 48
Monthly Variations In Individual Systems .... 50
Monthly Variations in Composited Drainage .... 50
Areal Variability 51
Individual Systems 51
Composited Drainage 52
Tile Drain Discharge 52
Nitrogen 52
Phosphorus 53
Total Dissolved Solids 53
Variability Due to Agricultural Practices 53
Influence of Crops on Tile Discharge 53
Influence of Crops on Nitrogen Concentrations ... 54
Irrigation Influence on Discharges 55
Irrigation Influence on Nitrogen Concentrations . . 55
Individual Systems 55
Denitrification 56
Dilution 57
Nitrogen in Irrigation Water 58
Fertilization 58
Leaching 58
Applied Nitrogen Versus Discharged Nitrogen ... 59
Phosphorous Fertilization 60
Variability Due to Physiography 6l
Discharge 6l
Nutrients and Total Dissolved Solids 6l
Variability Due to Soils 62
Discharge 62
Nutrients 64
x
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FIGURES
Figure
Number
TABLE OF CONTENTS (Continued)
Page
Total Dissolved Solids 65
Drainage Site Classes 66
Residual Nitrogen in West Side Soils 69
Background 69
Ranges and Magnitudes 71
Variability of Nitrogen from Different Sites ... 72
Virgin Sites 73
Irrigated Sites 73
Alluvial Fan and Interfan Sites 73
Different Geographical Sites 75
Nitrogen in Soils and Tile Drainage 75
Saturation Extracts and Field Extracts 75
Soil-Moisture Relationships 76
Field Comparisons 77
Future Tile Drainage 79
San Luis Unit Service Area 80
Residual Nitrogen in Parent Materials of
West Side Soils 83
Genesis and Morphology 83
Nitrogen Concentrations in Parent Materials ... 83
SECTION VI. REFERENCES 85
SECTION VII. PUBLICATIONS 89
1 Major Tiled Areas of the
San Joaquin Valley ............. 11
2 Interceptor System
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FIGURES (Continued)
Figure
Number Page
3 Total Relief System 14
4 Concrete Pipeline Installation 17
5 Typical Tile Drainage System -
West Side of the San Joaquln Valley 18
6 Concrete Sump 18
7 Monthly Average Temperature at Los Banos . . 27
8 "Float Method" Flow Measurement 35
9 Sampling Methods — Nutrients 36
10 Variability of Flow, Nutrients, and
Total Dissolved Solids from a
Flooded Tile Drainage System 51
11 Variability of Flow, Nutrients, and
Total Dissolved Solids from a Periodically
Irrigated Tile Drainage System 51
12 Seasonal Variations of Discharge,
Nutrient Concentrations, and
Total Dissolved Solids 52
13 Seasonal Variation of Nitrogen
Concentrations in Different
Groupings of Soils 65
14 Seasonal Distribution of Nitrogen Yield
in Different Groupings of Soils 65
15 Drainage Site Classes -- Gustlne
to Mendota Area 66
16 Nitrate Concentrations within Deep Profiles
of East and West Side Soils 70
17 Quantities of Nitrate in Deep Profiles
of East and West Side Soils 70
18 Quantities of Nitrate Above the Water
Table in Deep Profiles of East
and West Side Soils 70
xii
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TABLES
Table
Number Page
1 Tile Acreages within Major Physiographic
Positions of the San Joaquln Valley
Floor, 1968 21
2 Acreages and Number of Tile Systems
within Different Soil Series and
Physiographic Positions, 1968 . 23
3 Average Annual Temperature at Selected
Weather Stations Along the West Side .... 26
4 Annual Precipitation at Selected
Weather Stations Along the West Side .... 28
5 Acreage Tiled and Acreage Sampled for
Nutrients in Major Tiled Areas 33
6 Tile Drainage Systems and Acres Sampled
by Soil Series and Physiographic Positions
within the Major Tiled Areas, 1968 34
7 Average Discharge, Nutrient Concentrations,
and Total Dissolved Solids from San Joaquln
Valley Tile Drainage Systems 44
8 Nutrients, Total Dissolved Solids and
Plows from Individual Tile Drains by Year . . 46
9 Hourly Variation of Plows, Nutrients and
Electrical Conductivity in Drainage
from Pour Tile Drainage Systems 48
10 Hourly Vs. Weekly Nitrogen Concentrations . . 49
11 Average Discharge, Nutrient Concentrations,
and Total Dissolved Solids by Major
Tiled Areas, 1967 and 1968 53
12 Comparison of Tile Drain Discharge by
Various Crops 54
13 Tile Drain Discharge Vs. Irrigation
Intensity within Major Tiled Areas, 1967 • • 56
14 Dissolved Oxygen Concentrations in
Tile Drainage from Various Crops ...... 57
xiii
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TABLES (Continued)
Table
Number
15 Applied Nitrogen Vs. Discharged
Nitrogen by Major Tiled Areas
16 Tile Drain Discharge, Nutrient
Concentrations, and Total Dissolved
Solids Summarized by Physiographic
Positions, 1967-68 ............ 62
1? Average Tile Drain Discharge, Nutrient
Concentrations, and Total Dissolved
Solids from Different Soil Series and
Physiographic Positions .......... 63
18 Meanings of Map Symbols Used for
Designating Drainage Site Classes ..... 67
19 Average Tile Drain Discharge, Nutrient
Concentrations and Total Dissolved
Solids According to Drainage Site
Classes, 1968 ............... 68
20 Extract Analysis of a Virgin Alluvial
Soil on the West Side of the
San Joaquin Valley ............ 71
21 Average Nitrogen Concentrations in
Virgin, Irrigated, and Dry Farmed Soil
Profiles Along the West Side of the
San Joaquin Valley ............ 72
22 Nitrogen In Virgin and Irrigated
Soil Profiles ............... 7^
23 Residual Nitrogen in Virgin Soil Profiles
of Alluvial Pan and Interfan Areas .... 7^
24 Nitrogen Concentrations in Saturation
Extracts and Drainage from Three Tiled
Fields of the Panoche Series, 1966 .... 77
25 Nitrogen Concentrations in Field
Moisture and Drainage from Four Tiled
Fields, 1967 ................ 78
26 Nitrogen Concentrations in Saturation
Extracts and Tile Drainage from
Irrigated Sites .............. 79
XIV
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TABLES (Continued)
Table
Number Page
27 Nitrate-Nitrogen Concentrations in
Irrigated West Side Soils
Investigated by USER 8l
28 Nitrate-Nitrogen Concentrations for
Different Soil Series Investigated
by USER 82
29 Summary of Nitrate-Nitrogen
Concentrations Found in Parent Materials
of West Side Alluvial Pan Soils 84
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SECTION I
SUMMARY AND CONCLUSIONS
Summary
Tile drainage systems in the San Joaquin Valley were inten-
sively monitored from 1966 through 1968. This report empha-
sizes nutrient data collected during that period. Nutrient
and soils data are also presented from investigations
conducted prior to 1966, from other investigations during
the 1966 through 1968 period, and from a continuing monitor-
ing program which was initiated in 1969.
Average Nitrogen (nitrate-nitrogen) Concentrations
The nitrate ion (NO^) is the dominant nitrogen constituent
found in San Joaquin Valley tile drainage. The combined
amounts of ammonium (Nlty), nitrite (N02), and organic
nitrogen rarely exceed 1.0 milligram per liter (mg/l) in the
drainage regardless of the total levels found. All discus-
sions of nitrogen that follow in this report will be limited
to nitrate-nitrogen.
Nitrogen averaged 19.3 mg/l in the combined drainage from
tile systems monitored on a regular basis from 1962 through
1969. During 1968, forty-two tile systems were monitored
weekly for a full year in all of the major tiled areas.
During the same period a number of "isolated" and "satellite"
tile systems were also sampled monthly during most of the
year. The composite drainage from all of these systems
averaged 20 mg/l.
Variations of Nitrogen Concentrations
The average nitrogen concentration remained relatively
constant from year to year during the more intensive investi-
gations. During 196? and 1968, the annual averages were
18.6 mg/l and 19.9 mg/l, respectively. The annual average
for 1969 (19.^ mg/l) was only slightly less than that of 1968,
The greatest long-term change in average nitrogen levels
appeared to occur between 1962 and 1960 when the concentra-
tion decreased from 25.1 mg/l to 18,6 mg/l, respectively.
This change occurred primarily because a larger number of low
nitrogen level tile systems were sampled in 1966 that were
not included in the earlier investigations.
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Long-term variability of nitrogen was., however, apparent In
the drainage from individual tile systems. Though the
overall percentage of change was small, the absolute changes
were on the order of 6 to 8 mg/1 over a decade. This degree
of variability is due primarily to changes in agricultural
management which includes the type of crop grown and the
irrigation frequency and duration.
Nitrogen accumulation in the subsoil due to fertilization or
leaching of nitrogen from the soil due to irrigation was not
apparent in the drainage observed from the individual
systems studied over several years. High concentrations of
nitrogen are still found in the drainage from fields tiled
since 1950 and irrigated for forty or more years in the San
Joaquin Valley.
Nitrogen also varies on a short-term basis in drainage from
individual systems. Hourly, daily, and weekly variability
was studied for several drainage systems. During a 24-hour
sampling period, nitrogen ranged from 4 mg/1 to 12 mg/1 in a
particular drain that had a fixed discharge. The standard
deviation was 1.8 mg/1. Another system, considered rather
typical of many along the west side of the Valley, had hourly
concentrations that ranged from 92 mg/1 to 182 mg/1 and a
standard deviation of 19.8 mg/1. For the most part these
hourly variations were comparable to those observed from
week to week during the tile monitoring investigations.
These short-term'changes of nitrogen in drainage can be
attributed to dynamic moisture conditions — caused by
varying irrigation patterns and soil texture combinations.
Nitrogen varies monthly in drainage composited from the San
Joaquin Valley tile systems. Monthly changes were gradual
but rather consistent from year to year. Two-fold seasonal
variations were observed; nitrogen concentrations in the
composited drainage were about 3^ mg/1 in March and 14 mg/1
in August.
Nitrogen concentrations vary in drainage from certain
geographical areas in the San Joaquin Valley. Drainage was
composited separately for the four heavily tiled areas in
the Valley. The systems sampled represent about one-third
of present total tiled acreage. These major tiled areas are:
two northern areas (Byron to Westley and Westley to Gustine),
the central area (Gustine to Mendota) and the southern area
(Tulare lakebed). Nitrogen concentrations averaged 33 mg/1
in drainage from the central area, which was more than three
times higher than the drainage from either of the two
northern areas or the southern area. At first these varia-
tions were thought to be due to differences in fertilizer
application. Immediate or prolonged fertilization had no
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observable effect upon nitrogen concentrations in the tile
drainage. Agricultural records collected by the Department
show that many tile systems were fertilized heavily over
the years but discharged effluent relatively low in nitrogen,
A study of agricultural practices revealed that irrigation
was the only agricultural practice that greatly influenced
changes in nitrogen concentrations. Immediate decreases in
nitrogen levels were observed in drainage from many tiled
rice fields during flooding. Drainage from one large tile
system decreased from 63 rag/1 in the winter to 7 mg/1 in the
summer. Nitrogen concentrations fluctuated in drainage from
other tiled crops during irrigation but generally decreased
during the summer months. Denitrification and dilution are
highly suspected as the reasons for summer decreases in
nitrogen concentrations.
Levels and Sources
The level of nitrogen concentrations was found to be most
related to location and type of soil (physiographic position
and soil series). Drainage from tile systems occupying
recent or older alluvial fans generally was higher in
nitrogen than drainage from tile systems located in basin or
basin rim physiographic positions. Nitrogen concentrations,
however, were much higher in drainage from tile systems
located in alluvial fans of the central area than drainage
from systems located in similar fans of the two northern
areas. These differences led to a close look at the
individual soil series as a source of nitrogen in the
drainage.
The highest concentrations of nitrogen (about 45 mg/1)
occurred in drainage from the Panoche family group (Panhlll,
Panoche, and Lost Hills soil series) of the central area.
Nitrogen levels were roughly 10.0 mg/1 in drainage from the
Sorrento family of soils (Sorrento, Rincon, and Ambrose soil
series), and other nonrelated basin and basin rim soils.
Soil investigations were conducted by the Department at
44 sites along the west side of the San Joaquin Valley.
Virgin as well as irrigated sites were sought to evaluate
the variation in concentrations of nitrogen in the soil
profiles. Nitrate-nitrogen was found in all virgin soil
profiles sampled. The highest concentrations (saturation
extracts) were found in soil samples taken from virgin
profiles of Panoche and related soil series in the central
area. All virgin sites of Panoche and related soils
averaged about 97 mg/1 in the 3- to 10-foot tile zone
(ranging from 8 to 234 mg/l).
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Deep boring investigations conducted by soil scientists of
the Agricultural Research Service (ARS) also revealed high
levels of nitrogen (up to 225 mg/1) in Panoche soil profiles
along the west side of the San Joaquin Valley. Further
investigations by ARS showed very high concentrations of
nitrogen in parent materials of the Panoche soils. Average
nitrogen concentrations of the various parent material strata
ranged up to 2,000 mg/1 in 1:1 soil-water extracts.
Irrigated sites of different soil series contained less
nitrogen in the soil than virgin sites of the same series.
Eleven irrigated sites of Panoche soils averaged 37 mg/1 —
60 mg/1 less than the virgin Panoche soils. Nitrogen concen-
trations in samples collected from five irrigated Panoche
sites (25 borings) in the Federal San Luis Unit Service Area
(SLUSA) by the United States Bureau of Reclamation (USER)
averaged 19 mg/1 overall and ranged from 5 to 35 rag/1
between sites. Although these concentrations were somewhat
lower than those found by IMR, one site of the Lost Hills
series (which is closely related to the Panoche series) had
the highest average concentration found (109 mg/l).
Alluvial fan soils of the two northern areas appear to
contain less nitrogen than those of the central area. Much
lower concentrations were found in samples collected from
the Sorrento and related soil series. Nitrogen levels
averaged 25 mg/1 and ranged from 2 to 59 mg/1 for the five
sites sampled. . .
All of the basin rim soils investigated were irrigated.
Average nitrate-nitrogen levels ranged from 1 mg/1 to 171 mg/1
and averaged about 37 mg/1. Out of the eight basin rim sites
sampled, two contained high levels of nitrogen (more than
100 mg/l). The other six were low (less than 5 mg/l).
Higher concentrations were found by USER in some of the
irrigated soils of the Federal San Luis Unit Service Area.
The Oxalis series, which comprises the major portion of the
basin rim soils in the area, averaged 64 mg/l for the four
sites investigated and ranged from 5 to 206 mg/l between
sites. The other basin rim soils in the area averaged less
than 10 mg/l nitrate-nitrogen for the 3- to 10-foot tile zone.
Comparisons were made between the nitrogen observed in tile
drainage and that found in field moisture samples (porous
cups) and soil samples (saturation extracts) collected from
the same tiled fields. The comparisons showed that in three
out of four cases nitrogen was higher in the field moisture
samples than in tile drainage from the same field. Satura-
tion extracts prepared from soil samples were, however, about
30 to 40 percent lower than the average concentrations found
in the tile drainage.
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At this time, predictions of nitrogen from future-drained
areas based on nitrogen in soil samples or field moisture
samples can be made only with additional field study and
extensive correlation to existing tile drainage.
In summary, the one thing that can be said about tile
drainage is that its nitrogen content will vary greatly
between certain areas and also during the seasons. The
magnitude of variability depends basically upon three things:
(1) the particular kind of soil a tile system is associated
with and its physical location, (2) the irrigation pattern,
and (3) to a lesser extent, the type of crop being grown.
Although nitrogen levels from individual systems cannot be
accurately predicted from year to year, the Department is
reasonably certain that nitrogen levels in future drainage
can be predicted from the composite drainage of existing
tile systems in the San Joaquin Valley.
Phosphorus (phosphate-phosphorus)
Phosphate (orthophosphate) is the major phosphorous constit-
uent found in tile drainage of the San Joaquin Valley. Very
low concentrations of organic phosphorus were found because
of the low organic content of the tile drainage. Laboratory
analyses revealed that concentrations of orthophosphate in
tile drainage were essentially the same as total plus organic
phosphorus. For this reason emphasis in this report is given
to orthophosphate, which is referred to as phosphorus.
Phosphorous concentrations averaged 0.09 mg/1 in drainage
composited from valley tile systems during 1962 to 1969.
According to the available data, there are no indications of
long-term changes in phosphorus. Phosphorus from the Tulare
Lake area averaged 0.69 mg/1 — seven times higher than
drainage from either of the two northern areas or the central
area. Concentrations averaged less than 0.1 mg/1 in the
composited drainage from any one of these three areas.
The high levels of phosphorus in drainage from the Tulare
Lake area are suspected to be due to unusual source materials
contained in the soils. Analyses of the soils do not indicate
high concentrations of phosphorus, but there is an abundance
of phosphorous-bearing fresh water shells in the soil profiles
from that area. It is suspected that anaerobic conditions
exist in the saturated subsoils of the lakebed which create
an environment conducive for the release of phosphorus
from the shells and their related organic remains.
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Seasonal variations of phosphorus in the composited tile
drainage were comparable to that of nitrogen; that is,
summertime decreases were attributed to dilution in the soil
caused by irrigation. The highest average concentrations
were observed in January '(about 0.2 mg/l); the lowest
occurred in July (about 0,09 mg/l).
In conclusion, the present composite drainage from the major
tiled areas investigated is not indicative of phosphorous
concentrations in future valleywide drainage. Phosphorous
concentrations could increase as a result of drainage from
other lakebed areas having soils similar to that in the
Tulare Lake area. Based on predicted drain flows for the
year 2020, average concentrations in the drainage would be
0.23 mg/1.
Total Dissolved Solids
Total dissolved solids (TDS) averaged 3,625 mg/1 in the
combined valley drainage for 1962 to 1969. Long-term changes
between years were very small; TDS averaged 3,100 mg/1 for
1967, 3,200 mg/1 for 1968 and 3,550 for 1969. Higher
average concentrations were observed for drainage composited
during the earlier studies when only a few tile systems from
the Gustine-Mendota area were investigated.
TDS concentrations, however, did vary in drainage from
Individual tile systems. The levels ranged from 1,320 mg/1
to li|,600 mg/1 for intensively monitored tile systems. A
few isolated tile drains were found to be much higher in TDS;
for example, one experimental tile system exceeded 100,000
mg/1 at the lowest flows.
Seasonal and areal variability of TDS was great for drainage
composited from the major tiled areas. TDS averaged about
3,500 mg/1 in the winter and decreased to about 2,500 mg/1
during the summer.
Drainage from the central area (^1,130 mg/l) and southern
area (3,760 mg/l) was much higher in TDS than the drainage
from tile systems located in the two northern areas.
Drainage from the Byron to Westley area averaged 2,170 mg/l -•
the Westley to Gustine area averaged 2,7*10 mg/l.
TDS concentrations have been predicted to decrease signifi-
cantly in future drainage from the San Joaquin Valley.
Although long-time changes were not observed in the data
available during this investigation, it is believed that a
decrease in TDS would be inevitable if the existing monitor-
ing program was continued for a longer period.
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Discharges
The average annual tile discharge from 1966 through 1969 was
1.4 acre-feet per acre (ac-ft/ac) from the tiled areas
studied.
Long-term changes in the average tile discharge were not
observed during the more intensive investigations. This
relatively high discharge figure can possibly be attributed
to the fact that there is no way of knowing exactly how many
acres are actually drained by a given tile system. Land
adjacent to tiled fields or lying upslope some distance
from a tiled area is often drained by the tile system.
After adjoining fields are tiled, it is expected that the
average annual discharge would decrease significantly.
The average monthly discharge from valley tile systems
ranged from 0.05 ac-ft/ac in the winter months (December and
January) to 0.2 ac-ft/ac during July.
Plows from individual tile drains differed widely. Total
annual discharge ranged from a low of 0.3 ac-ft/ac to a high
of 17.3 ac-ft/ac for tile systems investigated in 1968. In
1968 it appears that about 14 percent of the tile systems
investigated discharged more water than was applied for
irrigation, assuming an average application rate of
3.0 ac-ft/ac/yr.
Tile systems in the Byron to Westley area discharged an
average of 2.3 ac-ft/ac/yr for a two-year period, which was
twice that discharged from the Gustine to Mendota area.
Discharges from the Westley to Gustine area (0.69 ac-ft/ac/yr)
was close to that observed from tile systems in the Tulare
Lake area (0.57 ac-ft/ac/yr).
Although tile discharge varies greatly between tile systems
and major tiled areas depending upon soil conditions and
irrigation, the average discharge from a large area of
drainage systems can be expected to remain rather constant
from one year to the next.
Conclusions
Nutrient (nitrogen and phosphorous) concentrations in
tile drainage composited from the San Joaquin Valley can
be expected to be close to the values previously predic-
ted by the Department of Water Resources in Appendix D,
Bulletin No. 127, "Waste Water Quality, Treatment, and
Disposal", April 1969.
7
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2. On the basis of observations made during this investiga-
tion, nutrient concentrations in the tile drainage from
the San Joaquin Valley are not expected to change
appreciably within the next 50 years.
3. Nutrient concentrations and total dissolved solids in
composited drainage can be expected to vary inversely
with the seasonal application of irrigation water.
M. Dilution and denitrification are highly suspect as the
reasons for decreases in concentration of nutrients and
TDS in tile drainage during the summer.
5. Denitrification is believed to be the main reason for
low nitrogen concentrations in tile drainage from the
basin rim and basin soils.
6. The areal variability of nitrogen found in the tile
drainage is more dependent upon the particular soil
series and the physiographic position of the tile
systems than on agricultural influence.
7. The relative concentrations of nitrogen in tile drainage
from future tiled areas can possibly be predicted on the
basis of current tile drainage data, along with a
representative soil-nitrogen sampling program.
8. High phosphorous concentrations in tile drainage from
certain areas is attributed to indigenous quantities in
the soil made available by anaerobic soil conditions.
9. The quantity of drainage from a given area depends more
on the interrelationships of physiographic position,
soil stratigraphy and texture, and irrigation than on
irrigation alone.
8
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SECTION II
INTRODUCTION
This report describes the nutrient monitoring investigations
conducted over a period of ten years, from 1959 through
1969* the greatest emphasis being placed on the more inten-
sive investigations conducted recently.
Intensive investigations of nutrients in San Joaquin Valley
agricultural subsurface (tile) drainage were undertaken from
May 1959 through June 19&9> as part of the San Joaquin
Valley Drainage Investigation (l).
Area of Investigation
Drainage problems have existed for some time in many areas
within the trough of the San Joaquin River Basin and the
Tulare Lake Basin. However, during the last two decades
severe high water table conditions have Increased in many
areas where subsoil permeability is restricted and irriga-
tion has been intensive. Existing high salt concentrations
in subsurface water have caused extensive damage to crops
and rendered large acreages nonproductive. The use of sub-
surface drains as a practical means of alleviating high
water table conditions was initiated in the San Joaquin
Valley 20 years ago, following many years of successful
operation in the Imperial Valley.
Now more than 3^>000 acres are directly subjected to tile
drainage within the San Joaquin Valley; a much larger acre-
age may actually be benefited because tile systems intercept
lateral movement of subsurface waters from adjacent and
upslope areas. Installation figures obtained from the U. S.
Department of Agriculture indicate that new tile systems
have been installed at an average rate of about 200,000
linear feet per year in the valley areas. In addition, a
massive network of tile drains covering 300,000 acres has
been planned by the Westlands Water District for the Federal
San Luis Unit Service Area in western Fresno and Kings
Counties. Although drainage problems exist to some extent
in every county on the valley floor, tile installation has
progressed most rapidly in portions of San Joaquin, Stanis-
laus, Merced, Fresno, and Kings Counties. Tile drains in
San Joaquin County are situated along the west side, between
the towns of Byron and Westley; in Stanislaus County,
between Westley and the town of Gustine; in Merced County
and northwest Fresno County, between the towns of Gustine
and Mendota; and in Kings County, west of the City of
Corcoran, on the northeastern shore of the old Tulare lakebed,
-------
These major tiled areas are geographically separated on the
valley floor as shown in Figure 1 and ar.e differentiated
from one another in this report by the towns named above.
When deemed appropriate, tiled areas are referred to as the
northern, central, and southern areas, which correspond to
the Byron-Gustine (includes both northernmost tiled areas),
Gustine-Mendota, and Tulare Lake Basin areas, respectively.
Isolated Tile Systems
A number of isolated tile drainage systems exist throughout
the major drainage problem areas and also in several other
poorly drained areas, including certain portions along the
east side of the Valley at the base of the Sierra Nevada
foothills. Most of these systems are isolated, many of ^
representing localized drainage conditions not particularly
representative of the surrounding area.
Objectives
The objectives of the monitoring investigations were to:
(l) determine the average nutrient concentrations in tile
drainage and the average flows from existing tile drainage
systems of the San Joaquin Valley, (2) determine the magni-
tudes of annual, areal, and seasonal variability of nutrient
concentrations and discharges of tile drainage throughout
the major tiled areas of the San Joaquin Valley, (3) if
possible, correlate observed nutrient concentrations and
tile discharges to agricultural practices, and (4) determine
whether soil conditions exist that may influence nutrient
concentrations or flows of tile drainage systems.
10
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FIGURE I • MAJOR TILED AREAS OF THE SAN JOAQUIN VALLEY
11
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SECTION III
TILE DRAINAGE IN THE SAN JOAQUIN VALLEY
Simply stated, a subsurface drainage system consists of a
deep open drain or some form of conduit so placed in the
soil that it effectively drains subsurface water away from
the root zone within a field. Subsurface drains and tile
drains are used interchangeably in this report and refer to
tile, concrete, plastic, or other pipeline material used as
conduit.
Several interrelated factors influence the quantity and
quality of tile drainage from different parts of the Valley.
These factors are: (l) tile drain design, (2) materials
used in construction, (3) effective placement, (4) soil
characteristics, (5) agricultural management, (6) precipita-
tion, and (7) age of installation. These factors will be
discussed in the subsections that follow.
Historic Background
The first tile drainage systems in the San Joaquin Valley
were installed at Kearney Park in Fresno County in 1905.
For many years thereafter, very few tile systems were
installed elsewhere. The first tile drains along the west
side began to appear in the central area near the town of
Firebaugh around 1950> following 20 years of successful
operation in the Imperial Valley. During the next decade,
many systems were installed, not only in the vicinity of
Firebaugh but also in the northern and southern areas near
the towns of Tracy and Corcoran, respectively. During the
last decade more tile systems have been installed nearly
every year near Firebaugh and Tracy; the installation of
tile systems in other areas has been somewhat sporadic.
Tile Drain Design
Tile drain designs have changed very little from the first
known tile system (2) installed near Geneva, New York, in
1835. Considerable work has recently been accomplished on
tile drainage theory by many investigators (3)> but practical
application at this time has been thwarted by efforts to
deal economically with variable soil conditions (i.e.,
stratigraphy, barrier depth and permeability) that exist in
west side soils. In some cases the proximity of canals and
local physiographic features such as rivers, sloughs, and
depressions may be influential in determining the design
13
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criteria. However, the cost of construction still plays an
important part In determining the final design. Many tile
systems are installed in a piecemeal fashion. That is,
laterals are added whenever it is economically feasible for
a farmer to do so.
In the San Joaquin Valley, two basic tile system designs are
generally used: (l) the "interceptor" type, which is a
single-line drain placed on the periphery of a field to
intercept or reduce lateral movement of water, and (2) the
"total relief" type, which consists of a large number of
closely spaced laterals (distances vary from 200 to 400 feet)
designed to alleviate existing high water table conditions
within an entire field.
These two types of tile
system layouts are illus-
trated in Figures 2 and 3.
Modifications of Inter-
ceptor type drains have
led to the use of other
terms, such as "partial
relief", which refers to
single-line or interceptor
drains in which one or two
laterals are added to
alleviate specific high
water table conditions
within a field. Distances
between laterals in these
systems usually exceed
400 feet; 600- to 800-foot
distances are common.
FIGURE 2
INTECEPTOR SYSTEM
FIGURE 3
TOTAL RELIEF SYSTEM
The term "perimeter interceptor" is applied to fields
surrounded by a single-line drain, several of which exist in
the area studied.
Various design modifications have been made to adapt tile
systems to particular drainage conditions or economic situa-
tions. Consequently, many systems cannot be adequately
described by the above terminology.
Materials, Construction, and Installation
The sustained performance of a tile system is governed to a
great degree by the type of materials used in construction
and the methods of installation. Materials used in construc-
tion of tile systems In the San Joaquin Valley have been
somewhat limited to those products available from local
manufacturers. The selection of materials depends mainly on
recommendations made by local work unit offices of the Soil
-------
Conservation Service, U. S. Department of Agriculture and
tile system contractors; however, final decisions are
usually made by individual farmers. The materials, construc-
tion, and methods of installation are discussed in the
subsections that follow.
Conduit. In the past, the term "tile drain" referred to a
drainage system in which red clay tile conduit was used.
The term as used locally refers to drainage systems using
both concrete and tile. Prior to 1969, concrete pipeline
was used almost exclusively in all major tiled areas.
Although it usually costs more than red clay tile or plastic
conduit, its tongue-and-groove construction resists deforma-
tion by the soil more than does the "butt joint" clay tile,
which makes it more desirable from a maintenance standpoint.
The use of plastic as conduit is rapidly becoming popular
because it is less expensive than concrete pipeline. Several
large drainage systems constructed of plastic were installed
in the Gustine-Mendota area in 1969 and 1970.
Concrete and tile conduit are segmented, usually in sections
whose lengths depend on the diameter. The diameter of
conduit to be used is chiefly determined by the size of the
drainage system and the expected peak discharge. Plastic
conduit is available in several different diameters and
usually comes in a more or less continuous roll which is
perforated throughout its length. Plastic drains installed
recently in the Gustine-Mendota area appear to perform as
well as the concrete and clay tile systems.
Filter Materials. To operate satisfactorily, subsurface
drainage systems require a filter medium. Sand and gravel
placed around the conduit during installation have proven
to be quite successful in most major tiled areas. The kind
of material and the amount needed seem to be a matter of
controversy. Investigation of tile performance by Johnston
and Plllsbury (4) has shown that the amount of filter sand
has no relationship to the efficiency of drain operation,
providing it is no less than 6 and no more than 18 tons per
100 linear feet of conduit.
Soil Conservation Service engineers (5) have reported better
results with pea gravel than with graded sand or gravel in
tile systems located near Tracy.
Contractors and drainage specialists have reported instances
of tile drainage systems which have ceased to function
because improper filter materials were used. Fiberglass,
used as envelope material in certain experimental plots near
Firebaugh, has been found in a deteriorated condition after
only a few years in the soil. Inspection of excavated
15
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sections of pipeline has often shown that systems installed
without filter material and backfilled with soil were
"silted in" or were grossly restricted by crop roots.
Similar conditions have also been reported for systems which
have been improperly vented. Vented systems are those which
have vertical sections of pipeline installed at intersec-
tions of laterals and the mainline. Cases have been
reported where tile system laterals without vents develop a
vacuum condition that hastens silting, root growth, and the
formation of bacterial sludge. All tile systems monitored
during this investigation had sand or gravel filter
materials; only a few of the systems monitored were provided
with vents.
Installation. The drainage pipelines are usually buried at
a predetermined depth and gradient from 5 to 9 feet below
the surface of the soil. The specific depth at which pipe-
lines are installed, which is believed by some Soil Conser-
vation Service engineers to be quite critical, varies from
one area to another, depending upon soil conditions (texture,
stratigraphy, and topography).
Most of the tile systems in the Gustine-Mendota area have
been installed at an average depth of about 7 feet. In the
Byron-Westley area, many tile systems have been installed at
9-foot depths. One tile contractor claims that deeper
drains allow more distance between laterals because of
greater drawdown, which permits a lower water table and a
more consistent drainage between irrigations.
Tiling operations may differ greatly depending on the type
of conduit materials being used. During the installation of
concrete pipeline, constant mechanical pressure is applied
to the segmented pipe by tiling machines to minimize deforma-
tion of the pipe during backfilling and during later subsi-
dence. Some tiling machines employ the use of a television
camera to monitor the placement of conduit (center of photo-
graph, Figure 4).
Plastic conduit is now Installed with the same basic
machinery used to install concrete conduit. The use of
hydraulic equipment has been eliminated because alignment is
not as critical a factor in the installation of plastic pipe
as in the installation of concrete pipe. Therefore, Instal-
lation time is decreased. New methods of plastic pipeline
installation are being developed wherein long strings of
conduit are fed into preformed tunnels made by a large
subsoillng device.
16
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FIGURE 4. CONCRETE PIPELINE INSTALLATION
Sumps and Outlets
Free-flowing outlets are necessary if water tables are to be
maintained at desired levels. Subsurface flow in most tile
drains is carried in various laterals to a main collector
line located at the low end of a tiled field, and drains
into an open ditch or a concrete collector reservoir (sump).
A typical tile system layout commonly found on the west side
of the Valley is shown in Figure 5-
Sumps are constructed of 7-foot diameter concrete rings
which are 3 feet high; when placed one above the other these
rings form a sizable reservoir for collection of wastewater.
Water levels are usually maintained below the tile outlets
by automatically controlled pumps. Tile drainage outlets
and level control devices are accessible through a manhole
located on top of the sump. A typical sump is shown in
Figure 6.
Many tile drains in the northern and central areas have
"free" or "gravity" type outlets that empty into open
drainage ditches. A few smaller sumps constructed of 3-foot
diameter pipeline have been installed near Tracy and in the
Tulare Lake area. These pipes are usually placed underground
in a horizontal position.
17
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FIGURE 5-TYPICAL TILE DRAINAGE SYSTEM
WEST SIDE OF THE SAN JOAQUIN VALLEY
-
^
FIGURE 6. CONCRETE SUMP
18
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Effective and Critical Placement of Tile Drain
Whenever possible, tile drainage systems are strategically
placed within a field or area to alleviate high water table
conditions and to prevent their recurrence. At times,
subsurface water moving laterally through an aquifer can be
intercepted by critical placement of the conduit, instead
of by tiling an entire field (total relief). The choice of
method Is usually decided by farm operators who are guided
by advice from drainage specialists. Several tile drainage
systems in the northern area have been strategically located
to intercept lateral water movement through former submerged
streambeds. Many tile systems in the Gustine-Mendota area
have been placed to intercept lateral movement from canals.
Physiographic Positions
The drains located along the west side of the San Joaquin
Valley are found associated with soils occupying three
commonly recognized physiographic positions (6). Those
positions are the "alluvial fan", which extends from the
base of the surrounding foothills nearly to the edge of the
valley floor; the "basin rim", a relatively narrow band of
alluvial, saline soils which lie between the more recent
alluvial soils and the soils of the basin; and the "basin"
or lowest central part of the valley floor. The alluvial
fan is often divided into the "recent fan deposits", usually
occurring in low-lying sites subject to fairly recent stream
overflow, and "older alluvial fans" occurring at higher
elevations. The manner of soil formation causes soil charac-
teristics to differ widely from one physiographic position
to another.
Recent Alluvial Pan
Soils in recent alluvial fans have been deposited by recent
flooding of intermittent streams from older alluvium and
parent materials at higher elevations. They are derived
from out-wash materials, mostly sandstone and shale rock,
and generally owe their characteristics to the character of
the stratified parent material. Time has not permitted the
formation of well-developed horizons within the solurn.
(Developed soils are those which exhibit clay movement from
the surface horizon and clay accumulation in the lower
horizon.)
19
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Older Alluvial Fan
Older alluvial soils are medium-textured and have moderately
or sometimes strongly developed subsoils. The parent
material of these deposits is alluvium that has washed from
mixed sedimentary hills of the Diablo Range. These older
fans have deeply entrenched drainage ways, so new material
is seldom deposited on the surface. Weathering and soil
development have caused formation of rather well-defined
soil layers.
Basin Rim
Parent materials of soils in this position are the same as
those of the older and recent alluvium; stratigraphy and
texture are often similar to the lower portions of the
recent alluvial fans. The prominent differences are soil
color and greater concentrations of salt in the soil profile,
Structural differences may also occur when salt concentra-
tions are predominantly the sodium ion.
Soils in this position are usually fine-textured and are
generally characterized by moderate to extremely strong
concentrations of alkali in the soil profile. Salts accumu-
late at this position because of (l) leaching and runoff
from soils at higher elevations and consequent trapping in
depressions on the rim and (2) because of a long continuing
high water table under the basin rim soils. The second of
these is perhaps the most important. Evaporation at the
soil surface and transpiration by native vegetation brought
large quantities of salts into the surface soil and left
them there.
Basin
This group of soils comprises part of a large prominent
basin that extends nearly the entire length of the San
Joaquin Valley. Parent materials of soils in the basin
position result primarily from eluviation from mixed granitic
sediments originating in the Sierra Nevada on the east side
of the Valley that were deposited by waters of the San
Joaquin River, Fresno Slough, and the Kings River. Soils
which lie within the basin are easily distinguished from
soils in other positions. Basin soils are dark, fine-
textured, and poorly drained.
20
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Tiled Acreages within Physiographic Positions
A much greater acreage of tile has been installed in recent
alluvial fans than in older fans, basin rim, or basin
positions. The acreages shown in Table 1 represent all the
tile systems installed up to 1969 within the Valley from
Tracy to south of Bakersfield, including a few tile systems
on the east side of the Valley. These acreages were deter-
mined from scaled drawings on U. S, Geological Survey
quadrangle sheets, 7-1/2-minute series. Acreages are
estimates based on the actual areal coverage of the tile
laterals. Interceptor drains were allowed 40 acres for each
one-fourth mile of conduit, when isolated from other tile
systems.
TABLE 1
TILE ACREAGES WITHIN MAJOR PHYSIOGRAPHIC POSITIONS
OF THE SAN JOAQUIN VALLEY FLOOR
1968
Physiographic Position I Tiled Acreage
Recent alluvial fan 17,078
Older alluvial fan 7,840
Basin rim 6,559
Basin 2,221
Total 33,698
Soils and Soil Characteristics
Soil characteristics are one of the most important factors
which determine the quantity and quality of drainage in tile
systems. A thorough picture of soil morphology and genesis
is necessary to understand the variable soil conditions that
exist along the west side.
Morphology and Genesis
The west side of the San Joaquln Valley, as referred to in
this report, refers to the vast expanse of soils on the
eastern slope of the Diablo Range. This area extends from
Tracy to south of Bakersfield. Physiography of this area
consists of gently sloping and coalescing alluvial fans that
extend from the base of the mountains to a "salt rim" zone
21
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or "basin rim" surrounding the "trough" of the valley floor.
Soils which occupy these different physiographic positions
have developed certain characteristics which vary, depending
upon the influence of one or more of the soil-forming
factors. These factors are climate, organic matter,, topo-
graphy, and time.
The present valley floor has been built up with recent
Quaternary stream deposits or with sediments of fluctuating
Pliocene lakes. These deposits were composed of eroded
materials transported from the drainage areas of the
surrounding mountains.
Because of the arid conditions on the west side, the composi-
tion of parent material prevails as the most important single
factor in the process of soil genesis. Soils that occupy
recent alluvial, older alluvial, and basin rim positions
have been derived from rocks of the Diablo Range. This
mountain range is composed of a series of calcareous and
gypsiferous sandstones, shales, and conglomerates of the
Cretaceous and earliest Tertiary (Eocene) periods. A minor
influent from relatively small areas of metamorphic rocks of
the Franciscan formation (Jurassic) is expressed in the red
coloring and basic tendencies of some of the alluvial soils.
The basin soils reflect the genetic influence of mixed acid-
igneous parent materials of the Sierra Nevada.
Description of Soils
Within the area of investigation, several distinctly differ-
ent soil series are associated with tile drain systems. A
soil series is a group of soils having horizons similar in
differentiating characteristics and arrangement in the soil
profile, except for texture of the surface portion, or, if
genetic horizons are thin or absent, a group of soils that,
within defined depth limits, is uniform in all soil charac-
teristics diagnostic for series (7). Variations of surface
texture give rise to a "soil type", the latter being a
combination of the soil series name and the soil surface
texture, for example, "Panoche fine sandy loam". Different
soil series may develop from the same parent material
depending on the degree of influence of one or more soil-
forming factors. Soils occupying different physiographic
positions may have formed under similar environmental condi-
tions except for parent material, which can significantly
affect the chemical and, in many cases, the physical charac-
teristics of a soil.
Generalized descriptions condensed from U. S. Department of
Agriculture soil surveys are given for individual soil
series in this report. Soil characteristics which could
22
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possibly affect the quantity and quality of tile drainage
are described in' the subsections that follow.
Acreage subjected to tile drainage and number of- tile
systems for each soil series and their respective physio-
graphic basin position are given in Table 2.
TABLE 2
ACREAGES!/ AND NUMBER OF TILE SYSTEMS WITHIN
DIFFERENT SOIL SERIES AND PHYSIOGRAPHIC POSITIONS
1968
Physiographic: Soil
Position : Series
: Number of
: Systems
Recent
Alluvial
Fan
Older
Alluvial
Fan
Basin
Rim
Basin
Panoche 51
Sorrento 11
Panhill 6
Foster 1
Subtotal 29
Lost Hills 26
Rincon 15
Ambrose 13
Subtotal 54
Oxalis 37
Willows 4
Levis 6
Lethent _2
Subtotal 49
Tulare 6
Columbia 2
Sacramento 2
Hacienda _1_
Subtotal 11
Grand Total 183
Estimated
Acre'age
8,629
3,206
650
_ 73
12,558
4,395
2,115
1,330
7,840
4,959
800
150
6,559
1,250
160
153
120
1,683
28,64oi/
I/ Acreage lying outside the major tiled areas
is excluded.
23
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Soils on Recent Alluvial Fans. The Panoche and Sorrento
soil series both occupy extensive recent alluvial fans along
the west side. Tile drainage systems are well-represented
in these two series. Only a few tile systems are located in
the Panhill series and only one system in the Foster series.
All these soils are closely related in mode of formation.
Soil-forming factors have not had time to act upon the soils,
which are usually deep and permeable and offer little or no
restriction to downward water movement in the upper portions
of the soil profile. However, these soils are stratified at
lower depths with sand, silt, and clay, the latter two causing
perching when they are irrigated heavily. Some evidence of
soil formation can be found in the Sorrento and Panhill soil
series; little or no soil development occurs in the Panoche
and Foster profiles.
As originally mapped in western Fresno County, the related
Panoche and Panhill soils were moderately affected by salt
and alkali. This is in contrast to the relatively salt-free
Sorrento series. Parent materials from sedimentary sources
are mainly sandstones and shales of the Coast Range.
Sorrento soils, which are located north of Gustine, are
slightly darker than are the Panoche or Panhill soils of the
central area. This may be due to the greater influence from
nonmarine parent materials found in the area (8).
Soils of Older Alluvial Fans. The Rincon, Ambrose, and Lost
Hills soil series occupy older alluvial fan positions in the
study area which have developed on valley fill material
derived from the same sedimentary sources as recent alluvium.
The main bodies of these soils are located short distances
from stream channels, but they are free from recent alluvial
deposition which has resulted from changes which occurred in
the main course of the depositing stream. Soils in these
positions have had sufficient time to develop a well-defined
subsoil in which clay and lime have accumulated. Permeabil-
ity is inhibited but not restricted in the subsurface;
however, the subsoils are often stratified and restriction
occurs at lower depths.
The Rincon soil series is genetically related to the more
recent Sorrento series in the northern area. These soils
are somewhat darker and contain less alkali and other salts
throughout the soil profile than does the Lost Hills series
of the central area.
The Ambrose soils normally have fine-textured surfaces and
heavy-textured subsoils that restrict the penetration of
roots and water. The substratum, which ranges, from 30 to
60 Inches below the surface, consists of stratified
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calcareous sediments which have a lighter texture. These
soils are normally free from alkali and other salts, except
on the lower portions of the alluvial fan where drainage is
restricted. Parent materials are a mixture of marine and
nonmarine sediments.
The soil series having the greatest amount of tiled acreage
is the Lost Hills series, followed by the Rincon and the
Ambrose series.
Soils of the Basin Rim Position. Four major series make up
the bulk of basin rim soils In the study area. These are
Oxalis, Lethent, Levis, and Willows. These soils occur in
the Gustlne-Mendota area at the outer edges of alluvial
fans along the shoreline of a former shallow inland lake.
Parent materials are fine-textured, calcareous alluvium that
originate from softly consolidated sandstones and shales.
These soils are fine-textured, and, unless modified by
irrigation, are characterized by strong concentrations of
alkali and gypsum throughout the profile.
The most extensive basin rim soil belongs to the Oxalis
series, which is associated with soils of the Panoche series
but is typically darker, finer textured, and subject to slow
surface drainage. The substratum is very often stratified
with fine silty material that creates temporary perched
water conditions.
The Lethent, Levis, Willows, and Oxalis soil series are very
closely related arid were originally mapped as a soil complex.
Many tile drains are located in the abundant Oxalis series.
Soils of the Basin Position. Soils lying within the basin
or trough position are generally fine-textured and dark and
contain less surface alkali than do the soils of the basin
rim. Parent materials are derived from mixed granitic
sources from the Sierra Nevada.
The largest tiled acreage within the basin position Is the
Tulare series, which occupies the Tulare lakebed. Soils of
this area are flat and poorly drained and at one time
supported a great growth of tules. Salts contained within
the highly stratified profiles tend to move to the surface
unless prevented by frequent irrigation or ponding.
The soils of the Columbia series, represented by two systems
located in the northern area, have been subject to frequent
-------
overflow; therefore, the profiles are relatively salt-free
and somewhat stratified. Parent materials consist of mixed
rock sources.
The Sacramento series, which is located north of Tracy, is
also characterized by frequent overflow. These soils
usually have a high organic matter content. Very little
acreage has been subjected to tile drainage.
The Hacienda series is represented by a small acreage in the
Tulare Lake area. These soils are more stratified and more
strongly developed than are those in.the Tulare series.
Climate
Climate greatly affects the quantity and quality of tile
drainage along the west side. Heavy rainfall causes leaching
of surface soil and, when excessive, may cause increases in
tile flow and changes In quality. Too little rain and high
temperatures result in Increased irrigation, which directly
influence tile discharge and its quality.
Temperature
The climate along the west side of the San Joaquin Valley is
typically arid, with maximum daytime.temperatures frequently
exceeding 100°F in July and August. Average annual tempera-
tures vary only slightly from one climate station to another;
differences between year,s.are also small, as shown in Table 3
TABLE 3
AVERAGE ANNUAL TEMPERATURE ,
AT SELECTED WEATHER STATIONS i/
ALONG THE WEST SIDE
Location 1959 i960 1961 1962 1963 19& 1965 1966 196? 1968 1965
Tracy Carbona 62.0 61.6 61.2 59.7 59-5 6o.T 6o.l 61..7 6l-3 6l.2 6lA
Westley Iffi 61*.3 6U.9 6l.7 60.5 6l.O 63.0 62 A 59.2 6l.l 62.8
Newman 6lA 6i.2 6l.o 6o.l 59.7 6o.2 60.3 6l.5 60.7 60.9 6o.5
Los Banos 63.5 62.1* 62.2 6l-3 60.7 60.7 61.6 62.7 62.1 62.8 6lA
Corcoran NR 63.3 62.k 61.8 61.2 6l.8 61.8' 63-3 62.6 62.8 62.1
I/ U. S. weather Bureau, Department of Water Resources, and cooperative stations.
NR = No record.
26
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These data were obtained from a weather station located in
the heart of well-established agricultural areas. Average
maximum temperatures are higher and minimum temperatures are
lower in these areas than on the large alluvial fans adjacent
to the foothills where irrigation is limited. According to
studies (9) conducted by the Department of Water Resources,
topography appears to influence air temperature extremes
more strongly than does agricultural environment.
Evapotranspiration and
evaporation reach their "
upper limits during July
and August. Irrigation
in the Valley increases
rather consistently with t
rising temperature. |
Figure 7 shows monthly |
average temperatures at f
Los Banos for 1968.
Pr e c ip it at ion
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT MOV DEC JAN
1968
FIGURE 7-MONTHLY AVERAGE TEMPERATURE AT LOS BANOS
Less than a quarter inch
of precipitation falls
along the west side
between the months of June and September; consequently,
relative humidity remains low during these months. High
temperatures and prevailing northwest winds combine to
produce very high rates of evaporation and evapotranspira-
tlon, which means most crops need intensive irrigation.
Precipitation is somewhat irregular from Tracy-Carbona in
the north to Corcoran in the south. The amount of precipi-
tation decreases to the north and to the south from Gustine.
Influence from coastal storms can be seen in the data
presented in Table 4. According to the data, for the period
of study, precipitation as far north as Tracy has not
greatly exceeded that recorded at Corcoran.
Although the data show higher precipitation toward the
trough of the Valley, rainfall seldom exceeds 6 inches over
much of the area adjacent to the foothills of the Diablo
Range.
Agriculture and Agricultural Practices
The types of agriculture practiced in an area may influence
the quantity and quality of tile drainage. For instance,
tiled areas that are devoted mainly to dairy farming receive
27
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TABLE 1*
ANNUAL PRECIPITATION
AT SELECTED WEATHER STATIONS
ALONG THE WEST SIDE
Location 1959 1960 l<>6l 1962 1563 19& 1965 1966 1967 1968 1969
Tracy Carbona 7.71 7-30 7. It? 8.51 c.U? 7.97 10.18 6.39 10.79 I1*-31 10.22
Westley 9.78 8.12 7-92 10.87 12.57 8.8l 10.68 6.70 10.28 9.55 13.31
Newman 11.13 8.8l 8.78 10.39 lk-95 9-39 H-51* 7-75 11.kk 8.80 16.77
Gustine 11.23 10.52 NR NR 15-38 9.00 12J+3 7.22 11.91 9-60 17-22
Los Banos 6.56 8.16 7.12 9.3!* 10-93 9-16 10.65 6.87 9.21 7.^5 lk.k2
Dos Palos 5.U8 7-93 6.58 8.13 10.27 6.95 8.97 U.70 7.60 9-26 11.9!*
Mendota Dam 5.28 7.13 7.25 7.^8 8.70 6.17 7.29 5.1*1 9.06 7.80 11.72
Corcoran 3-19 6.7** l». 66 5.89 8.92 5.51 6.30 5.23 6.96 6.11 12.66
I/ U. S. Weather Bureau, Department of Water Resources, and cooperative stations.
NR = No record.
little commercial fertilizer but are heavily irrigated.
Highly diversified areas receive varying applications of
irrigation water but are apt to have a regular fertilization
program.
Agricultural trends may change fertilization and irrigation
programs, which may in turn affect the quantity and quality
of tile drainage.
Crops
Historically, farming practices on the west side have
followed those in the rest of the San Joaquin Valley,
evolving slowly in three distinct but overlapping stages.
These stages include a period of cattle and sheep raising, a
period of grain farming, and the present period of diversi-
fied agriculture dependent upon irrigation. Dry farming,
once popular for growing wheat, began to decline in favor of
irrigated grain and alfalfa sometime after 1900 when irriga-
tion districts began to form. Also about this time reclama-
tion districts in the Tulare lakebed were organized to
protect grain farmers from flooding waters of the Kings and
Tule Rivers.
28
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Through the years cattle raising and dairy farming have
continued to be an important part of the agriculture in the
area between Westley and Gustlne. The area around Byron and
Westley, once very popular for grain farmings has tended
toward truck crops and orchards in the last decade. Cattle
raising was also popular in the Gustine-Mendota area until
about 192O, when irrigation became more extensive. After
19^5> cotton, flax, and rice became more important and
cattle ranches disappeared. Cotton remains an important
crop, but truck crops have increased steadily even at the
expense of some cotton acreage. Cotton has been grown exten-
sively in the area from Tulare Lake to Gustine, although
very little cotton can be found north of the City of Newman
where lima beans are grown widely.
Double-cropping is a common practice in the Gustine-Mendota
area. Rice and barley are the most notable combinations;
however, several other combinations are found. The practice
of allowing a parcel of land to remain fallow over a period
of months has declined in this area due to the economic
demands that now are placed on the land.
Current Irrigation
Irrigated agriculture in the San Joaquin Valley has become
more prevalent as features of the Central Valley Project and
the State Water Project have developed.
Sources. In the study area, all fields investigated were
furnished with canal water imported chiefly from the Delta.
The exception was the Tulare Lake area, where water is
routinely pumped and recirculated through an elaborate
network of canal and levee systems. Water applied to a
given field depends entirely upon the individual management
of the farmer, the crop needs, and the quality of water
available. The amount of water needed to grow a particular
crop (consumptive use) is nearly the same from one end of
the Valley to the other. However, crop irrigation require-
ments (1O; differ from place to place, depending upon the
climate in an area and the type, maturity and condition of
crops grown. Adverse soil conditions such as coarse texture
and alkalinity can greatly affect the development of crops
in some cases and thereby affect their water requirement.
Types of Irrigation. In the study area, furrow irrigation
Is the method used most often on truck and field crops.
Grain and safflower crops are generally irrigated only once
during the year, if at all.
Preirrigation, a method for providing soil moisture in the
early spring for seed germination, is a common practice
throughout the entire area.
29
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Sprinkler irrigation is practiced on some of the highly
permeable soils on the west side, especially in the Gustine-
Mendota area. It is rapidly growing in popularity. The
check irrigation method is used for pasture, alfalfa, and
orchard crops. Rice crops, limited mostly to the central
area, are flooded during June through early August.
30
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SECTION IV
METHODS AND MATERIALS
This section describes the methods and materials used in
monitoring tile drainage systems for-the period of study.
Monitoring Tile Drainage Systems
A brief history of tile drain monitoring is presented to
show the necessity for an intensified monitoring program. A
greater emphasis was placed on the selection of tile drains,
field monitoring techniques, and collection of agricultural
and soils data during the more recent studies than in the
past.
Hi s t or i c al Moni t or ing
Initial Investigations of tile drainage began in 1959 as
part of the Agricultural Waste Water Quality Studies, a
cooperative program between the Department of Water
Resources and the Water Resources Center of the University
of California. During these studies, the emphasis was
placed on the quantity and quality of surface and subsurface
agricultural wastewater. The frequency of sampling for tile
systems at that time was somewhat limited; 104 nutrient
samples were collected from 29 systems over a four-year
period. Most of these systems (25 out of 29) were located
in the central area; the other four were located in the
northern area.
Samples were not collected from tile systems in 1964 and
1965. However, in 1966, seven tile systems were selected
for more intensified sampling in the central area. Later
the same year, reconnaissance investigations showed that
drainage from other tile systems in the same area contained
much higher concentrations of nitrogen than those currently
being sampled. At the same time, drainage from tile systems
in the Byron-Westley and Tulare Lake areas was found to be
lower in nitrogen concentrations. The foregoing investiga-
tions led to the eventual expansion of the monitoring
program to include as many as 40 individual systems in 196?
and 42 systems in 1968. Intensive investigations were not
initiated in the Byron-Westley area until May 196?; all
other major tiled areas were sampled for the full calendar
year. In 1968, all 42 tile systems within the major tiled
areas were sampled intensively for the entire year. In
addition, 18 satellite systems and a few isolated tile
31
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drains were also monitored, but on a less frequent basis.
The monitoring program was greatly reduced in 1969; samples
were collected on a monthly basis from only 20 tile systems.
Selection of Tile Drainage Systems for Monitoring
Large, well-designed tile drainage systems having good
agricultural management were quite easy to find during the
initial investigations when only a few systems were required
for study. However, selection became increasingly difficult
when a number of representative tile drainage systems were
sought with regard to specific soils, physiographic posi-
tions, and certain agricultural practices. These and other
factors were considered paramount in selecting an individual
tile drainage system to be monitored. These are listed in
their order of desirability.
1. Location. Several systems were chosen to represent
the four major tiled areas. Isolated systems and
satellite systems were chosen for supplemental data.
2. Size. Larger systems were preferred to smaller ones
in hopes of reflecting drainage from a large area of
soils.
3. Design. "Total relief" systems were chosen for
greater representation of soil conditions in prefer-
ence to "interceptor" type drains.
4. Agricultural Practices. Tile systems draining fields
having an active irrigation and fertilization program
were selected.
5. Physiographic Positions and Soils. Tile drainage
systems occupying different physiographic positions
and representing various soils were also selected.
6. Sumps and Outlets. Tile systems with sumps were
selected for convenience of sampling and flow
measurement.
7. Age. A range of ages from 1955 to 196? was selected.
Very few tile drains were installed in the Valley prior
to 1950.
Selecting tile drains was at times difficult, because very
few had all the desirable features. Generally, as many tile
drains with the foregoing factors were chosen as possible
within the major areas of interest.
32
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Acreages Monitored. The number of acres tiled was not
determined for the systems sampled from 1959 to 1963.
During 1966 approximately 1,5^5 acres were sampled in the
Gustine-Mendota area. Table 5 presents a summary of acre-
ages devoted to agricultural subsurface drainage systems and
acres sampled for nutrients within the major tiled areas of
the San Joaquin Valley in 196? and 1968.
TABLE 5
ACREAGE* TILED AND ACREAGE SAMPLED
FOR NUTRIENTS IN MAJOR TILED AREAS
Major Tiled Area
Byron to Westley
Weetley to Gustine
Gustine to Mendota
Tulare Lake Drainage District
TOTALS (MAJOR AREAS INVESTIGATED)
ALL OTHER DRAINAGE AREAS
(ISOLATED TILE SYSTEMS)
TOTALS
Acreage
Sampled
1967
1,68?
1,559
3,779
953
7,979
8U8
8,827
: Tiled
: Acreage
: 1967
U,55U
1,959
16,310
1,^3
2^,266
it, 998
29,2&
: Acreage
: Sampled
: 1968
1,93U
1,559
l*,879
1,273
9,&5
8U8
10,1*93
: Tiled
: Acreage
: 1968
^,775
2,139
20,3>»3
1,M*3
28,700
U,998
33,698
*Acreeges were estimated from scaled drawings on U.S.G.S. quad sheets
(1/1+ mile of interceptor line was assumed to drain 1»0 acres).
A few tile systems lying outside the major tiled areas were
also sampled. Acreages representing these systems are shown
separately in Table 5-
Tile acreage sampled increased from 196? to 1968.. due to the
addition of two new tile systems to the monitoring program;
also, several of the systems being sampled were expanded.
About 53 percent less acreage was monitored in 1969 than in
1968, due to a reduction in the program.
Table 6 summarizes the number of tile systems and acres
sampled in 1968 within different physiographic positions and
soil series. These tile systems are located within the major
tiled areas of the Valley and are the ones that were inten-
sively sampled. Acreages of isolated or satellite tile
drainage systems within specific positions or soils were not
determined.
33
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TABLE 6
TILE DRAINAGE SYSTEMS AND ACRES SAMPLED
BY SOIL SERIES AND PHYSIOGRAPHIC POSITIONS
WITHIN THE MAJOR TILED AREAS
1968
Physiographic :
Position :
Recent
Alluvial
Fan
Older
Alluvial
Fan
Basin
Rim
Basin
Soil Series
Panoche
Sorrento
Panhill
Foster
Rincon
Ambrose
Lost Hills
Oxalis
Lethent
Willows
Tulare
Sacramento
Hacienda
: No. of
: Systems
8
6
4
1
4
3
3
i\
2
1
4
1
1
•
I Acres
•
2,071
2,356
595
73
895
169
858
825
390
140
1,080
73
120
Total 42 9,645
Tile Monitoring Techniques
The monitoring program consisted of measuring tile discharge
and collecting samples of tile drainage for analyses of
nutrients and total dissolved solids. Mineral samples were
collected during the winter and summer of each year;
dissolved oxygen samples were only collected once during the
investigation.
Flow Measurement. Tile drainage discharge was measured
whenever samp1 e s were taken. Several methods were used to
determine the flow, depending upon the design of the individ-
ual tile outlet or discharge structure. All methods used
were volumetric procedures set forth in numerous standard
irrigation and drainage texts or necessary modifications of
the standard techniques.
The two methods used most in this study are the "bucket and
stopwatch method", used mostly for small flows, and the
"float method", a technique devised to measure very high
.34
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flows inside sumps. The latter method requires a. water
stage recorder float, an engineer's tape, and a stopwatch
(Figure 8).
FIGURE 8. "FLOAT METHOD" FLOW MEASUREMENT
Other methods employed under certain conditions included a
velocity meter, the "V" notch weir, pump rating and meter
readings, a parshall flume, and other combinations.
Nutrient Sampling. Samples were collected in plastic pint
bottles directly from tile outlets, sump pump discharge
pipelines (Figure 9), or from inside the sump and stored in
ice chests to inhibit possible denitrification during
transport to the laboratory.
Nutrient samples were collected on a weekly basis from all
the tile drainage systems included in the intensive investi-
gations (1966-60). Several "satellite" stations which were
located in the Byron-Westley and Gustine-Mendota areas were
sampled monthly during 1968. Isolated tile systems were
sampled weekly for eight months in the same year. Prior to
1966, occasional samples were collected at random from
several stations. A definite sampling frequency was not
established until 1966.
35
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FIGURE 9- SAMPLING METHODS — NUTRIENTS
Collection of Mineral Samples . Mineral samples were
collected rbutineTy during the initial investigations and
less frequently during the last few years of the study.
These samples were collected as back-up data for the nutrient
investigations and as a basis for determining other forms of
nitrogen and related constituents in the tile drainage.
Collection of Dissolved Oxygen Samples^ Effluent from
15 subsurface agricultural drainage systems was examined for
concentrations of dissolved oxygen (DO) to compare DO concen-
trations in drainage between tile systems in different major
tiled areas. Five systems were sampled in each of the
following major tiled areas: northern (Byron-Gustine),
central (Gustine-Mendota) and southern (Corcoran-Wasco).
Samples were collected from tile outlets, tile discharge
sumps, gravity drain pools and pump discharge pipelines. A
long, rigid plastic tube was used to obtain samples from
inside tile outlets.
Laboratory Techniques
As many as 300 samples per month were collected during 1967
and 1968. Nitrate and phosphate determinations had to be
made as soon as possible after sampling to prevent possible
36
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biological changes of nutrients in the samples. At times,
day-to-day changes of nitrogen concentrations in tile
drainage also had to be determined. The methods used to
determine nitrates, phosphates, and electrical conductivity,
and to prepare soil extracts are discussed in this
subsection.
NitrogenJDeterminations. Nitrogen determinations of tile
3rainage~~were made solely by the Department of Water
Resources' laboratory at Bryte, California, prior to 1966.
The Brucine method (11) is the accepted method used by the
DWR laboratory to determine nitrates.
During this investigation most of the nitrogen determina-
tions were made in the San Joaquin District water quality
laboratory by the cadmium reduction method of nutrient
analysis, which was determined to be sufficiently accurate
for monitoring nutrients in tile drainage from the San
Joaquin Valley. This method relies on the conversion of
nitrate to nitrite. It is basically a colorimetric deter-
mination using a photoelectric cell and a fixed wave length
filter. This method was selected for two reasons:
(l) because immediate analyses of a large number of samples
could be made rapidly with an accurate account of the
nitrate-nitrogen concentrations, and (2) nitrates consti-
tuted more than 90 percent of the nitrogen in the tile
drainage. (Organic and ammoniacal nitrogen was found to be
less than 1 milligram per liter in tile drainage according
to Kjeldahl analyses made by the DWR laboratory.)
The cadmium method was first used for determining the
general range of nutrients In the field. Accuracy and
precision were later improved, due to the availability of
better reagents and the development of a continuous standard-
ization and checking process. A "standard curve" was estab-
lished to maintain accuracy of the nitrate determinations
throughout the study. In order to do this, an array of
nitrate standards were obtained from the DWR laboratory that
ranged from 5 to 400 mg/1. Repeated tests were made on
these samples in order to determine the transmittance for
different standard concentrations. From these data a
"standard curve" was established to which samples containing
unknown concentrations could be compared. An average
standard deviation of less than 4.0 percent was achieved
time after time for a series of laboratory-prepared nitrate
standards that ranged from 15 to 280 mg/1.
As part of the checking process, approximately 5 percent of
the field samples were split between the two methods of
analysis. A statistical comparison showed a correlation
coefficient of 0.992 for 77 split samples; other spot compar-
isons also showed a close correlation between the two methods
37
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Phosphorous Determinations. A modified stannous chloride
method was used to determine phosphates (orthophosphate),
using the same colorimeter as that used in the nitrate tests.
Standardization curves were established and checked in the
same manner as in the nitrate tests in order to maintain
optimum control and the same high degree of accuracy.
In standard phosphate solutions ranging from 0.1 to 6.0 mg/1,
the average standard deviation was 3-6? percent of the mean.
A detailed account of the methods used in determining
nutrients, the techniques used for maintaining accuracy and
precision, and statistical comparisons made during the
course of the investigation is in the Department's files.
Electrical Conductivity. A conductivity bridge was used to
determine the electrical conductivity (EC) of the tile
drainage water and soil extracts. These tests were run in
the laboratory along with the nitrogen and phosphate deter-
minations. A factor of 0.7 was used in converting EC values
(micromhos x 10~°) to total dissolved solids (TDS, mg/l).
This is an average factor determined from mineral laboratory
reports.
Soil Extracts. Nitrate analyses (cadmium reduction method)
of soil1 samples were made on extracts that were suction-
filtered from a saturated soil paste. Soil extracts were
refrigerated prior to analysis to minimize possible
denitrification.
Collection of Agricultural Data
Agricultural practices data which include the type of crops
grown and the quantities of nitrogen fertilizer applied were
recorded for every tile system investigated during 1966 and
1967. Irrigation application rates and quantities of runoff
were determined for several tile systems from 1.959 to 1963.
Crops^
Cropping data were collected from individual farm operators
and irrigation district offices of the actual crops grown
for any tile system between the years 1959 through 1967.
Irrigation
Actual amounts of applied irrigation water were determined
for a number of tile-drained fields from 1959 to 1963.
38
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Headgate irrigation requirements (quantities of water
required in the production of various crops, exclusive of
precipitation) were used in lieu of actual applied water
data for determining irrigation requirements in major tiled
areas during 19&7 a^d 1968.
Samples of applied water were collected during irrigation to
determine the relative amounts of nitrogen being applied in
the irrigation water. These samples were analyzed for
nitrate, phosphates, and electrical conductivity. Laboratory
results showed very low concentrations of nitrogen in forms
other than nitrates. Nitrate -nitrogen (NC>3-N) in the irriga-
tion waters was found in concentrations of ^ mg/1, which
amounts to about 11 pounds of nitrogen per acre -foot of
water applied .
Phosphate-phosphorous (P(Xt|-P) concentrations in irrigation
water were nearly always less than 0.5 mg/1 . Electrical
conductivity usually ranged from 250 to 350 micromhos.
Irrigation Runoff
Although irrigation runoff was only measured during the
initial investigations, samples were collected to determine
the nitrogen concentration. Nitrogen (NO^-N) averaged about
6 mg/1 for all of the samples collected.
Fertilization
Fertilization has been considered by many to be one of the
most important factors contributing to nutrients in tile
drainage systems. To investigate the quantities of nitrogen
available for leaching and possible accumulation in the
subsurface waters, historic and current fertilization rates
were obtained. These are discussed in this subsection.
Certain aspects of nitrogen gains and losses are also
discussed. However, a nitrogen-balance study was not the
intent of this investigation.
Historical Use of Fertilizers. Commercial nitrogen ferti-
lizer has been used ,in the areas around Gustine, Mendota
and Tulare Lake area for the last 30 years . In the area
from Byron to Gustine, fertilization has been limited by
dairy farming and raising of lima beans, a legume which
does not require fertilization. However, orchards between
Byron and Gustine have been fertilized regularly -with
ammonium-sulfate fertilizer at the rate of 4 to 8 pounds
per tree (about 80 to 100 trees per acre). Although ferti-
lizer use is still somewhat limited by the type of crop
39
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grown in the northern areas, farmers near Tracy apply
nitrogen fertilizer to most truck and field crops at 60 to
100 units per acre, which is very close to that applied in
the central and southern areas.
Application rates of nitrogen fertilizer have generally
increased in the past ten years. The rates for cotton, rice,
barley and safflower have nearly doubled on many farms in
the central area since I960. This has been brought about by
recommendations of farm advisors and consultants for ferti-
lizer companies. Furthermore, an increased usage has also
resulted in some areas from plantings of lettuce, bell
peppers and other such high-fertilizer-use crops.
Types and Methods of Use. Both commercial and natural ferti-
lizers were used in tfre tile-drained areas. The methods of
application depend a great deal on the types being used
which are discussed in the following subsection.
Commercial FgrtilIzers. Various forms of nitrogen
fertilizer are~pbpurar in the study area; ammonium-
sulfate, urea, and aqua-ammonia are the most
popular. Row crops are generally banded with
fertilizer, whereas some field crops, such as
barley and rice, have areal applications. Urea
fertilizer is used almost exclusively to reduce
denitrificatlon losses in rice crops.
Phosphate fertilizers have been used to a limited
extent on the west side; however, regular applica-
tions are made to large acreages of soil in the
Tulare Lake area.
Animal and Green Manures. The amounts of nitrogen
added from animal manure and green manure (cover
crops) were not determined because these materials
contain minimal amounts of nitrogen. Average farm
manure generally contains less than 0.5 percent
nitrogen by weight, and the amounts provided by
green manure crops are extremely variable (12).
No attempt was made to determine the amounts of
nitrogen contributed by legume crops such as
alfalfa or beans. The amount of atmospheric
nitrogen "fixed" by legumes is quite variable;
also, the amount of nitrogen added to the soil
after several years growth of a leguminous crop is
questionable (13).
Volat i1i z at ion. Volatilization losses after fertilization
can be high under certain conditions (1^4). However, for
40
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this investigation, volatilization losses were considered
more than offset by the quantities of nitrogen added in
irrigation water.
Data Sources. Records of commercial fertilizer applications
were collected along with the cropping data. Estimates of
missing or inadequate data for a given crop were based on
fertilizer recommendations of farm advisors or local ferti-
lizer companies for a particular year.
Investigations of Native Nitrogen
In addition to routine monitoring of tile drainage systems,
indigenous nitrogen in soil profiles was investigated in the
field. A literature review concerning residual nitrogen in
parent materials was also performed.
Soil Profile Nitrogen Sampling
Forty-five soil profiles representing different physiographic
positions and soil series were sampled for indigenous
nitrogen along the west side. Virgin sites were sought to
obtain the quantity of nitrogen in the soil before irriga-
tion. Several dry-farmed and irrigated sites were also
sampled. All profiles were logged for soils occupying recent
alluvial fan, older alluvial fan, basin rim, and basin
physiographic positions. Sites were hand-augered to a depth
of 10 feet or more and samples were collected at 1-1/2-foot
increments for nitrogen analyses.
Parent Material Nitrogen Sampling
Data on residual nitrogen concentrations of parent materials*
were obtained from Investigations (15) conducted in 1959
along with deep boring investigations, to determine sources
of high nitrates observed in shallow ground water on the
east and west sides of the Valley. Alluvial parent sources
(cretaceous marine sediments of the Diablo Range) in
selected drainage ways (Arroyo Hondo and Arroyo Ciervo) were
sampled, Including an array of different materials, such as
zones within the stratum, mudflows, cross sections of
arroyos, mud puddles, and streams.
*Prov 1 cied"by The Agricultural Research Service.
41
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SECTION V
RESULTS AND DISCUSSION
This section discusses the average nutrient concentrations
and discharges from tile drainage systems monitored. Empha-
sis is placed on long-term and short-term nutrient varia-
bility, seasonal and areal variability, and variability due
to agricultural practices, physiography, and soils.
Indigenous nitrogen in virgin soils, irrigated soils, and
parent materials is also discussed.
Average Nutrient Concentrations
The grand average concentration of nitrogen (nitrate-
nitrogen) in composited drainage discharged from all systems
intensively investigated throughout the entire period of
study was 19-3 mg/1. This concentration is very close to
the 21 mg/1 value predicted in Bulletin No. 127 (l) by the
Department of Water Resources.
Eighteen "satellite" systems, selected at random within the
major tiled areas, were monitored to obtain "back-up" data
and to determine the feasibility of monthly sampling. The
composited drainage (individual nitrogen concentrations
weighted by tile flow) averaged 23.6 mg/1 for an eight-month
period.
The composited drainage for all the tile systems monitored
regularly in the major tiled areas, the isolated stations
outside the areas, and the "satellite" stations averaged
20.0 mg/1 nitrogen.
The average concentration of phosphorus (orthophosphate) in
drainage composited from the intensively monitored major
tiled areas averaged 0.09 mg/1, slightly less than the
0.15 mg/1 predicted in Bulletin No. 127.
Average Discharge
Tile drainage discharge averaged 1.4 acre-feet per acre for
the same period of study; total dissolved solids (TDS)
averaged 3,625 mg/1. The 1959-63 values were excluded from
the grand average values given because the nutrient or TDS
constituents could not be weighted by flow. They are
presented in Table 7 for comparison.
-------
TABLE 7
AVERAGE DISCHARGE, NUTRIENT CONCENTRATIONS,
AND TOTAL DISSOLVED SOLIDS FROM SAN JOAQUIN VALLEY TILE DRAINAGE SYSTEMS
Annual Averages 1 Weighted)
Parameters :DWR (Bull. 1,27) :UCLA:DWR Nutrient Investlg. : Grand
: igSg-bSJ/ :19b2:19bb 19b7 T915B 19&9": Averagel'
Discharge (ac-ft/ac) NR 0.72 1.5 1.3 1.4 1.4 1.4
Nitrogen (N03-N, mg/1) 21.0 25.1 18.6 18.6 19.9 19.4 19.3
Phosphorus (POi,-P, mgA) 0.15 0.08 NR 0.12 0.10 0.05 0.09
Total Dissolved Solids (mg/l) 6,500 NR 4,550 3,100 3,200 3,550 3,625
Number of Systems Sampled 29 4 7 4o 42 20
I/ Values are arithmetical averages.
?/ Weighted average based on flow.
NR = No record.
Variability of Nutrient Concentrations
Tile Discharger with Time
Long-term and short-term variabilities of average nutrient
and TDS concentrations and discharges are discussed in this
subsection.
Long-term Nitrogen Variability
Long-term variability deals with the changes in average
discharge observed from the study area over several years
and the related changes of nutrient concentrations that take
place in the composited drainage. Variability of nitrogen
in individual tile systems is also compared.
Composited Drainage. Although the figures in Table 7
represent the weighted average values for the different
periods of study, some variability exists between years.
The differences in discharges and tile drain constituents
between years are small, considering the number of tile
systems sampled and the geographical areas represented for
any given period. For instance, in 1962 the highest average
nitrogen concentration (25.1 mg/l) occurred in the composited
drainage from four tile systems within the Gustine-Mendota
area. In 29 systems sampled in 1959-63, most of which were
situated in the same area, the concentration was only
M.I mg/1 less.
-------
Closer correlations between annual nitrogen concentrations
occurred during the more Intensive investigations conducted
from 1966 to 1969. Average nitrogen concentrations for 1966
and 1967 were identical. However, the data for 1966 were
based on just seven tile systems in the central area, whereas
the data for 196? were based on forty systems located through-
out the San Joaquin Valley.
The small difference between 196? and 1968 may have occurred
because only seven months' data were obtained in the
northern area during 196? and the acreage sampled was
slightly less. The 1969 value of 19.4 mg/1, which also
compares favorably, is based on a monthly sampling frequency
of fewer than half the systems sampled in 1968.
Average discharge (based on the total acre-feet discharged
per estimated areal tiled acres) was nearly the same for all
years, except during the studies conducted by the University
of California, Los Angeles, when only four tile systems were
investigated.
Phosphorous concentrations in composited drainage were
nearly the same for 1967 and 1968 but were much lower in
1969, when the Tulare Lake area could not be sampled because
it was flooded. Although phosphorous concentrations appear
to change little from year to year, the percent of change is
higher for phosphorus than it is for nitrogen.
The high TDS value for 1959-63 is based on "salt routing"
investigations conducted by the Department of Water Resources
(l). The average value (flow-weighted) of 4,550 mg/1 was
determined from seven systems in the Gustine-Mendota area.
This is a significantly higher value than the values obtained
for 1967 and 1968.
Individual Systems. Although average nitrogen concentrations
changed little from year to year in drainage composited from
the study area, leaching and fertilization were thought to
affect the nitrogen concentrations in individual systems on
a long-term basis. Therefore, in an attempt to evaluate the
possible long-term variability of nitrogen, all historic
sampling records available for Individual tile systems were
analyzed. Twelve tile systems were selected for which
records showed occasional sampling prior to 1966. These
data are presented in Table 8. Data for individual stations
from 1966 to 1969 are based on weekly samples collected over
a full year and monthly samples collected in 1969.
Flow values in gallons per minute (GPM) and concentrations
of total dissolved solids (TDS) are shown for comparative
purposes. The values given for flows represent the average
-------
TABLE 8
NUTRIENTS, TOTAL DISSOLVED SOLIDS AND
FLOWS FROM INDIVIDUAL TILE DRAINS BY YEAR
Tile ;
System j
BAY 0711
CLG 7551
CLC 7651
DPS 4616
BFS 8003
BFS 7402
FBH 8061
BFS 6001
FBH 5056
FBH 2016
ERR 6705
CCN 3550
Drain
Constituents
and Flows
N03-N (mg/1)
TDS (mg/1)
Flow (GPM)
NO-j-N (mg/1)
TDS (mg/1)
Flow (GPM)
NOj-N (mg/1)
TDS (mg/1)
Flow (GPM)
NOj-N (mg/1)
TDS (mg/1)
Flow (GPM)
NOj-N (mg/1)
TDS (mg/1)
Flow (GPM)
NO,-N (mg/1)
TDS (mg/1)
Flow (GPM)
NOj-N (mg/1)
TDS (mg/1)
Flow (GPM)
NOj-N (mg/1)
TDS (mg/1)
Flow (GPM)
N03-N(mg/l)
TDS (mg/1)
Flow (GPM)
NOj-N (mg/1)
TDS (mg/1)
Flow (GPM)
NO^-N (mg/1)
TDS (mg/1)
Flow (CPM)
MOj-N (mg/1)
TDS (mg/1)
Flow (GPM)
: . Year
i 1959^X i 196l2/ ; i962i/ \ iy&3l/ :
3.0 2.0
2,590 2,756
41 12
3.4
2,510
150
4.3 2.4
2,910 2,357
183 56
2.1 1.3
12,800 12,600
130 7.0
6.6
14,300
15
8.5
3,776
171
7.9 3.6
8,120 8,360
162 68
10.0
3,100
87
61.3 36.8 37.2 51
9,720 6,700 7,586 9,480
42 84 79 10.0
10.4
6,885
16
12.4
3.H87
63
5.4
2,627
136
19663/ ! 19671/ \
7.9
5,000
3
6.5
2,786
179
9.6
2,700
161
5-2
6,867
69
6.4
10,300
36
13.4 11.1
4,403 3,700
409 211
5-6
3,870
81
11.2 18.2
3,976
457 120
50.0 37.1
6,200 5,000
31 129
6.6
4,300
39
15.9
3,600
111
8.4
2,300
182
: 19683/
7."
4,100
5
8.2
2,975
187
11.4
2,940
196
3.7
4,000
130
6.7
8,400
97
10.0
3,640
482
4.8
3,720
190
. 13.3
2,850
260
49.4
6,550
63
5.1
2,100
124
13.7
3,675
50
6.7
2,260
•118
! 1969V
11 .2
2,583
341
11.3
2,670
92
9-0
9,515
130
5.1
7,555
77
15.7
4,810
5212/
8.05/
2,91oi/
53.7
6,280
53
9.3
4,750
79
I/ Values represent one to three samples collected at each station.
2/ Values represent one to fifteen samples collected at each station.
3/ Values represent weekly samples for a full year.
4_/ Values represent monthly samples for a full year.
5_/ Values represent only one sample.
46
-------
flows of only a few measurements at different times of the
year prior to 1966. Time-weighted average flows were
computed from data obtained during the more intensified
studies. Average TDS concentrations were determined from
available mineral data prior to 1963 and flow-weighted from
electrical conductivity values thereafter.
The data show evident variability of nitrogen concentrations
in drainage between years for nearly all the systems. The
changes in nitrogen concentrations can possibly be explained
in that many of these stations were sampled at different
times of the year and are represented by changes in agricul-
tural practices (i.e., crops and irrigation).
By making comparisons of two distant periods of most complete
data (1961 and 1968), the following observations were made:
1. Nitrogen concentrations increased in ten out of eleven
systems over a seven-year period.
2. TDS concentrations decreased in seven out of eleven
systems for the same period.
3. Nearly as many tile systems decreased in flow as
increased.
Increases of nitrogen were also noticed during the periods
of more intensive sampling (196? through 1969 inclusive).
Six out of eight systems showed increases in nitrogen concen-
trations and, again, these increases were not particularly
related to changes in flow or concentrations of TDS.
Although limited data were available for the earlier years
and nitrogen concentrations varied greatly between years for
some of the drains studied, two facts remain clear:
(l) there is no apparent trend that might indicate leaching
or an accumulation of nitrogen in the soil over long periods,
and (2) tile systems having rather high initial nitrogen
concentrations remain rather high.
Short-term Nitrogen Variability
Nitrogen and phosphorous concentrations in drainage from all
systems investigated varied according to the season.
Frequent irrigation tended to lower the nutrient concentra-
tions in most of systems monitored, and highly erratic varia-
tions of nutrient concentrations were observed during
irrigation of many systems . Nitrogen concentrations as
observed in the field and from graphical analyses of individ-
ual systems would increase, decrease, or remain about the
same during irrigation at a particular site. No matter what
-------
the response, when irrigation ended, nutrient concentrations
nearly always tended to return to the levels observed prior
to the beginning of the irrigation season.
Nutrient, TDS, and flow variabilities were investigated hourly
and daily for several tile systems. As part of the analysis,
monthly variability of flows and nutrients was determined
for every system studied.
Hourly. Nitrogen concentrations were first observed to vary
in drainage from individual systems where frequent samples
were collected for treatment studies (Interagency Agricul-
tural Wastewater Treatment Center at Firebaugh, California).
Investigations were later conducted at four sites to deter-
mine the actual nitrogen variation that occurs in drainage
from one hour to the next and to aid in determining a proper
sampling frequency.
Sampling was scheduled to coincide with periods of irriga-
tion to make the most of possible nitrogen variations and to
determine the possible effects of dilution. Samples were
collected and analyzed by routine methods set up for the
monitoring program. Results of the hourly investigations
appear in Table 9; variable phosphorous concentrations,
electrical conductivity values, and flows are compared.
TABLE 9
HOURLY VARIATION OF FLOWS, NUTRIENTS AND ELECTRICAL
CONDUCTIVITY IN DRAINAGE FROM FOUR TILE DRAINAGE SYSTEMS
System
Flows
Nutrients
(8Pm)
Max. :Min.: Mean
Std.
Dev.
NOvN, n»8/l
: : : Std.
Max.:Min.: Mean: Dev.
Max
: Electrical
POU-P, mg/1
:Min.:Mean:
Std.
Dev.
;
:Max.
(E.G.
: Min.
Conductivity
x 10-°)
:Std.
: Mean :Dev.
UID 2133 382 382 382 0 12 k 8.0 1.830.750.130.560.16 3,0002,900 2,950 29
BFS 71*02 59l» 561 571 10.2 1*9 2U 1*0.2 6.24 0.26 0.06 0.16 .051 1*,600 U,200 k,kOO (f)
FBH 3236 191* 131* 15619.3185 92 166.019.8 0.1*50.150.21* .07312,0009,1*0011,230716
CCN 3550 273 193 22U 22.2 1*9 18 30.0 6.1*7 1.60 0.75 1.16 0.19 3,0002,200 2,61*2239
A mean nitrogen value was determined for weekly samples
collected one month before and one month after the 24-hour
studies. The mean weekly values compared well with mean
hourly values of the same systems in three cases (Table 10).
Daity. At the beginning of the intensive monitoring investi-
gations, samples were collected at close intervals (three to
four days), and daily in some instances, until an appropriate
48
-------
TABLE 10
HOURLY VS. WEEKLY MTTROCffiN CONCENTRATIONS
: Nitrate-Nitrocen (nur/l) _ ,
System :
;
UID 2133
EPS 7402
FBH 3236
CCN 3550
I/ Two -month p
Weekly!/
Range :
8- 39
24- 59
82-230
18- 46
eriod.
:
Mean :
19
38
144
30
Hourly^
Range :
4- 12
24- 49
92-185
18- 45
Mean
8
ko
166
30
Twenty- four hour period.
sampling frequency could be established. In samples
collected dally, nitrogen concentrations varied slightly
from day to day but tended to remain generally constant,
unless the field in question was being irrigated. Intensive
irrigations effectively reduced the nitrogen for short
periods in many cases. The longest period of consecutive
sampling covered five days at one station. Nitrogen concen-
trations in the drainage ranged from 30.5 to 45.1 mg/1 . The
mean value was 35.5 mg/1* with a standard deviation of
6.3 mg/1 (18 percent).
Samples collected at three-to-four-day intervals showed a
greater variation than those collected daily. In a random
example which was sampled 11 times during the month, the
standard deviation was 9.7 mg/1, or 30 percent of the mean
concentration of 30.6 mg/1. Similar variations were
observed in the data collected from the other systems
sampled at three- and four-day intervals during a period of
irrigation.
The foregoing data led to the decision that weekly sampling
was adequate for the investigation. This determination was
based on the following findings: (1) mean hourly nitrogen
concentrations show a correlation to mean weekly values over
a two-month period; (2) large variations in nitrogen due to
the immediate effects of irrigation usually occur rapidly
and tend to return to the original concentration after irri-
gation; (3) because irrigation is generally repeated every
10 to 15 days for most crops, weekly samples tend to show
nutrient levels before, after, and during irrigation; and
-------
changes in flow and resulting changes in nutrient
concentrations due to irrigation are not always abrupt
because of the number of days required to irrigate a given
field.
Monthly Variations in Individual Systems. Monthly varia-
tions of nutrient concentrations were observed in every tile
system investigated. The direction, magnitude, and
frequency of nutrient variability differed between tile
systems and seemed to depend mainly upon irrigation manage-
ment and field location. Many tile drain flows fluctuated
widely, which grossly affected the nutrient concentrations;
others had sustained flows (flooded conditions) that caused
a prolonged reduction in the nutrient concentrations.
The many variable conditions affecting flows and nutrient
concentrations meant that results for an individual system
cannot be considered typical of a given number of tile
systems or representative of a large area. However,
examples presented in Figures 10 and 11 do serve to illus-
trate the monthly and seasonal variability of tile discharge,
nutrients and TDS concentrations in individual systems where
irrigation practices differ.
Monthly Variations in Composited Drainage. Monthly varla-
tion's of nutrients in the drainage composited from the
entire study area show a definite trend in relation to the
seasons.
Nutrient concentrations in drainage varied greatly between
individual tile systems in the study area and appeared to
decline in many tile systems during the summer months. In
drainage composited from the entire Valley, nutrient concen-
trations declined appreciably during the peak irrigation
season. The magnitude of seasonal variability is illustrated
in Figure 12. Nutrient and TDS concentrations are flow-
weighted monthly averages based on a two-year period of
study (1967-68). Figure 12 shows that concentrations of
nitrogen, phosphorus and total dissolved solids varied
monthly and inversely with the tile discharge. Twofold
variations of both nitrogen and phosphorus were apparent in
the drainage from winter to summer. The highest concentra-
tion of total dissolved solids occurred in April and the
lowest in August. The average TDS varied about 1,000 mg/1
from spring to summer, a change that was not as spectacular
as the changes in the nutrients.
A fourfold increase was noted in the average discharge from
winter to summer.
50
-------
JAN FEB MAR APR MAY JUNJULAUGSEPOCT NOVDEC
1968
FIGURE 10-VARIABILITY OF FLOW, NUTRIENTS, AND TOTAL DISSOLVED SOLIDS FROM A
FLOODED TILE DRAINAGE SYSTEM
^ ~f|'-|]
,0 I
60OO
•4500
•3OOO
•I50O
.V,
DEC
FEB MAR APR MAY JUN JUL AUG SEP OCT NOV
1968
FIGURE II • VARIABILITY OF FLOW, NUTRIENTS. AND TOTAL DISSOLVED SOLIDS
FROM A PERIODICALLY IRRIGATED TILE DRAINAGE SYSTEM
Areal Variability
Nutrient concentrations and flows were found to vary
according 'to the location of individual systems and also in
drainage composited according to major tiled areas.
Individual Systems
Reconnaissance investigations conducted in 1966 led to the
discovery of wide differences in flows and nutrient
-------
concentrations between
tile drainage systems
within major tiled
areas and between
major tiled areas.
Nitrogen concentra-
tions ranged from 2 to
400 mg/1 in drainage
collected from individ-
ual tile systems over
the entire area; phos-
phorous concentrations
ranged from 0.01 to
6.6 mg/1. Tile flows
ranged from no flow to
more than 1,600 gallons
per minute during
summer months. Samples
collected from individ-
ual systems ranged in
TDS from 1,320 to
14,630 mg/1 in a given
month. Most systems in
the central area
discharged effluent with TDS concentrations exceeding
3,500 mg/1. Several samples collected from an experimental
tile system in the San Luis Unit Service Area exceeded
100,000 mg/1 at low flow.
AN FEB MAR APR MAY
AUC SEP OCT
250O
NOV DEC
L
JUN JUC
1967- 68
FIGURE. 12- SEASONAL VARIATIONS OF DISCHARGE,
NUTRIENT CONCENTRATIONS, AND TOTAL DISSOLVED SOLIDS
Composited Drainage
The variability of discharge, nutrients, and TDS in compos-
ited drainage from major tiled areas was much less than that
observed in individual systems.
Tile Drain Discharge. Discharges varied between major areas,
The highest discharges were noted in the Byron-Westley area,
which for the 1967-68 period averaged 2.3 acre-feet per year
(Table 11). This amounts to more than twice that of the
Gustine-Mendota area, which had the next highest quantity of
discharge.
Nitrogen. Nitrogen content in the composited drainage from
the central area averaged three times more than in drainage
from any other major tiled areas. The average nitrogen
value was 32.8 mg/1. (A value of 21 mg/1 had been predicted
for the entire Valley.) The higher nitrogen concentrations
in the tile discharge from the central area greatly
influenced the overall nitrogen concentration in the compos-
ited drainage of the Valley. However, the low nitrogen
52
-------
TABLE 11
AVERAGE DISCHARGE, NUTRIENT CONCENTRATIONS,
AND TOTAL DISSOLVED SOLIDS BY MAJOR TILED AREAS
1967 AND 1968
:Nitrate-:Phosphate-:Total
. , „. , N:Nitrogen:Phosphorus: Dissolved
.(ac-ft/ac). (nig/l) : (mg/1). :Solids (mg/1)
Major Tiled
Areas
'Discharge
By r on -We s 1 1 ey
Westley-Gustine
Gustine-Mendota
Tulare Lake
2.3
0.69
1.12
0.57
8.5
9.0
32.8
9.6
0.09
0.06
0.07
0.69
2,170
2,7^0
4,130
3,760
content of drainage from systems in the northern and
southern areas tends to dilute the high nitrogen level that
might otherwise occur in drainage from the entire study area,
Phosphorus, In drainage composited by different areas,
phosphorus was found in much lower concentrations than was
nitrogen. The highest concentrations were observed in
drainage from the southern area (Tulare Lake). Phosphorous
concentrations there averaged O.b9 mg/1, about seven times
higher than any other area.
Total Dissolved Solids. Drainage from the Gustine-Mendota
area was the highest 3Tn TDS concentrations. TDS concentra-
tions in the composited drainage from the Byron-Westley and
Westley-Gustine areas were about 1,000 mg/1 lower than the
drainage from the other two areas. The difference in the
average TDS in drainage between the Gustine-Mendota and
Tulare Lake areas was small.
Variability Due to Agricultural Practices
Tile drainage flow as well as nutrient concentrations are
generally affected by certain agricultural practices. Irriga-
tion, cropping, and fertilization practices and their effects
upon tile drainage are discussed in this subsection.
Influence of Crops on Tile Discharge
Certain heavily irrigated crops directly influence flows in
tile drainage systems. When irrigated, rice, alfalfa, and
cotton crops produced almost immediate increases in drainage
53
-------
response and, at times,, sustained high flows. Rice, for
example, is flooded from early June through August. Although
other factors such as the amount of vegetative ground cover,
plant conditions, stage of growth, soil 'conditions, and
other factors have been known to affect the amount of
effluent discharged, irrigation intensity was considered the
most important single factor. Table 12 presents the annual
average tile discharge for various crops in 1959-63 and 1967,
Several tile systems are represented for each crop shown.
TABLE 12
COMPARISON OF
TILE DRAIN DISCHARGE BY VARIOUS CROPS
(in acre-feet per acre)
Major Crop :
Rice
Cotton
Alfalfa
Beets
Beans
Pasture
Orchards
Safflower
Barley
Fallow
General Field Crops
Discharge (Acre-Feet per Acre)
1959-t>3
Max.
4.2
1.0
0.2
0.9
--
0.9
--
—
1.3
1.1
0.7
: Mln.
0.5
0.2
0.2
0.7
--
0.7
--
--
0.1
0.3
0.4
: Avg.
1.3
0.5
0.2
0.8
--
0.8
--
--
0.5
0.6
0.5
: 19b7
: Max. :
2.0
3-0
17-3
1.5
2.0
--
0.8
2.0
0.7
--
--
Mln. :
0.7
0.5
0.3
0.1
1.0
—
0.4
0.7
0.3
--
--
Avg.
1.4
1.1
3-1
1.0
1.3
--
0.7
1.4
0.3
--
—
The kind of crop does not always dictate the quantity of
tile drainage. Several other tile systems (not shown in
Table 12) draining diversified row crops within the study
area discharged more per year than did the systems from
tiled rice fields.
Influence of Crops on Nitrogen Concentrations
Rice was the only crop that exerted an appreciable influence
on nitrogen concentrations observed in tile drainage systems
The decreased nitrogen concentrations noted in effluent
-------
discharged from rice fields were possibly due to a combina-
tion of two interrelated factors. Dilution, which is a
physical lowering of nutrient levels resulting from irriga-
tion, and denitrification, which involves nitrogen losses
that are promoted by anaerobic soil conditions, are probably
the main reasons for the low nitrogen levels. In some cases
tile drainage from flooded rice fields in the Gustine-
Mendota area showed mid-summer decreases in nitrogen to less
than one-third their wintertime concentrations. One tiled
field in particular dropped from a January level of 63 mg/1
to 7 mg/1 for the months of May, June, and July.
The average annual nitrogen concentration in the combined
drainage from all rice fields, which for this study was
limited to the Gustine-Mendota area, was 10.9 mg/1. The
average concentration for all other tile-drained crops
investigated in the same area was 43.7 mg/1.
Irrigation Influence on Discharges
The influence of crops upon tile drainage flow without
regard to the quantities of irrigation water applied has
already been discussed in the foregoing subsection. Actual
applied water was determined only for a few tile systems
during the initial investigations. Because of the large
number of tile systems being sampled and the complexity of
irrigation practices on many large tiled fields, measurements
were not made during the more intensive investigations.
However, headgate irrigation requirements (10), the quanti-
ties of water required in the growth of crops exclusive of
rainfall, are very nearly the same for many crops in the
different major tiled areas. The quantity of tile discharge
compared to the irrigation intensity (determined from head-
gate irrigation requirements) within the major tiled areas
is presented in Table 13.
Irrigation Influence on Nitrogen Concentrations
Although the type of crop grown usually determines the
relative amounts of water required, overirrigation and, to
a lesser extent, underirrigation can greatly affect the
quantity and nutrient quality of tile drainage. Low
nutrient concentrations seemed to be associated with flooded
soil conditions; denitrification and dilution were suspected.
Heavy irrigations may also add nitrogen to the soil.
Inclividual Systems. The influence of irrigation upon
nutrient concentrations in individual systems varied greatly.
In many but not. all systems, nitrogen concentrations varied
55
-------
TABLE 13
TILE DRAIN DISCHARGE VS. IRRIGATION
INTENSITY WITHIN MAJOR TILED AREAS
196?
Irrigation
Intensity!/
•
Light (0.0-0.9)
Medium (1.0-2.9)
Heavy (3.0-3-9)
Very Heavy (4.0-8.0)
Flooded
Average
Tile Discharge (ac~
Byron- : Westley-: Gustine-
Westley : Gustine : Mendota
2/
272
2.2
.8
2/
2/
171
.5
2/
2Y
.7
1.1
1.0
.4
.8
ft/ac)
: Tulare
; - Lake
.6
.6
1.2
.5
£/
I/ Arbitrary categories based on headgate irrigation
requirements of crops, weighted by acres.
2/ No tiles within the irrigation intensity categories.
inversely with tile flow. Several tile systems located in
the northern area had nutrient concentrations that remained
rather constant throughout the study period. However,
nitrogen was observed to increase with increases in tile
discharge from several individual tile systems within the
study area,
Den it ri f i cat ion. The variability of nitrogen in drainage
from certain tile systems may have been due to denitrifica-
tion which has already been mentioned in regard to crops
that were flooded. However, low nitrogen concentrations
were found in drainage from tiled areas that were not
flooded. Although investigations were not conducted to
determine if the seasonal decrease in nitrogen concentra-
tions was actually due to denitrification, findings by other
investigators show that under certain conditions denitrifica-
tion does take place. Ponnamperuma (16) reports that no
more than 3 mgA nitrate had ever been reported in the soil
solution of a flooded soil following irrigation and that
nitrogen losses are due chiefly to the reduction of nitrate
to the oxides of nitrogen or nitrogen gas. Ponnamperuma
concludes that nitrate is not a suitable fertilizer for rice
because of denitrification and leaching losses. Power (17)
reports bacterial denitrification losses may account for a
major part of fertilizer nitrogen applied in lands with
poor drainage. Meek, et al (lo), found significant
decreases of nitrogen in saturated fine-textured soils which
were fertilized under a laboratory-controlled environment.
56
-------
Nitrogen losses and the production of nitrogen gas corre-
sponded to increases in soil moisture above Ml percent. He
also found that nitrogen losses in tile drainage from the
field only amounted to 1.5 percent of the 246 pounds per
acre applied. Decreases in nitrate were associated with
increases in depth and proximity of the water table. Inves-
tigations conducted by the then Federal Water Quality Admin-
istration (FWQA) in cooperation with the Department of Water
Resources showed similar denitrification in saturated
Panoche loam and Tulare loam soils of 0.54 percent and
0.62 percent per hour, respectively.
In several tile systems investigated for dissolved oxygen,
the lowest concentrations were observed in drainage from
rice fields. Fields having more than one crop had the
highest levels, followed by fields in which cotton and beans
were grown. Ranges and averages are presented in Table 14.
TABLE 14
DISSOLVED OXYGEN CONCENTRATIONS
IN TILE DRAINAGE FROM VARIOUS CROPS
•
•
Crop :
•
«
Rice
Fallow
Alfalfa
Beans
Cotton
Diversified
Number :
of :
Systems :
3
1
3
4
5
9
-Dissolved
Maximum :
1.8
1.6
3.5
6.0
7.9
7.8
Oxygen
Minimum
.7
1.6
3.2
2.4
1.5
0.9
(ppm)
: Average
1.4
1.6
3.4
4.4
4.9
6.1
Dilution. Dilution was also mentioned as a cause of low
nitrogen in heavily irrigated crops. The decrease in
nitrogen due to dilution is somewhat substantiated in that
nitrogen levels are the lowest during peak irrigation and
nearly always approach the preirrigation concentrations.
Also, TDS levels decreased simultaneously with nitrogen
concentrations in drainage from many Individual systems
where discharges remained high in the summer months.
Figures 10 and 11 illustrate the reactions of TDS to irriga-
tion and their correlations to nutrients. A decrease in
TDS and nutrients (nitrogen and phosphorus) along with an
increase In discharge was observed in the composited
drainage from the entire study area (Figure 12), This
decrease Is presumed to be caused partly by dilution and
57
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partly by denitrification. The mid-summer decline of
nutrients in the composited drainage cannot be attributed
solely to the influence of drainage from rice fields. Similar
decreases in nutrient and TDS concentrations also occurred
in composited drainage from the central area when rice field
data were eliminated.
Nitrogen in Irrigation Water. One important aspect of irri-
gatioh is the amount of nutrients added during application.
Nitrogen in irrigation water is usually found in the nitrate
form; organic nitrogen is nearly always found to be less
than 1 mg/1. The nitrate form of nitrogen is readily suita-
ble for uptake by most plants, although the ammonium ion can
be assimilated by some crops. However, more than an acre-
foot of water is applied to fields for preirrigation, when
no crop is being grown, and during early stages of growth
when the root.development is not great, which could result
in losses to the ground water. Lysimeter studies ('19) have
shown exceptionally high leaching losses when soils are
fallow. Nitrate-nitrogen concentrations in irrigation water
applied to tiled fields in the study area were determined to
be 4.0 mg/1, which amounts to approximately 11 pounds of
nitrogen added for every acre-foot of irrigation water
applied. Nitrogen contributed in this manner could exceed
40 pounds per acre for certain heavily irrigated crops for
even one year, discounting other possible losses.
For this investigation, nitrogen contributed to the soil in
applied water or rainfall was assumed to be about the same
in all areas, considering crop diversification and water
requirements of such large areas.' Gains in nitrogen due to
irrigation application were considered more than "offset" by
the amounts lost due to deep percolation, volatilization,
and denitrification.
Fertilization
Much has been written regarding the leaching of nitrogen
from soils. However, data to show the contribution of ferti-
lizer nitrogen to shallow ground water are scarce. Although
specific studies were not conducted to determine the actual
amounts leaching to the water table, agricultural data
showing the amounts of nitrogen fertilizer applied in" major
tiled areas over a long period are discussed' in relation to
to the concentrations of nitrogen observed in the drainage.
Leaching of fertilizers is also discussed in the subsection
that follows.
Leaching. Lysimeter investigations (19) have shown that the
amount of nitrogen leached through soils during irrigation
58
-------
is quite dependent upon the amount of nitrogen present or
added, its form, the soil texture, the type of crop, and
the maturity of the crop. Dyer, et al (20), showed evidence
of nitrate leaching due to irrigation in comparisons of
irrigated and nonirrigated profiles of Panoche soils on the
west side of the San Joaquin Valley. Johnston, et al (21),
concluded that nitrogen and phosphorous levels in drainage
from west side tile systems correlated with fertilizer appli-
cation. However, as many or possibly even more investiga-
tions have shown that leaching of applied fertilizers is
negligible under certain conditions. Williford and Tucker
(22) reported very low recovery of tagged fertilizer (N^)
in leachate collected from a series of lysimeters filled
with fine-textured west side soils which were cropped,
heavily fertilized, and irrigated routinely. The highest
percentage recovered was in leachate collected from Panoche
fine sandy loam, which was only 3-58 percent of the total
applied. Bower and Wilcox (23) reported that nitrogen
failed to increase in the upper Rio Grande from drainage
influence of three highly fertilized .adjacent areas. In
this case, records of fertilization showed an increase from
a very low to a very high level over a 30-year period. The
absence of nitrates in the drainage was attributed more to
denitrification promoted by anaerobic conditions than to the
possibility of no significant leaching below the root zone.
Applied Nitrogen Versus Discharged Nitrogen. In several
cases,the nitrogen concentrations observed in tile drainage
from individual systems seemed to correlate with the amounts
of fertilizers applied. However, high rates of fertiliza-
tion were recorded for many tiled fields having low levels
of nitrogen in the drainage. Fertilizer records obtained
over a ten-year period are compared in Table 15 to the
average nitrogen concentrations observed in subsurface
waters discharged from major tiled areas. The yield of
nitrogen per acre was also determined for comparison to the
average fertilization rates. For the most part, no direct
correlations could be made during this study between the
quantity of nitrogen fertilizer applied and the concentra-
tions of nutrients in tile drainage. Only in the Gustine-
Mendota area did there appear to be a general relationship
between the two factors. Here the heaviest nitrogen ferti-
lization occurred and the greatest amount of nitrogen was
discharged. However, rather heavy applications of fertilizer
were also, made in the Tulare Lake and Byron-Westley areas for
at least ten years with no appreciable effect on the nitrogen
concentrations observed in the drainage. Also, fertilizer
application for certain individual tiled fields was much
higher than the average fertilization rates indicate; however,
nitrogen concentrations still remained about 10 mg/1. The
59
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relatively low concentrations in the drainage from these
areas show that nitrogen does not accumulate over long
periods in the subsurface waters. The yield of nitrogen
from the Gustine-Mendota area in 196? was nearly as great as
that applied for the same year. Although there was more
yield from this area during 1968, this resulted primarily
from an increase in the total discharge, rather than
increases in the nitrogen concentrations. The data show
that nitrogen concentrations were actually lower for 1968
than 1967. Although fertilizer data were not collected for
1968, it is doubtful that the increase in yield could have
been due to increased fertilization of a large number of the
tile systems in the area.
TABLE 15
APPLIED NITROGEN VS. DISCHARGED
NITROGEN BY MAJOR TILED AREAS
;Quantity of Nitrogen; Average Discharged Nitrogen
Major Tiled : Fertilizer Applied ; 1967 ; 1968
Area :(avg Ibs/acre/year) : Yield : Cone.: Yield : Cone.
;1957-67;1962-6T:1967;(lb8/acre);(mg/l);(lbs/acre);(mg/l)
Byron-Westley
Westley-Gustine
Gustine-Mendota
Tulare Lake
50
33
88
74
61
44
75
68
72
67
92
43
4oi/
14
85
19
7A1/
T.5
34.6
10.5
68
21
112
12
9.2
10.4
31.8
8.7
I/ Partial year's data (seven months).
The yield from the Byron-Westley area increased significantly
in 1968 over 196? because of a longer sampling period.
Phosphorous Fertilization. Phosphate fertilizers were found
fo be applied less frequently than nitrogen fertilizers in
all major tiled areas. Accurate records were not kept on
most farms. Application rates were only obtained from one
large operation in the Tulare Lake area. Records showed
that phosphate fertilizer was applied regularly at the rate
of 50 pounds per acre every other year. Phosphate, concentra-
tions in tile drainage from that area seemed to indicate a
relation between application and discharge. Soil investiga-
tions (24) conducted by the Department of Water Resources
have shown that an association may exist between shell frag-
ments in the soil of the Tulare Lake soil series and the
extraordinary phosphorous content in the tile drainage.
Shell fragments removed from the soil profiles contained
60
-------
0.11 percent phosphorus pentoxide by weight. Laboratory
tests indicate that the shell fragments contained from
0.12 to 0.15 percent phosphate. Also, during the investiga-
tion the odor of hydrogen sulfide gas was detected in
several augered holes where high water table conditions
existed. Anaerobic conditions, indicated by the presence
of the hydrogen sulfide gas, in effect lower the soil pH
which results in acidic conditions within the soil and a
consequent release of phosphates (25).
Variability Due to Physiography
An apparent association between quantity and quality of the
tile drainage and the physiographic positions of the drain
systems led to an investigation of this aspect of tile
drainage. As already pointed out, fertilizer application
rates did not always correlate with the concentrations
observed or pounds of nitrogen discharged in tile drainage.
During the course of the study, it became evident that
certain tile drainage systems occupying alluvial fan posi-
tions discharged effluent containing high concentrations of
nitrogen, whereas systems located in the basin rim and basin
position generally had lower nitrogen concentrations.
Discharge
The highest average discharges were derived from tile
systems located in the older alluvial fan positions.
Several systems in the northern area with exceptionally high
flows were so located. Although these systems discharged
greater quantities of effluent than did tile drains located
in other major tiled areas, they were typical of other
drains not being sampled in that area. Several individual
drains located on older alluvial fans of the central area
also had high discharges.
Nutrients and Total Dissolved Solids
The composited drainage from tile systems within basin and
basin rim positions was significantly lower in nitrogen
than that from alluvial fans.
Phosphorus was six times more concentrated in the drainage
from tile systems occupying basin positions than other
positions.
Composited drainage from tiles located in the basin rim
position was the highest in TDS, followed by the basin
position.
61
-------
The weighted average flow., nutrient concentrations, and TDS
in composited drainage from the systems monitored in the
entire area over a two-year period (1967-68) are summarized
by physiographic positions in Table 16.
TABLE 16
TILE DRAIN DISCHARGE, NUTRIENT CONCENTRATIONS,
AND TOTAL DISSOLVED SOLIDS SUMMARIZED
BY PHYSIOGRAPHIC POSITIONS
1967-68
Physiographic
Positions
Weighted Average Values
Plow : NC>3^N : POij-P : TDS
(ac-ft/ac) ; (nigA) : (mg/1) ; (mg/l)
Recent
Alluvial
Fan
Older
Alluvial
Fan
Basin
Rim
Basin
Weighted
Summation
1.1
1.8
1.2
0.7
1.3
26
15
11
10
19
0.09
0.08
0.09
0.60
0.13
3,160
2,500
4,410
3,450
3,160
Variability Due to Soils
Differences between nutrient concentrations and quantities
discharged were recognized in tile drains from similar
physiographic positions. These inconsistencies led to an
examination of soil series as a criterion for determining
quantity and quality of tile drainage (Table 17).
Discharge
The highest quantity discharged was from one system located
in Ambrose soil series. Drainage from this system exceeded
17 acre-feet per acre per year in 1968. The next highest
discharge was from a tile system located in the Rincon soil
62
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TABLE 17
AVERAGE TILE DRAIN DISCHARGE, NUTRIENT CONCENTRATIONS,
AND TOTAL DISSOLVED SOLIDS FROM DIFFERENT SOIL SERIES
AND PHYSIOGRAPHIC POSITIONS
Physio-
graphic
Position
Recent
Alluvial
Fan
Older
Alluvial
Fan
Basin
Rim
Basin
: : Number
. Soil . f
* Series • °r
: : Systems
Panoche
Sorrento
Panhill
Foster
Rincon
Ambrose
Lost Hills
Oxalis
Lethent
Willows
Tulare
Sacramento
Hacienda
8
6
4
1
4
3
3
4
2
1
k
1
1
:_ . . . rDischarge
.Estimated. fac.f*/
'm Acres * / \
2,071
2,356
595
73
895
169
858
825
390
140
1,080
73
120
0.8
1.9
2.3
0.9
2.0
6.9
1.1
1.9
l.l
1.0
0.5
2.1
1.1
:H03-N 'POU-P I TDS.i/
;(mg/l);(mg/l); (mg/l)
* • «
38
11
45
16
8
7
5U
10
20
1*
7
5
15
0.08
0.08
0.05
0.82
0.08
0.08
0.07
0.08
0.05
0.08
0.63
0.26
0.88
3,720
2,U6o
3,880
2,070
2,290
3,580
U,U70
4,960
5,430
5,640
2,030
3,700
I/ Total Dissolved Solids
series. The total discharge from this system was in excess
of 8.0 acre-feet per acre for 1968. Drainage from these and
a few other tile drainage systems in the study area represents
systems where more water was discharged than applied during
the irrigation season.
Movement of subsurface water into tile systems from outside
influences (lateral movement from other irrigated areas,
canals, and other sources of water) was suspected in many
tile drains when discharges continued after irrigation had
ceased. Although lateral movement was apparent in several
tile drainage systems throughout the study area, none were as
obvious as the two just mentioned.
Tile drainage discharge expressed as acre-feet per acre
depends entirely upon one's interpretation of the acreage
63
-------
actually drained. Contributions of subsurface drainage from
outside influence were impossible to quantify. Therefore,
any attempt to use the foregoing data to predict drainage
from a small area would be erroneous. However, discharges
representing several tile systems within a given soil series
(Table 1?) might be used for predicting drainage from an
extensive area where soil conditions are similar. For
instance, tile systems in the Tulare Lake area discharge low
volumes of effluent. Further installations in this area can
reasonably be expected to do the same. Accordingly, other
discharge values given for specific soils under similar soil
conditions might be applicable.
Nutrients
When drainage from tile systems occupying similar soil series
and physiographic positions was composited, the highest
nitrogen concentration was shown to occur in the drainage
from the Lost Hills soil series (older alluvial fan).
Drainage from related Panoche and Panhill soils (recent fans)
was the next highest in nitrogen concentration. These three
soils represent large alluvial fans along the west side from
Mendota to south of Bakersfield. Tile drainage from tile
systems located in Sorrento and Rincon soils was found to be
low in nitrogen. These soils also represent substantial
acreages of recent and older alluvial fans, respectively,
within the northern area.
Drainage composited from tile systems situated in Oxalis and
Tulare soils, which comprise the largest acreage of the basin
rim and basin positions, respectively, was rather low in
nitrogen. The lowest nitrogen level (4.0 mg/l) was found in
drainage from a single tile system in the Willows soil
series.
Relatively high concentrations of phosphorus were observed
in the drainage from all of the soil series near Tulare Lake.
Foster and Hacienda were slightly higher in phosphorus than
was the Tulare series.
From these comparisons, high nitrogen concentrations in
drainage composited from San Joaquin Valley tile systems were
found to be associated mainly with Panoche and related soil
series located in the Gustine-Mendota area. Tile drains in
this area are expected to contribute approximately 36 percent
of the total drainage from the Valley by the year 2020, and
because nitrogen concentrations are significantly higher in
the drainage from this area compared to other major tiled
areas, the seasonal impact upon a drainage facility becomes
important.
64
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' PANOCHE CROUP
•-BASIN GROUP
SORRENTO GROUP
JAN FES MAR APR MAY JUN JUL AuG SEP OCI NOV 0 C
1967- 68
FIGURE 13-SEASONAL VARIATION OF NITROGEN CONCENTRATIONS
IN DIFFERENT GROUPINGS OF SOILS
Figure 13 compares the monthly average nitrogen concentra-
tions in drainage composited from three groups of soil
series: the Panoche group (Panoche, Panhill and Lost Hills);
the Sorrento group (Sorrento, Rincon, and Ambrose); and the
Basin group (Oxalis, Lethent, and Tulare). The Panoche
group occurs in the Gustine-Mendota area, and the Sorrento
group occurs in the Byron-
Westley area. The Basin
group, which is not a
family grouping, represents
the composited drainage
from basin and basin rim
soil series within all the
major tiled areas. It is
shown to illustrate the
seasonal variation in
drainage having low
nitrogen concentrations
and for comparison to the
family groups. Although
the Panoche and Sorrento
family groups are similar
in texture, soil develop-
ment, and other factors,
they do differ genetically.
The greatest seasonal vari-
ation of nitrogen occurred
in the drainage from the
Panoche grouping. , .
C.3 Jr *—» 0 cnoorwrn GROUP—J-v
The yield of nitrogen
(pounds per acre per month)
from tile systems within
the soil groupings is
presented in Figure 14.
The greatest nitrogen
yield occurred in drainage composited from the Panoche group;
peak yield occurred in March, which was possibly the result
of early leaching during preirrigation. The influence of
relatively high discharge along with low nitrogen concentra-
tions is shown in the contrasting yield of nitrogen between
the Sorrento group and that of the Basin group. Several
tile systems having the highest discharges were associated
with the Sorrento and related soils.
20
I
- 12-
-PANOCHE GROUP
GROUP
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
1967 - 66
FIGURE 14-SEASONAL DISTRIBUTION OF NITROGEN YIELD
IN DIFFERENT GROUPINGS OF SOILS
Total Dissolved Solids
Table 1? also shows that average concentrations of total
dissolved solids were the highest in drainage from tile
systems in the Tulare (basin position) and Willows (basin
rim position) soil series, which are among the lowest in
nitrogen.
-------
Drainage Site Classes
To determine reasonable permeabilities for different soils,
the Department of Water Resources mapped west side soils and
classified them by drainage site classes. This classifica-
tion scheme was based on the physiographic positions defined
earliert on soil profile texture, and on stratigraphy.
These drainage classes permit more exact descriptions of the
ability of a given soil to transmit water both vertically
and horizontally.
Drainage from tile systems within each drainage site class
was composited and averaged to determine the relative
discharge and nutrients for a particular grouping. A map
designating the locations of some of the drainage site
classes mapped along the west side is ^hown in Figure 15.
Meanings of symbols used in the delineations are presented
in Table 18. The acreage of tile systems sampled within
each class is presented in Table 19 along with the average
discharge and concentrations of nitrogen, phosphorus, and
total dissolved solids. The drainage site classes are
presented in their order of decreasing permeability.
? ;-•
FIGURE I5/DRA!~NAGE
CLASSES-GUST!TO MENDOT AREA/
66
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TABLE 18
MEANINGS OP MAP SYMBOLS USED FOR
DESIGNATING DRAINAGE SITE CLASSES
NUMBERS
(Physiographic Positions)
LETTERS
(Soil Permeability Profile Groups)
1 - Alluvial fans on the west
side of the Valley, chiefly
from sedimentary sources.
A - Moderate to rapid permeability
throughout without a significant
restricting horizon.
2 - Basin rim west of the trough.
Alluvium from sedimentary
sources.
3~- Overflow deposits of coarse
and medium texture, adjacent
major channels in the valley
trough.
B - Moderate to rapid permeability to depths
ranging from 8 to 15 feet underlain by
a very slowly permeable horizon beneath
which may be strata of varying
permeabilities.
C - Domlnantly fine-textured surface profile
or one having moderate development,
underlain by stratified alluvium with
combinations of slowly permeable horizons
and moderately to rapidly permeable
strata which will allow relatively free
lateral movement of significant volumes
of water.
- Trough and basin areas which
are the lowest positions in
the Valley.
D - Fine-textured, slowly permeable surface
material, varying from approximately
4 to 8 feet in depth, underlain by thick;
strata of moderately to rapidly permeable
alluvium, often deep deposits of loose
channel sand.
5 - Basin rim east of trough.
Alluvium chiefly from
granitic sources.
E - Strongly developed (claypan and hardpan)
soils or those having a slowly permeable
unrelated substratum (the claypan,
hardpan, or substratum within 60 inches
of the surface), underlain by a combina-
tion of slowly permeable horizons anrt
moderately to rapidly permeable strata.
7 - Low anticlinal ridges.
F - Mainly fine-textured alluvium with
tendency toward increasing density and
degree of compaction with depth. May
include some thick strata of rapid to
moderate permeability which do not
provide space for a significant volume
of water, and often pinch out within the
body of fine material.
I/ Does not occur in the Drainage Site Cla5ses in Figure 15.
67
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TABLE 19
AVERAGE TILE DRAIN DISCHARGE, NUTRIENT
CONCENTRATIONS AND TOTAL DISSOLVED SOLIDS ACCORDING
TO DRAINAGE SITE CLASSES
1968
Drainage:l$umber:Estimated:Dis change :Nutr1pnts
Site : of : Tiled : (ac-ft/:^-^
Class :Drains: Acreage ; ac/yr) : N03-N : ru^-r
IB
6B
1C
2C
4C
4D
5D
IP
2P
2
1
23
5
5
1
1
2
2
870
73
4,883
1,528
1,213
209
60
588
221
0.84
0.87
1.66
1.44
0.56
0.98
0.32
1.68
1.80
32.7
15.8
24.9
10.8
7.7
11.1
5.2
9.3
5.1
0.05
0.82
0.07
0.07
0.59
0.05
2.01
0.05
0.07
5,080
2,070
3,220
3,390
3,290
1,860
7,280
2,890
3,060
The highest discharge according to drainage site classes
occurred in the IF and 2F classes, which according to the
classification are fine-textured alluvium with dense compact
subsoils. These soils which by definition are supposed to
be slowly permeable are greatly influenced by surrounding
high water table conditions. They are represented by two
tile systems in each class. The next highest average
discharge came from drains located in the 1C and 2C classifi-
cations, which are located in alluvial and basin rim soils
with stratified profiles that allow free lateral movement of
water. These last two categories are among the few that are
well represented by tiled acreage. The drainage from these
classes is considered to be more in line with the quantities
expected from highly permeable soils having few restrictions
in the subsoil.
Nutrient concentrations were the highest in drainage compos-
ited from the IB and 1C classifications, which represented
most of the tiled alluvial soils within the study area, and
phosphorus was the highest in the 5D class.
This system of classification, along with additional field
exploration, further correlation to tile discharges and
nutrient concentrations, could possibly be used to project
discharges and nutrient concentrations from areas that are
to be tile-drained in the future.
68
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Residual Nitrogen in West Side Soils
Background
The presence of nitrogen was investigated in various soil
profiles along the west side of the San Joaquin Valley floor,
and these findings correlated rather well with concentra-
tions of nitrogen observed in tile drainage discharge of
similar soils. The following points were the basis of such
correlation.
1. Nitrogen concentrations in tile drainage from alluvial
soils were higher than in drainage from other physio-
graphic positions investigated; in many cases, nitrogen
yields exceeded fertilizer applications.
2. Findings by other investigators presented strong
evidence of native or residual nitrogen in certain soils.
This phenomenon was first reported by Dyer (20), whose data
showed that nitrogen concentrations lying as deep as 25 to
50 feet in a virgin Panoche soil near the Coast Range foot-
hills exceeded 1,400 milligrams per liter. Doneen (26)
observed high nitrates in shallow ground water in irrigated
Panoche and Oxalis soils. Later, Doneen, et al (27), in 'an
economic study on the potential agricultural development of
new lands in the southwest San Joaquin Valley, again
observed high nitrate-nitrogen levels in virgin Panoche and
Panhill soils. Deep boring investigations (15) conducted
by the Agricultural Research Service showed moderate to high
nitrate values at depths of 20 to 60 feet in west side
Panoche soils which were farmed. Nitrate values in Hesperia
and Tujunga soils, which are located on the east side of
the Valley, were significantly lower in nitrates at greater
depths (Figure 16). Three tile drainage systems located
along the east side of the Valley, but in different loca-
tions than the plots mentioned above, also showed evidence
of low nitrogen concentrations. These systems, which were
not actually included in the regular nutrient monitoring
program, were monitored periodically from June through
December 19&7; "t*16 combined drainage averaged 10 mg/1
nitrate-nitrogen. Quantities of nitrate in terms of pounds
above the water table were determined at separate borings
for each plot. The data are illustrated in Figures 17 and
18. From these investigations, the ARS determined that
fertilizer application could not possibly account for the
large amounts of nitrates found in the west side Panoche
profiles.
These independent observations of nitrates in soils were a
prelude to investigations of residual soil nitrogen initi-
ated by the Department of Water Resources. Soil profiles
69
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FIGURE 16- NITRATE CONCENTRATIONS WITHIN DEEP PROFILES
OF EAST AND WEST SIDE SOILS
100
200
I Z 3 4 5 678910 20 JO 10 50
AVERAGE NOj POUNDS PER ACRE FOOT
FIGURE 17- QUANTITIES OF NITRATE IN DEEP PROFILES OF EAST AND WEST SIDE SOILS
50
5000
10000
100 250 5OO IOOO 2500
AVERAGE NOj POUNDS PER ACRE FOOT
FIGURE 18-QUANTITIES OF NITRATE ABOVE THE WATER TABLE IN DEEP PROFILES OF
EAST AND WEST SIDE SOILS
25OOO 50000
70
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representing the major soil series and physiographic posi-
tions were sampled in an area extending from Tracy south
along the west side to Lost Hills. Forty-five sites were
sampled to a depth of 10 feet or more; samples were collected
at incremental depths not exceeding 3 feet. Virgin sites
were sought to obtain the quantity of nitrogen in the soil
before irrigation. Several dry-farmed and irrigated sites
were also sampled.
Ranges and Magnitudes
Nitrogen concentrations within individual profiles varied
considerably between sites and with depth; leaching was
apparent at the surface of nearly all virgin profiles sampled,
Table 20 is a virgin profile of the Panhill series and is an
example of the variability of nitrogen by depth. The distri-
bution of nitrogen throughout the profile is typical of
similar virgin sites and other related soil profiles investi-
gated in the area. As the example shows, nitrogen in the
first foot or more has been leached. An inverse condition
was found for many irrigated soils which were fertilized.
Therefore, for this study only the samples from 3 to 10 feet
were considered representative of nitrogen in the tile zone.
(Tile laterals are normally installed at depths between
6 and 9 feet.) This was done to make the most accurate
assessment of the average nitrogen conditions in the soil
profile.
TABLE 20
EXTRACT ANALYSIS OP A VIRGIN i ALLUVIAL SOIL
ON THE WEST SIDE OF THE SAN JOAQUIN VALLEY
•* Saturation: ECxlo6
q1tp :Deoth Ranee : Texture •* Saturation: ECxlo : NOQ-N
Site .ueptn nange. iexture ;PerCentage;of Extract; (mg/l)
N-6 0 - 1.5 loam 42.8 515 18.0
(Panhill
Series) 2.5 - 4.0 sandy clay 43.6 5,270 83.5
loam
4.8 - 5.7 fine sandy 32.8 6,575 257.0
loam
6.5 - 8.2 loam 37.6 6,240 242.0
9.2 -10.4 fine sandy 32.6 5,985 208.0
loam
71
-------
Nitrogen concentrations were averaged (depth-weighted) and
grouped by soil series and site conditions. All irrigated
sites were assumed to have been fertilized; dry-farmed sites
were counted as receiving minimum fertilization and were
therefore combined with virgin sites of the same soil series
in the analysis. When interfan areas were so noted, they
were analyzed separately from the main body of alluvial
soils in order to determine the extent of natural leaching
that took place. The average nitrogen levels for individual
sites are given in Table 21.
TABLE 21
AVERAGE!' NITROGEN CONCENTRATIONS IN VIRGIN, IRRIGATED,
AND DRY FARMED SOIL PROFILES ALONG THE WEST SIDE
OF THE SAN JOAQUIN VALLEY
Site
Number
N-l
N-2
N-3
K-lt
N-5
N-13
N-17
PO .
N-8
N-9
H-10
N-ll
N-6
N-7
H-12
N-lU
N-15
N-18
N-16
N-1S
N-25
N-20
N-2U
N-28
N-29
H-26
N-27
N-30
N-21
K-22
N-23
N-31
N-32
N-33
N-3«
N-35
N-36
N-37
N-33
N-5o
N-<42
N-39
N-53
N-lll
X-bit
Phys.i/
Position
BR
BR
RA
RA
BR
OA
RA
RA
BR
BR
BR
£R
RA
RA
RA
RA
RA
RA
RA
RA
RA
RA
RA
RA
RA
RA
RA
RA
RA
RA
RA
T
OA
T
RA
OA
OA
OA
RA
RA
OA
OA
RA
OA
RA
Series
Name
Lethent
Lethent
Panhlll
Panhlll
Lethent
Lost Hills
Panoche
Panoche
Volta
Orestimba
Oreatimba
RoaBl
Panhlll
Panhlll
Panhlll
Panoche
Panoche
Panoche
Panoche
Panoche
Panoche
Panoche
Panoche
Panoche
Panoche
Panoche
Panoche
Panoche
Panoche
Panoche
Panoche
Denver ton
Rir.con
Los Banoa
Panhlll
Lost Hills
Lost Hills
Lost Hills
Panhlll
Sorrento
Lost Hills
Rincon
Ambrose
Zaimra
Sorrento
Soil
Type*.'
sc
sc
si
si
cl
1
1
1
scl
c
cl
cl
1
1
1
1
1
fal
cl
1
fsl
sic
sic
sic
aic
sic
sic
sic
sic
sic
1
c
cl
1
1
1
1
cl
fsl
la
1
cl
c
cl
fal
Nitrogen
in Tile
Zone
(mg/D
113
171
167
35
1
I;
1
2
1
1
1
5
209
12
165
235
233
27
21
16
"7
8
8
6
12
80
16
25
9&
6l
«9
33
15
u
8
«2
10
206
19"!
32
3
2
59
0
17
; Field Condition Modifiers
•Virgin
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Irrlg.
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
:Fert. :Dry-F.
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Field Observation Notes
Restricted permeability.
Restricted permeability.
Relatively unleached.
Relatively unleached.
Main stream course.
Main stream course.
Main atream courae.
Main stream course.
Subject to frequent high water
Subject to frequent high water
Interfan area.
Near creek.
Interfan area.
Upper fan area.
Upper fan area.
Small fan bottom.
Close proximity of farmed area
Close proximity of farmed area
Intensively farmed.
Intensively farmed.
Near open drain.
Upslope from open drain.
Upalope from open drain.
Lower end of cotton field.
Near open drain.
Center of field.
Intensively farmed.
Intensively farmed.
Sampled on fence line.
Alluvial bottom.
Terrace soil.
High fan position.
High fan position.
Coarse textured subsoil.
Near gypsum tnlnes.
Near gypsum mines.
Near Kettlenan Hills.
Coarse textured profile.
Underlain by gravel.
Deposited by Patterson Creek.
table.
table.
table.
table.
Deposited by Corral Hollow Creek.
Deposited by Lone Tree Creek.
I/ Average - depth weighted NOj-N in tile zone (3 - 10 feet).
?/ Physiographic positions: BR « basin rim, RA « recent alluvium fan, OA » older alluvial fan, T » terrace.
][/ Surface texture: ac « sandy clay, si » sandy loam, cl - clay loam, 1 « loam, acl - sandy clay loam,
fsl • fine sandy loam, sic » sllty clay, la - loamy sand, c - clay.
Variability of Nitrogen from Different Sites
Average nitrogen concentrations within individual profiles
of different soil series varied from 0.0 mg/1 to 23^ mg/1;
concentrations exceeding 400 mg/1 were observed at depth in
72
-------
some samples. Nitrogen concentrations were found to be
higher for virgin than for Irrigated soils of the same
series. Also, extreme differences in nitrogen concentrations
were observed between soils occupying different physiographic
positions; interfan areas were higher in nitrogen than was
the main body of the alluvial fan.
Virgin Sites. The highest concentrations observed were
found in two virgin profiles of Panoche soil series; nitrogen
values averaged 233 and 234 mg/1 in the tile zone. High
nitrogen concentrations were also found in soil extracts
taken from virgin profiles of the Lost Hills and Panhill
series, close relatives of the Panoche series. However, low
to moderate levels of nitrogen were also observed in some
virgin profiles of these soils where natural leaching
occurred.
Irrigated Sites. Two irrigated sites of Lethent series
located in the basin rim physiographic position were nearly
as high in nitrogen as some of the virgin alluvial sites
mentioned above. One experimental tile system which was
mentioned previously in this report had nitrate-nitrogen
concentrations exceeding 2,000 mg/1. However, soil condi-
tions at these sites were not considered representative of
other known basin rim areas where tile systems have been
installed. Pour basin rim sites, which included one site of
Rossi, one of Volta and two of the Orestimba soil series,
averaged 4 mg/1, which correlated closely with tile drainage
from soils in similar physiographic positions, but from
different soil series .
In several profiles of the Panoche series examined in irriga-
ted areas, nitrogen ranged from 6 to 94 mg/1 and averaged
about 37 mg/1 in the saturation extracts. Only one irrigated
site of Panhill soil was sampled; nitrogen averaged 35 mg/1.
Table 22 compares the average nitrogen for virgin soils to
that of irrigated soils. The data show that nitrogen is
significantly higher in virgin soils.
Alluvial Pan and Interfan Sites. Soil samples collected
From virgin sites" within ~lhe main course of a depositing
stream are usually well leached and contain less nitrogen
than soils located In interfan areas. The extent of natural
leaching depends mainly upon the texture and stratigraphy of
the soil, precipitation, and relative proximity to a stream
or creek at one time or another. The data,compiled in
Table 23 show that nitrogen is much more concentrated in the
soils sampled from alluvial interfan areas than from fan
areas in the direct course of a depositing stream.
73
-------
TABLE 22
NITROGEN IN VIRGIN AND
IRRIGATED SOIL PROFILES
: Virgin SoilsL/
Soil :
Series :^; °
.Sites
•
Panoche
Panhill
Lost Hills
Sorrento
7
6
5
1
_: N03-N (mg/1)
^Profile: ,,
O f A \7 OT*Q D* ^ 3f
• 1? Q v^ *y A ^— f * ^^ * ^ "• ^^C> Sit
1
8
4
- 234
- 209
- 206
—
76
126
66
32
1 Irrigated Soils
: : N03-N
(mg/1)
^:^Y:o^r: Prof lie: o/
.Sites ;Range27:Average^/
11 6-94
1
1 — —
1
37
35
3
17
I/ Virgin and dry-farmed sites.
2~/ Range of concentrations between different sites.
Average nitrate-nitrogen in tile zone, depth-weighted.
TABLE 23
RESIDUAL NITROGEN IN VIRGIN SOIL
PROFILES OF ALLUVIAL FAN AND INTERFAN AREAS
Soil
Series
Panoche
Panhill
Lost Hills
Sorrento
Rincon
: ' Alluvial Fani/
: No. of
: Sites
3
1
3
1
2
: Average N03-N
: (mfe/1)
10
12
5
17
8
: Alluvial Interfan
: No. of
: Sites
2
6
2
1
—
: Average NO^-N
(mg/ir
23^
130
120
32
—
I/ Selected in the main course of the depositing stream.
-------
Interfan areas are those which are protected from repeated
flushing action of a nearby stream by their slightly higher
elevation. Interfan areas are interspersed with the many
coalescing alluvial fans on the west side.
Different Geographical Sites. Soil profiles located in the
northern area tended to be lower in nitrogen than were the
soils investigated in the central area. Values ranged from
2 mg/1 for one Rincon site to 59 mg/1 at a site of Ambrose
soil; both sites were dry-farmed. Drainage from three tile
systems located in Ambrose soil never approached this value.
More sites are needed in the northern area to evaluate the
magnitudes of residual nitrogen in virgin and irrigated soil
profiles.
Nitrogen in Soils and Tile_Dra_inag_e
Whenever possible, comparisons were made between the
nitrogen found in soils (saturation extracts and field
extracts) and that of tile drains, either in the same tiled
field, nearby field, or the same soil series located some
distance away. However, much variability exists in soils,
and soils data were somewhat limited; therefore, only a few
comparisons could be made.
Saturation Extracts and Field Extracts. The most universally
accepted method Tor determining specific ions in soil samples
is the analysis of soil solutions known as the saturation
extract (28). The extracts are prepared by adding distilled
water to an oven-dried soil sample until a condition of
saturation is reached. The leachate then is extracted by
means of a suction filter device. The water content of a
saturated paste generally exceeds that found in the soil
under saturated field conditions be.cause of the lower volume
weight and greater porosity. The saturation percentage (SP)
is expressed as grams of water per 100 grams of soil.
Soil solutions extracted from saturated soil pastes have
been determined to be as near as possible to the water
content which occurs under field conditions. However, the
concentration of salts in tile drainage cannot be expected
to be exactly the same as that in saturation extracts. As a
soil approaches the permanent wilting point (PwT), the soil
solution becomes much more concentrated. The PWP varies
for different soils and is generally expressed as the
percent of moisture in a soil on a dry-weight basis at
which plants wilt and are unable to regain turgidity.
75
-------
The moisture content of the soil fluctuates between the
lower limit represented by PWP and the upper or wet end of
the available moisture range — field capacity (FC). FC,
which is defined as the amount of moisture retained by a
given soil after a period of free drainage, is approximately
twice the PWP. Tests have shown that the SP over a wide
textural range is equal to four times the PWP. Therefore,
the salt concentration in a saturated extract is roughly
one-half that of the soil solution at FC and one-fourth the
concentration of the soil solution at the PWP.
Soil-Moisture Relationships. In addition to the difficulty
evident in the selection of samples representative of
average soil conditions from a given field and the bio-
chemical disturbances created during soil preparation in
the laboratory, certain field conditions exist which cannot
be duplicated. For example, tiled fields seldom occupy
areas having the homogeneity that is found in a small sample
of soil. Stratigraphic and structural variability is
prevalent in the soils on the west side of the Valley.
Efficient tile operation is dependent upon the presence of
coarse-textured material within the soil profile; therefore,
certain portions of fields are not only drained at different
times depending upon the portion of the field being irriga-
ted, but also at different rates depending upon differences
in soil permeability and lateral hydraulic conductivity.
Vast areas of soils along the west side have been classified
as having greater lateral than vertical hydraulic conduc-
tivity (29). These soil conditions were somewhat substantia-
ted by the quantities of effluent discharged from several
tile systems investigated in the study area.
Whenever tile systems are installed in soils such as those
just described, the coarse-textured material (aquifers) is
leached rapidly and the finer textured portions of a field
are leached more slowly. The intensity of irrigation and
its duration may determine to some extent the effective
leaching of these fine-textured regions of a field. (These
isolated conditions are seldom shown on a soils map.) These
dense areas approach saturation more slowly than the coarse-
textured areas during normal irrigation. If nitrate ions or
other ions are present, they may not have the opportunity
to solvate and drain into the shallow ground water. There-
fore, soil moisture extracted directly from the field by
means of porous cups may be more indicative of the actual
field salinity and soil nitrate levels than saturated
extracts. The number of samples collected and timing of
sampling (for different periods of agricultural activity),
the depths sampled and the specific textural areas sampled
all play an important part in obtaining a soil sample repre-
sentative of moisture and salt conditions within an entire
76
-------
field area. Considerable time was spent for field explora-
tion before sites were selected for the in-field moisture
sampling.
Field Comparisons. During 1966, a cooperative investigation
Between the Department of Water Resources, the Environmental
Protection Agency (EPA) (then the Federal Water Quality
Administration), and the University of California at Davis
was conducted in the Firebaugh area. Soil samples were
collected from several fields and samples were analyzed for
nitrates and other minerals. These investigations revealed
moderate concentrations of nitrogen in the saturation
extracts collected from three irrigated Panoche soils.
Nitrogen concentrations in the tile drainage were much
higher, as shown by comparison in Table 24.
TABLE 24
NITROGEN CONCENTRATIONS IN SATURATION EXTRACTS AND
DRAINAGE FROM THREE TILED FIELDS OF THE PANOCHE SERIES
1966
~y ^Concentrations of NO^-N (mg/1) .
:Saturation Extracts: Tile Draina|e£/
; Profile-Ranged/; Average^/; 1966: 19&7; 19QO1: 19b
-------
of suction devices (porous cups) installed at 1-foot
increments up to 4 feet in depth at several locations within
the tiled fields. The data show average nitrogen concentra-
tions in the field moisture between 1 and 4 feet compared to
the average concentrations observed during the same year for
each tile system (Table 25). Field moisture samples from
the surface (0 to 1 foot) contained much higher nitrogen
concentrations than did the subsurface and subsoil samples.
These high values were presumed to be influenced from ferti-
lizers and were not included in the averages.
TABLE 25
NITROGEN CONCENTRATIONS IN FIELD MOISTURE
AND DRAINAGE FROM FOUR TILED FIELDS
1967
Field
Code
* •
: Soil I
: Series :
Soil
Type
: N03-N : Average N03-N
: (mgA): (mgA)
zProfile: Field .: Tile .
:Range±/:Moisture£' :Drainage2/
BFS 8003 Oxalis Silty clay 17 - 39 25
FBH 5056 Panoche Silty clay 18 - 53 33
DPS 1016 Panoche Loam 16 -284 94
FBH 4045 Panoche Fine sandy 36 - 64 48
loam
6
37
28
19
I/ Range of concentrations by depth within the field.
£/ Samples were extracted from porous cup devices within
the fields.
3/ Weighted average concentrations.
From the data presented in the two foregoing tables, very
little correlation seems to exist between the nitrogen
concentrations in soil moisture collected from the field and
that observed in tile drainage.
Nitrogen in saturation extracts of different irrigated soils
(Table 21) is compared to that observed in tile drainage
(1967-68 averages) from the same-named soil series (Table 26)
A close correlation was found in only one out of six soil
series examined. This was for the Panoche series where there
was a sufficient number of samples represented in each case.
78
-------
TABLE 26
NITROGEN CONCENTRATIONS IN SATURATION
EXTRACTS AND TILE DRAINAGE FROM IRRIGATED SITES
Soil
Series :
Physiographic
Position
. Saturation •
! No. '. Extracts !»<>. of .Tile Drainage
i of ; Average^/ ': Tile ': Average^/
.Sites.Systems.ro^-N (mg/1)
Ambrose Older alluvial fan 1 59
Lethent Basin rim 2 142
3
2
T
20
Lost
Hills
Panhill
Panoche
Sorrento
Older alluvial fan
Recent
Recent
Recent
alluvial
alluvial
alluvial
fan
fan
fan
1
1
11
1
3
35
37
17
3 5*»
k 1*5
8 38
6 11
I/ Average N03-N in soil from 1 to 8 feet, 1966-67.
£/ Weighted average concentrations over two years, 1967-68.
Comparisons of nitrogen concentrations of extracts and tile
drainage from similar virgin soils could not be made because
tile systems are rarely installed in virgin areas.
Saturation extracts of virgin Panoche and related soils
(Panhill and Lost Hills, Table 21) of one area averaged
06 mg/1 in the tile zone. Tile drainage from another area
of Panoche soils, farmed but not previously tiled, averaged
44 mg/1, considerably less than that found in the saturation
extracts.
Future Tile Drainage
Tile drainage system installation is expected to continue in
the northern area (Byron-Westley and Westley-Gustine).
Tentative plans have been made for installations south of
the town of Tracy and near the towns of Patterson and Newman.
Tile systems have been Installed nearly every year in the
Gustine-Mendota area and are expected to continue, especially
since the introduction of plastic conduit. In the Tulare
Lake area, the number of tile drainage systems has not
79
-------
increased since 1966. Tile drainage discharges for future
periods from these and other areas have been predicted by
the San Joaquin Valley Drainage Advisory Group (30).
San Luis Unit Service Area
One of the most important areas to consider from the stand-
point of future drainage is the Federal San Luis Unit Service
Area. The U. S. Bureau of Reclamation estimates that the
annual agricultural wastewater disposal requirement (30) .
will reach 155*000 acre-feet in 50 years and is expected to
exceed this by 2035. This amounts to better than one-third
the total volume predicted from the entire San Joaquin
Valley for the same period.
An important consideration, aside from the quantity of
drainage from this area, is the expected nitrogen content.
If the drainage is high in nitrogen, it could raise the
predicted levels higher than anticipated and could also
affect the seasonal variability of nutrient concentrations.
Soils within the SLUSA are among those already mentioned:
Panoche, Panhill, Lost Hills, Oxalis, Levis, and Lethent.
However, according to the tile drainage plans proposed by
Westlands Water District, the largest amount of the 300,000
acres that are to be drained will be located along the
eastern portion of the area near the trough, which is
represented mostly by the Oxalis soil series of the basin
rim physiographic position. The Lethent and Levis series
also occupy sizable acreages in the area. There also may be
some influence from Panoche soils where tile system laterals
extend into the lower alluvial fan position.
According to findings mentioned in previous sections of this
report, tile drainage from basin rim and basin position
soils in the nearby Gustine-Mendota area was never found to
be high in nitrogen. Moderate concentrations were observed
in a few tile drains where soils of recent alluvial fans
merge with soils of the basin rim position. Therefore, tile
drainage data would seem to indicate that nitrogen concentra-
tions from the basin rim soils in the San Luis Unit Service
Area would be lower than 33 mg/1, the 1967-68 average for
the Gustine-Mendota area. This area consists mostly of
soils occupying recent alluvial fans.
However, in some cases basin rim soils appear to contain
high nitrates. Investigations by the Department have shown
that residual nitrogen in soils of the basin rim was quite
low, except for two sites of Lethent soils located in the
north end of the SLUSA. The USER found sites of high
80
-------
nitrate-nitrogen at two sites of west side soils during
collection of soil material for its lysimeter studies (22).
The initial leachate collected from the lysimeters filled
with Oxalis and Panoche soils ranged respectively from
564 to 4,515 mg/1 nitrate-nitrogen. These high concentra-
tions were attributed to disturbances and aeration resulting
in rapid nitrification of organic matter. After leaching,
the nitrogen concentrations reached static levels of
25 mg/1 for Panoche and 226 rag/1 for Oxalis, which were
very close to the concentrations observed in the initial
soil-water extracts taken at the time the soil was removed
from the field. Further investigations of soil nitrogen by
USER in the SLUSA revealed variable concentrations of
nitrogen in irrigated soil profiles. Thirteen sites were
sampled in four transects across the Valley; five holes
were bored at each site to depths of 40 feet in some cases.
The range and average nitrogen concentration for the tile
zone (3 to 10 feet) at each site are given in Table 27.
TABLE 27
NITRATE-NITROGEN CONCENTRATIONS IN
IRRIGATED WEST SIDE SOILS INVESTIGATED BY USER
Range of :.,,_ M~ M .._
o «, c < „ „, N03-N in s. NO-N In
No.:Soil Series and Type.Sat> £:SoirProfiles:
(mg/l)2/
1
2
3
4
5
6
7
8
9
10
11
12
13
Oxalis silty clay
Lethent silty clay
Panoche clay loam
Panoche silty clay
Oxalis clay ~j
Lethent clays!/
Levis silty clay
Oxalis silty clay
Panoche silty clay
Lost Hills silty clay
Panoche clay loam
Panoche silty clay
Oxalis silty clay
49
48
43
50
67
60
78
87
46
51
36
64
68
3
0
0
0
0
2
1
1
2
4
4
1
0
- 99
- 27
- 18
- 49
- 68
- 71
- 22
- 482
- 129
- 228
- 195
- 125
- 38
19.0
4.0
5.0
16.0
24.0
9.0
8.0
206.0
18.0
109.0
35.0
20.0
5.0
I/ Average saturation percentage.
;?/ Range of NOo-N by depth between sites
3/ Soil was sampled to 5 feet only.
81
-------
Nitrate values in soil-water extracts were averaged,
converted to nitrogen, and divided by the average saturation
percentage to bring the values close to those of saturation
extracts. The highest concentrations were found at one site
of the Oxalis soil series; nitrogen averaged 206 mg/1 in the
tile zone. All other Oxalis sites had low to moderate
concentrations. The next highest concentration was found
at a site of Lost Hills series; nitrogen levels averaged
109 mg/1. Only moderate concentrations of nitrogen were
found in the Panoche series; average concentrations ranged
from 5 to 35 mg/1 at the five sites sampled. These soil
nitrogen values were slightly lower than those found in
saturation extracts of irrigated Panoche soils by the
Department.
If the sites sampled by USER are representative of the soils
in the SLUSA, then future drainage from this area could
possibly be higher in nitrogen than from the Gustine-Mendota
area. All the Oxalis sites sampled from that area averaged
64 mg/1, a value that is much higher than the values indi-
cated in tile drainage or soil samples collected from the
basin rim soils of the Gustine-Mendota area. If the 13
sites investigated by USER are weighted by the number of
borings at each site, the average is 37 mg/1 (Table 28),
close to the two-year average from tile systems in the
Gustine-Mendota area.
TABLE 28
NITRATE-NITROGEN CONCENTRATIONS FOR
DIFFERENT SOIL SERIES INVESTIGATED BY USER
Soil
Series
Lost Hills
Oxalis
Panoche
Levis
Lethent
: No. of :
: Borings :
5
20
25
5
5
NO^-N Img
Profile Rangei/
4 - 228
0 - 482
0 - 195
1-22
4 - 9
/I)
: Average
109
64
19
8
6
o/
Weighted Grand Averaged 37
I/ Maximum and minimum observed within all
profiles sampled.
2/ Weighted by number of borings.
82
-------
Residual Nitrogen in Parent Materials
of West Side Soils
Genesis and Morphology:. The composition of parent rock* is
an important factor in determining soil characteristics in
an area of arid climatic conditions, such as the west side
of the San Joaquin Valley. The rocks of the Diablo Range,
from which all the soils in the study area except the basin
soils of the area have been derived, are classed geologi-
cally as a series of sandstones, shales, and conglomerates
of Cretaceous and earliest Tertiary (Eocene) age (6). It is
from these formations that parent materials of west side
soils have developed.
Soils associated with certain drainage ways of the coastal
foothills contain varying quantities of salts, such as
gypsum, calcium carbonate, and sodium carbonate. Only in
the last few years has interest in nitrates in subsurface
and ground waters developed. Consequently, data on quantity
and quality of nitrates are scarce. As related previously
in this report, several instances of high nitrates have been
found in certain alluvial soils which cannot be accounted
for by fertilization. Existing concentrations in these
profiles vary according to the extent of leaching caused
either by natural streams or by recent irrigation.
Nitrogen Concentrations in Parent Materials
To better understand the persistence of native or residual
nitrogen, one must realize that these soil profiles have
developed in a relatively drv environment '(6 to 8 inches
total precipitation per year]. Plash storms produced many
mud flows; intermittent streamflow, which carried heavy
loads of fine material, subsequently deposited this material
Periods of flooding were followed by periods of rapid
evaporation, which allowed little time for deep percolation.
This developmental process was quite clear to Agricultural
Research Service investigators during their deep boring
studies (15). Findings at two of these plots in Panoche
soils promoted investigations of parent materials in old
drainage ways of the Diablo Range, which were presumed to be
the source of the alluvium. Samples were collected from
several sites in three main arroyos: Ciervo, Hondo, and
*Parent materials are defined (7) as the unconsolidated and
more or less chemically weathered mineral or organic matter
from which the solum of soils is developed under pedogenic
processes.
83
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Big Panoche. They were collected from stratified zones
(hillsides, gullies, and ridges), mud flows, streams and
creeks. Average nitrate-nitrogen was determined for samples
collected in similar zones and is presented in Table 29.
TABLE 29
SUMMARY OF NITRATE-NITROGEN
CONCENTRATIONS POUND IN PARENT
MATERIALSi/ OF WEST SIDE ALLUVIAL FAN SOILS
oiues oa.mpj.eu .
Surface, small delta
Subsurface, small delta 1
Miscellaneous strata
Mud flows (clods)
Mud puddles (water)
Streams (water)
Streambeds (dry)
Creeks (Cantua, Ciervo, Big Panoche)
Arroyos (face, sides, depths)
Ranges :
420.0 -1,820.0
,13^.0 -3,360.0
1.4 -1,890.0
0.3 -5,600.0
0.4 - 3.9
0.07- 3.9
12.4 - 60.0
0.14- 4.2
0.4 -1,169.0
Average
1,120.0
2,240.0
210.0
294.0
1.5
0.7
35.0
2.6
137.2
I/ Tertiary marine sediments at the Coast Range.
Concentrations in 1:1 soil-water extracts.
The data show that extremely high nitrates do exist in
various parent materials. Although a great variability
exists among the sites, these data do provide a sound basis
for determining the source of nitrates that occur in certain
alluvial fan soils. The data also explain the presence of
high nitrogen in tile drainage from these same certain soils
84
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SECTION VI
REFERENCES
l) California State Department of Water Resources. San
Joaquin Master Drain: San Joaquin Valley Drainage
Investigation. Preliminary Edition, Bulletin No. 127.
January 1965•
2) United States Department of Agriculture. Yearbook of
Agriculture. Soils and Men, p. 729, 1938 Edition.
3) Luthin, J. N. (ed.) "Drainage of Agricultural Lands",
Monograph VII. American Society of Agronomy, Madison,
Wisconsin, pp. 79-112. 1957.
4) Johnston, W. R. and A. F. Pillsbury. Drainage Perform-
ance and Waste Water Management in the San Joaquin
Valley of California.1962-63.(Progress Report)
5) Milani, M. J. "Factors Affecting Drainage in the
Northern San Joaquin Valley". A speech presented at
S.C.S. engineers meeting in Santa Barbara, California.
January 18, 1967.
6) Harradine, F. Soils of Western Fresno County,
California. University of California, College of
Agriculture, Agriculture Experiment Station, Berkeley,
California. 1950-
7) Soil Science Society of America. Resource Conservation
Glossary. Journal of Soil and Water Conservation.
Vol. 25, No. 1.pp. 4-52.January-February 1970.
8) California State Department of Conservation. Division
of Mines and Geology. Geologic Map of California.
Santa Cruz (1959) and San Jose (1966).
9) California State Department of Water Resources. West
Side Crop Adaptability Study. Bulletin No. 163.
March 1970.
10) California State Department of Water Resources.
Economic Demand Water in Study Area No. 2, San Joaquin
District. March 25, 19&9. (Memorandum Report)
11) American Public Health Association. Standard Methods
for the Examination of Water and Waste Water,
12th EditiorT 1961T
85
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12) Millar, C. E. "Soil Fertility". John Wiley and Sons
Inc. New York. pp. 299-348. 1965.
13) Lyon, T. L., H. 0. Buckman and N. C. Brady. The
Nature and Properties of 'Soils . The MacMillan Company.
Fifth Edition, p. 463. 1952.
14) Terman, G. L. "Volatilization Loss of Nitrogen as.
Ammonia from Surf ace -Applied Fertilizers". Soils. -and
Fertilizer Research Branch, TVA, Wilson Dam, Alabama.
Agrichemical West, pp. 6-13. December 1965.
15) United States Department of Agriculture, Agricultural
Research Service, Fresno, California. 1959.
(Unpublished data)
16) Ponnamperuma, F. N. "The Mineral Nutrition of the Rice
Plant " . Proceedings of a Symposium at the International
Rice Research Institute" p. 308. February 1964.
1?) Power, J. F. '"What Happens to Fertilizer Nitrogen in
the Soil" . Journal of Soil and Water Conservation.
p. 10. January-February 1968.
18) Meek, B. D., L. B. Grass, and A. J. MacKenzie. "Applied
Nitrogen Losses in Relation to Oxygen Status of Soils" .
Soil Science Society of American Proceedings. Vol. 33,
No. 4, p. 575- July -August 1969.
19) Allison, F. E. "The Enigma of Soil Nitrogen Balance
Sheets". Advances in Agronomy. Vol. 7. 1955.
20) Dyer, Kenneth L. "Interpretation of Chloride and
Nitrate Ion Distribution Patterns in Adjacent Irrigated
and Nonirrigated Panoche Soils" . Soil Science Society
of American Proceedings . Vol. 29, No. 2, pp . 170-17
March-April
21) Johnston, W. P., F. Ittihadieh, R. F. Daum and
A. F. Pills bury. "Nitrogen and Phosphorus in Tile
Drainage Effluent " . Soil Science Society of American
Proceedings. Vol. 29, No. 3, pp. 2«7-2b'9~ May -June
1965":
22) Williford, J. W. and T. C. Tucker. "The Movement of
Nitrogenous Fertilizers Through Soil Columns". Paper
presented at the National Fall Meeting, American Geo-
physical Union, San Francisco, California.
December 15-18, 1969.
86
-------
23) Bower, C. A. and L. V. Wilcox. "Nitrate Content of
the Upper Rio Grande as Influenced by Nitrogen Fertili-
zation of Adjacent Irrigated Lands". Soil Science
Society of American Proceedings. Vol. 33V p. 971.
1969.!
24) California State Department of Water Resources.
"Extraordinary Phosphorous Content in Tile Drainage
Effluent from Tulare Lakebed Soils". 1968.
(Unpublished report)
25) U. S. Department of the Interior. Federal Water
Quality Administration. Role of Soils and Sediment in
Water Pollution Control. 'Part 1, "Reactions of Nitro-
genous and Phosphatic Compounds with Soils and Geologic
Strata", pp. ^3-56. March 1968.
26) Doneen, L. D. "A Study of Nitrate and Mineral Constit-
uents from Tile Drainage in the San Joaquin Valley,
California". A report prepared for the Federal Water
Quality Administration, Pacific Southwest Region,
San Francisco. 1966.
27) Doneen, L. D., et al. "Report No. 2 on Agricultural
Development of New Lands, West Side of the San Joaquin
Valley, Land, Crops and Economics". Department of
Water Science and Engineering, University of California,
Davis. 1968.
28) United States Department of Agriculture, Agricultural
Handbook No. 60, Diagnosis and Improvement of Saline
and Alkali Soils, U. S. Government Printing Office,
p. b1. February 1954.
29) Miller, R. S. and C. F. Anderson'. "Factors Affecting
Drainage on the West Side of the San Joaquin. Valley".
A progress report by the Soil Conservation Service,
U. S. Department of Agriculture. July 11, 1966.
30) San Joaquin Valley Drainage Advisory Group. Final
Report. Fresno, California. January 1969.
87
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SECTION VII
PUBLICATIONS
SAN JQAQUIN PROJECT, FIREBAUGH, CALIFORNIA
1968
"Is Treatment of Agricultural Waste Water Possible?"
Louis A. Beck and Percy P. St. Amant, Jr. Presented
at Fourth International Water Quality Symposium,
San Francisco, California, August 14, 1968; published
in the proceedings of the meeting.
1969
"Biological Denitrificatlon of Wastewaters by Addition
of Organic Materials"
Perry L. McCarty, Louis A. Beck, and Percy P.
St. Amant, Jr. Presented at the 24th Annual Purdue
Industrial Waste Conference., Purdue University,
Lafayette, Indiana. May 6, 1969.
"Comparison of Nitrate Removal Methods"
Louis A. Beck, Percy P. St. Amant, Jr., and Thomas A.
Tamblyn. Presented at Water Pollution Control
Federation Meeting, Dallas, Texas. October 9, 1969.
"Effect of Surface/Volume Relationship, C02 Addition,
Aeration, and Mixing on Nitrate Utilization by Scenedesmus
Cultures in Subsurface Agricultural Waste Waters^1
James F. Arthur and Randall L. Brown. For publica-
tion in Eutrophication Report by University of
California, Berkeley, California. August 1969.
"Nitrate Removal Studies at the Interagency Agricultural
Wastewater Treatment Center, Firebaugh, California"
Percy P. St. Amant, Jr., and Louis A. Beck. Presented
at 1969 Conference, California Water Pollution Control
Association, Anaheim, California, and published in
the proceedings of the meeting. May 9> 1969*
"Research on Methods of Removing Excess Plant Nutrients
from Water"
Percy P. St. Amant, Jr., and Louis A. Beck. Presented
at 158th National Meeting and Chemical Exposition,
American Chemical Society, New York, New York.
September 8, 1969.
89
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1969
"The Anaerobic Filter for the Denitrlfication of
Agricultural Subsurface Drainage"
Thomas A. Tarablyn, and Bryan R. Sword. Presented at
the 24th Annual Purdue Industrial Waste Conference,
Lafayette, Indiana. May 5-8, 1969.
"Treatment of High Nitrate Waters"
Percy P. St. Amant, Jr., and Perry L. McCarty.
Presented at Annual Conference,. American Water Works
Association, San Diego, California. ' May 21, 1969.
American Water Works Association Journal. Vol. 6l.
No. 12.December iyoy.pp. 059-002.
"The Effects of Nitrogen Removal on the Algal Growth
Potential of San Joaquin Valley Agricultural Tile
Drainage Effluents"
Randall L. Brown, Richard C. Bain, Jr., and Milton G.
Tunzi. Presented at the American Geophysical Union
National Pall Meeting, Hydrology Section, San
Francisco, California, December 15-18, 1969.
"Harvesting of Algae Grown in Agricultural Wastewaters"
Bruce A. Butterfield, and James R. Jones. Presented
at the American Geophysical Union National Fall
Meeting, Hydrology Section, San Francisco, California,
December 15-18, 1969.
"Monitoring Nutrients and Pesticides in Subsurface
Agricultural Drainage"
Lawrence R. Glandon, Jr., and Louis A. Beck. Presented
at the American Geophysical Union National Fall Meeting
San Francisco, California, December 16, 1969.
"Combined Nutrient Removal and Transport System for Tile
Drainage from the San Joaquin Valley"
Joel C. Goldman, James F. Arthur, William J. Oswald,
and Louis A. Beck. Presented at the American Geo-
physical Union National Fall Meeting, Hydrology Section,
San Francisco, California, December 15-18, 1969.
"Desalination of Irrigation Return Waters"
Bryan R. Sword. Presented at the American Geophysical
Union National Fall Meeting, Hydrology Section,
San Francisco, California, December 15-18, 1969.
"Algal Nutrient Responses in Agricultural Wastewater"
James F. Arthur, Randall L. Brown, Bruce "\.
Butterfleld, and Joel C. Goldman, Presented at the
American Geophysical Union National Fall Meeting,
Hydrology Section, San Francisco, California,
December 15-18, 1969.
90
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Accession Number
Subject Field & Group
05 B
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
D«partment of Water Resources
San Joaquin District
Fresno, California
Title
NUTRIENTS PROM TILE DRAINAGE SYSTEMS
10
Authors)
Glandon, Lawrence R.
16
EF
21
Project Designation
>A Project 13030 ELY OS/71 -3
Note
Washington, D.C.
22
Citation
Bio-Engineering Aspects of Agricultural Drainage
Pages - 90, Figures - 18, Tables - 29, References - 30
23
Descriptors (Starred first)
'Agricultural Waste, *Tile Drainage, Nutrients, Nitrates, Phosphates,
DBnitrifioation, Fertilization, Irrigation Practices
25
Identifiers (Starred First)
•San Joaquin Valley, California, 'Composited Drainage, 'Nutrient Variability,
Indigenous Nutrients, Residual Nitrogen
27
Abstract
Tile drainage systems of the San Joaquin Valley were monitored for nutrients (nitrogen and phosphorus) to
determine the algal growth potential (AGP) of the waste, and the degree of treatment required for removal of AGP.
The objectives were to determine> (l) the average nutrient concentrations in tile drainage, (2) the magnitudes
of annual, a real and seasonal variability of nutrients and discharges, (3) if a possible correlation exists
between nutrients and agricultural practices, and (4) if existing soil conditions influence nutrient concen-
trations and flows.
• Average discharges and nutrient concentrations were calculated for different years, months and areas of
interest (valleywide, major tiled *r*as, physiographic positions and soils). Average nutrient concentrations
in the composited drainage from the VaJ.ley were found to be 19.3 mg/l for nitrogen (N03-N) and 0.09 mgA
for phosphorus (PO.-P)j average discharge was 1.4 ac-ft/*c/yr. Nutrient levels in the eoraposited drainage
did not change appreciably with time. Variability of nutrients was observed for different seasons} a twofold
decrease in nutrients was attributed to dilution by irrigation and denitrification. N was three times more
concentrated in drainage from one out of four major tiled areas investigated. The high N levels were attributed
more to indigenous concentrations in certain alluvial fan soils and their parent materials than fertilization.
Low N levels found in drainage from basin soils wer« believed caused by devitrification. P was seven times
higher in the drainage from the southernmost area than th« other areas investigated. These extraordinarily
high levels (0.69 mgA) were attributed to indigenous concentrations in certain soils made available by
anaerobic soil conditions. High discharge in the northernmost area (2.3 ao-ft/ac) was believed to be caused
by rapid lateral hydraulic conductivity and surrounding irrigation influence.
Abs tractor
Lawrence R. Glandon
Irixtrtut ion
Department of Water Resources
WR:1O2 (REV. J U !_ Y I969>
WRSI C
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