U.S. ENVIRONMENTAL PROTECTION AGENCY
NATIONAL EUTROPHICATION SURVEY
WORKING PAPER SERIES
REPORT
ON
SILVER LAKE
WORTH COUNTY
IOWA
EPA REGION VII
WORKING PAPER No, 505
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY - CORVALLIS, OREGON
and
ENVIRONMENTAL MONITORING & SUPPORT LABORATORY - LAS VEGAS, NEVADA
•&G.P.O. 699-440
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REPORT
ON
SILVER LAKE
WORTH COIMY
IOWA
EPA REGION VII
WORKING PAPER No, 505
WITH THE COOPERATION OF THE
IOWA DEPARTMENT OF ENVIRONMENTAL QUALITY
AND THE
IOWA NATIONAL GUARD
AUGUST, 1976
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1
CONTENTS
Page
Foreword
List of Iowa Study Lakes iv
Lake and Drainage Area Map v
Sections
I. Conclusions 1
II. Lake and Drainage Basin Characteristics 3
III. Lake Water Quality Summary 4
IV. Nutrient Loadings 8
V. Literature Reviewed 12
VI. Appendices 13
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11
FOREWORD
The National Eutrophication Survey was initiated in 1972 in
response to an Administration commitment to investigate the nation-
wide threat of accelerated eutrophication to freshwater lakes and
reservoirs.
OBJECTIVES
The Survey was designed to develop, in conjunction with state
environmental agencies, information on nutrient sources, concentrations,
and impact on selected freshwater lakes as a basis for formulating
comprehensive and coordinated national , regional, and state management
practices relating to point—source discharge reduction and non-point
source pollution abatement in lake watersheds.
ANALYTIC APPROACH
The mathematical and statistical procedures selected for the
Survey’s eutrophication analysis are based on related concepts that:
a. A generalized representation or model relating
sources, concentrations, and impacts can be constructed.
b. By applying measurements of relevant parameters
associated with lake degradations the generalized model
can be transformed into an operational representation of
a lake, its drainage basin, and related nutrients.
c. With such a transformation, an assessment of the
potential for eutrophication control can be made.
LAKE ANALYSIS
In this report, the first stage of evaluation of lake and water-
shed data collected from the study lake and its drainage basin is
documented. The report is formatted to provide state environmental
agencies with specific information for basin planning [ 3O3(e)], water
quality criteria/standards review [ 3O3(c)], clean lakes [ 3l4(a,b)],
and water quality monitoring [ lO6 and §305(b)] activities mandated
by the Federal Water Pollution Control Act Amendments of 1972.
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111
Beyond the single lake analysis, broader based correlations
between nutrient concentrations (and loading) and trophic condi-
tion are being made to advance the rationale and data base for
refinement of nutrient water quality criteria for the Nation’s
freshwater lakes. Likewise, multivariate evaluations for the
relationships between land use, nutrient export, and trophic
condition, by lake class or use, are being developed to assist
in the formulation of planning guidelines and policies by EPA
and to augment plans implementation by the states.
ACKNOWLEDGMENT
The staff of the National Eutrophication Survey (Office of
Research & Development, U. S. Environmental Protection Agency)
expresses sincere appreciation to the Iowa Department of Environ-
mental Quality for professional involvement, to the Iowa National
Guard for conducting the tributary sampling phase of the Survey,
and to those wastewater treatment plant operators who voluntarily
provided effluent samples and flow data.
The staff of the Water Quality Division of the Department of
Environmental Quality provided invaluable lake documentation and
counsel during the Survey, reviewed the preliminary reports, and
provided critiques most useful in the preparation of this Working
Paper series.
Major General Joseph G. May, the Adjutant General of Iowa,
and Project Officer Colonel Cleadeth P. Woods, who directed the
volunteer efforts of the Iowa National Guardsmen, are also grate-
fully acknowledged for their assistance to the Survey.
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iv
NATIONAL EUTROPHICATION SURVEY
STUDY LAKES
STATE OF IOWA
LAKE NAME COUNTY
Ahquabi Warren
Big Creek Reservoir Polk
Black Hawk Sac
Clear Cerro Gordo
Darling Washington
Lost Island Clay, Palo Alto
MacBride Johnson
Prairie Rose Shelby
Rathbun Reservoir Appanoose, Wayne
Red Rock Reservoir Marion
Rock Creek Jasper
Silver Worth
Spirit Dickinson
Viking Montgomery
West Okoboji Dickinson
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MINNESOTA
IOWA
Silver Lake
01 /outlet
Y
SILVER
Map Location
433O’
. .
SILVER LAKE
Tributary Sampling
x
Site
jKm.
I I
I i Mi.
Lake Sampling Site
Al
I
Lake
4328
93• 26
93 24’
9322
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SILVER LAKE
STORET NO. 1912
I. CONCLUSIONS
A. Trophic Condition:
Survey data indicate that Silver Lake is eutrophic. It
ranked last in overall trophic quality when the fifteen Iowa
lakes and reservoirs sampled in 1974 were compared using a com-
bination of six lake paranleters*. All of the other water bodies
had less median total phosphorus and mean chlorophyll a, 13 had
less median orthophosphorus, eight had less median inorganic
nitrogen, and 13 had greater mean Secchi disc transparency.
Survey limnologists did not observe surface algal concentrations
during sampling visits. However, the numbers of phytoplankton in
July and September indicate that blooms were in progress at those
times (see page 6).
B. Rate-Limiting Nutrient:
The algal assay results indicate that Silver Lake was
limited by phosphorus at the time the assay sample was collected
(04/18/74). The lake data indicate phosphorus limitation in
April and nitrogen limitation in September.
C. Nutrient Controllability:
1. Point sources-—No known point sources impacted Silver
Lake during the sampling year.
* See Appendix A.
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2
It is calculated that the lake received a total phosphorus
loading of 0.24 g/m 2 /yr which exceeds that proposed by Vollen-
welder (Vollenweider and Dillon, 1974) as a eutrophic loading
(see page 11).
Survey limnologists noted that Silver Lake is surrounded by
farms, and it is possible that the estimate of the phosphorus
load from the minor tributary and immediate drainage area of
the lake is too low.
2. Non-point sources--All of the phosphorus entering the
lake during the sampling year came from non-point sources.
Tributary A-2 contributed about 32% of the total phosphorus
load, and the minor tributaries and immediate drainage were
estimated to have added about 60% of the total phosphorus load.
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Drainage
area (km 2 )*
2.4
4.5
6.9
8.2**
Mean flow
( m 3 /sec)*
0.01
0.03
0.04
0 .04
t Table of metric conversions--Appendix B.
ft Harrison, 1975.
* For limits of accuracy, see Working Paper No. 175, “...Survey Methods,
1973-1976”.
** Includes area of lake.
*** See Working Paper No. 175.
3
II. LAKE AND DRAINAGE BASIN CHARACTERISTICSt
A. Lake Morphometrytt:
1. Surface area: 1.29 kilometers 2 .
2. Mean depth: 1.2 meters.
3. Maximum depth: 1.8 meters.
4. Volume: 1.548 x 106 in 3 .
5. Mean hydraulic retention time: 1.2 years.
B. Tributary and Outlet:
(See Appendix C for flow data)
1. Tributaries -
Name
Silver Lake Marsh Outlet
Minor tributaries &
immediate drainage -
Totals
2. Outlet -
Goose Creek
C. Precipitation***:
1. Year of sampling: 63.6 centimeters.
2. Mean annual: 78.3 centimeters.
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4
III. LAKE WATER QUALITY SUMMARY
Silver Lake was sampled three times during the open-water season
of 1974 by means of a pontoon-equipped Huey helicopter. Each time,
samples for physical and chemical parameters were collected from
two or more depths at a single station on the lake (see map, page v).
During each visit, a depth-integrated (near bottom to surface) sample
was collected for phytoplankton identification and enumeration; and
a similar sample was collected for chlorophyll a analysis. During the
first visit, an 18.9-liter depth-integrated sample was collected
for algal assays. The maximum depth sampled was 1.5 meters.
The sampling results are presented in full in Appendix D and are
summarized in the following table (the July nutrient samples were not
properly preserved and were not analyzed).
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A. SUMMARY OF PHYSICAL AND
CHEMICAL CHARACTERISTICS FOR SILVER LAKE
STORET CODE 1912
1ST SAMPLING ( 4/18/74)
2ND SAMPLING ( 7/ 3/74)
3RD SAMPLING C
9/23/74)
1 SITES
I SITES
1 SITES
PARAMETER
RANGE MEAN MEDIAN
RANGE MEAN MEDIAN
HANGE MEAN
MEDIAN
TEMP (C)
10.5 — 10.5 10.5 10.5
23.8 — 23.8 23.8 23.8
13.0 — 13.0 13.0
13.0
DISS OXY (MG/L)
10.0 — 10.0 10.0 10.0
5.0 — 6.0 5.5 5.5
8.4 — 10.2 9.3
9.3
CNDCTVY (MCROMO)
115. 168. 142. 142.
273. — 282. 278. 278.
148. — 149. 149.
149.
PH (STAND UNITS)
8.5 — 8.S 8.5 8.5
8.9 — 9.0 8.9 8.9
9.3 — 9.6 9.5
9.5
TOT ALK (MG/I)
139. — 143. 141. 141.
a•e
78. — 81. 80.
80.
TOT P (MG/L)
0.080 — 0.482 0.281 0.281
******
0.187 — 0.200 0.193
0.193
ORTHO P (MG/U
0.018 — 0.038 0.028 0.028
Q•000•
0.033 — 0.035 0.034
0.034
M02.NO3 (MG/Li
0.720 — 0.820 0.770 0.770
•* O
0.040 — 0.040 0.040
0.040
AMMONIA (MGIL)
0.330 — 0.390 0.360 0.360
‘• ‘
0.040 — 0.040 0.040
0.040
KJEL N (MG/L)
2.500 11.800 7.150 7.150
0O*
4.100 — 4.600 4.350
4.350
INORG N (MG/U
1.050 — 1.210 1.130 1.130
°° —°°° ‘
0.080 0.080 0.080
0.080
TOTAL N (MG/L)
3.220 —12.620 7.920 7.920
Q ***
4.140 — 4.640 4.390
4.390
CHLRPYL A (UG/L)
20.5 — 20.5 20.5 20.5
174.7 — 174.7 174.7 174.7
90.7 — 90.7 90.7
90.7
SECCHI (METERS)
0.6 — 0.6 0.6 0.6
0.4 — 0.4 0.4 0.4
0.3 — 0.3 0.3
0.3
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6
B. Biological characteristics:
1. Phytoplankton* -
Sampi ing
Date
07/03/ 74
Dominant
Genera
1. Lyngbya • .
2. Aphanizomenon p.
3. Melosira .
4. Synedra p.
5. Scenedesmus .
Other genera
Total
Algal Units
per ml
47,518
10,914
5,022
4,443
3,477
11,299
82,673
Sampl ing
Date
04/1 8/74
07/03/74
09/23/ 74
1. Lyngbya .
2. Aphanizomenon p..
3. Microcystis • p.
4. Scenedesmus p•.
5. Aphanocapsa !p.
Other genera
Station
Number
184,949
10,192
8,281
2,549
1 ,274
4,672
211,917
Chlorophyll -
( ig/l)
20.5
174.7
90.7
C. Limiting Nutrient Study:
1. Autociaved, filtered, and nutrient spiked -
Spike (mg/i )
Ortho P
Conc. (mg/i )
Inorganic N
Conc. (mg/i )
Maximum yield
( mg/i-dry wt. )
Control
0.050 P
0.050 P + 1.0 N
1.0 N
0.045
0.095
0.095
0.045
1 .055
1 .055
2.055
2.055
23.6
29.5
39.0
25.4
09/23/74
2. Chlorophyll a -
Total
1
1
1
* The April phytopiankton sample was lost in shipment.
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7
2. Discussion -
The control yield of the assay alga, Selenastrum capri-
cornutum , indicates that the potential primary productivity
of Silver Lake was very high at the time the sample was
collected (04/18/74). Also, a significant increase in yield
with the addition of phosphorus alone indicates that the
lake was limited by phosphorus at that time. Note that the
addition of nitrogen alone resulted in a yield which was
not significantly greater than that of the control.
The lake data indicate phosphorus limitation in April
and nitrogen limitation in September (the mean inorganic nitro-
gen to orthophosphorus ratios were 40 to 1 and 2 to 1, respec-
tively).
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8
IV. NUTRIENT LOADINGS
(See Appendix E for data)
For the determination of nutrient loadings, the Iowa National
Guard collected monthly near-surface grab samples from each of the
tributary sites indicated on the map (page v) in the autumn and
bimonthly samples in the spring. Samples could not be collected from
December through February because of ice cover. Sampling was begun
in August, 1974, and was completed in July, 1975.
Through an interagency agreement, stream flow estimates for the
year of sampling and a “normalized” or average year were provided by
the Iowa District Office of the U.S. Geological Survey for the
tributary sites nearest the lake.
In this report, nutrient loads for sampled tributaries were
determined by using a modification of a U.S. Geological Survey computer
program for calculating stream loadings*.
Nutrient loads for unsampled “minor tributaries and immediate
drainage” (“ZZ” of U.S.G.S.) were estimated using the nutrient loads,
in kg/km 2 /year, at station A-2 and multiplying by the ZZ area in km 2 .
No known point sources impacted Silver Lake during the sampling
year.
* See Working Paper No. 175.
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9
A. Waste Sources:
1. Known municipal - None
2. Known industrial - None
B. Annual Total Phosphorus Loading - Average Year:
1. Inputs —
kgP/ %of
Source yr total
a. Tributaries (non-point load) -
Silver Lake Marsh Outlet 100 31.7
b. Minor tributaries & immediate
drainage (non-point load) - 190 60.3
c. Known municipal STP’s - None
d. Septic tanks - None
e. Known industrial - None - -
f. Direct precipitation* - 25 8.0
Total 315 100.0
2. Outputs -
Lake outlet - Goose Creek 200
3. Net annual P accumulation - 115 kg.
* See Working Paper No. 175.
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10
C. Annual Total Nitrogen Loading - Average Year:
1. Inputs —
kgN/ %of
Source yr total
a. Tributaries (non-point load) -
Silver Lake Marsh Outlet 1,250 25.0
b. Minor tributaries & immediate
drainage (non-point load) — 2,345 47.0
c. Known municipal STP’s - None
d. Septic tanks - None
e. Known industrial - None — -
f. Direct precipitation* - 1,395 28.0
Total 4,990 100.0
2. Outputs -
Lake outlet - Goose Creek 5,495
3. Net annual N loss 505 kg.
0. Non-point Nutrient Export by Subdrainage Area:
Tributary kg P/km 2 /yr kg N/km 2 /yr
Silver Lake Marsh Outlet 42 521
* See Working Paper No. 175.
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11
E. Yearly Loads:
In the following table, the existing phosphorus loadings
are compared to those proposed by Vollenweider (Vollenweider
and Dillon, 1974). Essentially, his “dangerous” loading is
one at which the receiving water would become eutrophic or
remain eutrophic; his “permissible loading is that which
would result in the receiving water remaining oligotrophic
or becoming oligotrophic if morphometry permitted. A meso-
trophic loading would be considered one between “dangerous”
and “permissible”.
Note that Vollenweider’s model may not be applicable to
water bodies with short hydraulic retention times.
Total Phosphorus Total Nitrogen
Total Accumulated Total Accumulated
grams/m 2 /yr 0.24 0.09 3.9 loss*
Vollenweider phosphorus loadings
(g/m 2 /yr) based on mean depth and mean
hydraulic retention time of Silver Lake:
“Dangerous” (eutrophic loading) 0.20
“Permissible” (oligotrophic loading) 0.10
* There was an apparent loss of nitrogen during the sampling year. This
may have been due to nitrogen fixation in the lake, solubilization of
previously sedimented nitrogen, recharge with nitrogen-rich ground water,
or underestimation of the minor tributary and immediate drainage load.
Whatever the cause, a similar nitrogen loss has occurred at Shagawa Lake,
Minnesota, which has been intensively studied by EPA’s former National
Eutrophication and Lake Restoration Branch (Malueg et al., 1975).
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12
V. LITERATURE REVIEWED
Harrison, Harry M., 1975. Personal communication (lake morphometry).
IA Cons. Comm., Des Moines.
Malueg, Kenneth W., D. Phillips Larsen, Donald W. Schults, and
Howard 1. Mercier; 1975. A six-year water, phosphorus, and
nitrogen budget for Shagawa Lake, Minnesota. Jour. Environ.
Qual., vol. 4, no. 2, pp. 236-242.
Vollenweider, R. A., and P. J. Dillon, 1974. The application of
the phosphorus loading concept to eutrophication research.
Natl. Res. Council of Canada Pubi. No. 13690, Canada Centre
for Inland Waters, Burlington, Ontario.
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VI. APPENDICES
APPENDIX A
LAKE RANKINGS
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LAKE DATA TO BE uSLO IN PANPSINGS
LAKE MEDIAN MEDIAN 500— MEAN 15— MEUIAN
CODE LAKE NAME TOTA INO G N MEAN S C Cr1LO A MIN 00 DISS O Tri0 P
1901 LAKE ACOUAtII 0.0 2 0,335 469.333 8.600 8.200 0.009
1902 BIG CREEK RESERVOIR 0.046 6.465 438.500 16.867 14.800 0.011
1903 BLACK NAWK LAKE 0.185 0.130 488.167 49.740 15.000 0.020
190 ’. CLEAR LAKE 0.059 0.070 465.125 17.400 8.600 0.010
1905 LAKE DARLING 0.077 1.475 482.500 13.817 9.200 0.012
1906 LOST ISLAND LAKE 0.146 0.065 421.167 36.100 8.400 0.021
1907 LAKE MACBRIDE 0.061 2.035 458.444 17.067 15.000 0.010
1908 PRAIRIE ROSE LAKE 0.056 0.210 463.667 17.350 8.600 0.010
1909 RATMBUN RESERVOIR 0.071 1.170 475.889 12.039 14.000 0.008
1910 RED ROCK LAKE 0.180 1.880 473.400 14.730 14.000 0.104
1911 ROCK CREEK LAKE 0.065 1.400 480.500 18.367 8.400 0.007
1912 SILVER LAKE 0.193 0.565 482.667 95.300 10.000 0.034
1913 SPIRIT LAKE 0.041 0.090 422.667 12.622 9.000 0.007
1914 VIKING LAKE 0.075 0.130 459.000 26.033 14.200 0.017
1915 WEST LAKE OKOBOJI 0.046 0.060 380.444 7.722 15.000 0.017
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PERCENT OF LAKES WITH HIGHER VALUES (NUMBER OF LAKES WITH HIGHER VALUES)
LAKE MEDIAN MEDIAN 500— MEAN 15— MEDIAN INI)EX
COOL LAKE NAME TOTAL P INO’ G N MEAN SEC CILORA MIN DO DISS thlTpiO P NU
1901 LAKE ACOUA8I 57 ( 8) 50 ( 7) ‘ .3 ( 6) 93 C 13) 100 C 14) 79 C 11) 422
1902 BIG CREEK . (ESERvOIR 89 C 12 0 C 0) 79 ( 11) 57 C 8) 21 ( 3) 50 C 7) 296
1903 8LACK HAWK LAKE 7 C 1) 68 ( 9) 0 C 0) 7 C 1) 7 ( 0) 21 3) 110
1904 CLEAR LAKE 71 C 10) 86 C 12) 50 C 7) 36 ( 5) 75 C 10) 64 8) 382
1905 LAKE DARLING 2? C 4) 21 C 3 14 2) 71 C 10 57 8 ‘.3 23
1908 LOST ISLAND LAKE 21 C 3) 93 C 13) 93 C 13) 1’. C 2) 89 ( 12) 14 C 2) 32’.
1907 LAKE MACBRIDE 64 C 9) 7 C 1) 71 C 10) 50 C 7) 7 C 0) 64 C 8) 263
1908 PRAIRIE ROSE LAKE 79 C 11) 57 C 8) 57 C 8) 43 C 6) 75 C 10) 64 C 8) 375
1909 RATHHIJN RESERVOIR 43 C 6) 36 ( 5) 29 C 4) 86 ( 12) 39 C 5) 86 C 12) 319
1910 RED ROCK LAKE 14 C 2) 14 C 2) 36 C 5) 64 C 9) 39 C 5) 0 C 0) 167
1911 ROCK CREEK LAKE 50 C 7) 29 C 4) 21 C 3) 29 C 4) 89 C 12) 96 C 13) 314
19)2 SILVER LAKE 0 1 0) 43 1 6) 7 C 1) 0 C 0) 50 C 7) 7 ( 1) 107
1913 SPIRIT LAKE 100 C 14) 79 1 11) 86 C 12) 79 C 11) 64 C 9) 96 C 13) 504
191’. ViKING LAKE 36 1 5) 68 C 9) 64 C 9) 21 C 3) 29 C 4 32 C 4) 250
1915 WEST LAKE OKO8OJI
89 1 12) 100 I 14) 100 C 14) 100 ( )4)
7 C 0) 32 C 4) 428
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LAKES RANKED BY INDEX NOS.
RANK LAKE CODE LAKE NAME INDEX NO
1 1913 SPIRIT LAKE 504
2 1915 WEST LAKE OKOBOJI 428
3 1901 LAKE ACOUABI 422
4 1904 CLEAR LAKE 382
5 1908 PRAIRIL ROSE LAKE 375
6 1906 LOST ISLAND LAKE 324
7 1909 RATHBUN RESERVOIR 319
8 1911 ROCK CREEK LAKE 314
9 1902 BIG CREEK RESERvOIR 296
10 1907 LAKE MACBRIDE 263
IL 1914 VIKING LAKE 250
12 1905 LAKE DARLING 235
13 1910 RED ROCK LAKE 167
14 1903 BLACK HAWK LAKE 110
15 1912 SILVER LAKE
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APPENDIX B
CONVERSION FACTORS
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CONVERSION FACTORS
Hectares x 2.471 = acres
Kilometers x 0.6214 = miles
Meters x 3.281 = feet
Cubic meters x 8.107 x 10 = acre/feet
Square kilometers x 0.3861 = square miles
Cubic meters/sec x 35.315 = cubic feet/sec
Centimeters x 0.3937 = inches
Kilograms x 2.205 = pounds
Kilograms/square kilometer x 5.711 = lbs/square mile
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APPENDIX C
TRIBUTARY FLOW DATA
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TRIBUTARY FLOW INFORMATiON FOR IOWA 12/23/75
LAKE CODE 1912 SILVER LAucE
IOTAL DRAINAGE AREA OF LAKE(SO XM) 8.2
SUB—D u AINAGE NORMALIZED FLOIS(CMS)
TRI8UIAPY AREA(SO KM) JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MEAN
191241 8.2 0.01 0.01 0.07 0.13 0.05 0.05 0.03 0.03 0.02 0.02 0.02 0.01 0.04
191242 2.’. 0.00 0.00 0.02 0.04 0.02 0.01 0.01 0.01 0.0) 0.01 0.00 0.00 0.01
1912LZ 5.7 0.01 0.01 0.05 0.09 0.0’. 0.03 0.02 0.02 0.0) 0.02 0.01 0.01 0.03
SUMMARY
TOTAL DRAINAGE AREA OF LAKE 8.2 TOTAL FLOW IN 0.45
SUM OF SOB—DRAINAGE AREAS 8.2 TOTAL FLOW OUT = 0.45
MEAN MONTHLY FLOWS ANU OAILY VLOWS(CMS)
TRIBUTARY MONTH YEAR MEAN FLOW DAY FLOW DAY FLOW DAY FLOW
191241 8 74 0.01 17 0.00
9 7’. 0.00 8 0.00
10 74 0.00 5 0.00
11 74 0.00 3 0.00
12 74 0.00 18 0.00
1 75 0.00 4 0.00
2 75 0.01 2 0.01
3 75 0.04 20 0.01
75 0.23 7 0.14 21 0.25
5 75 0.16 4 0.28 19 0.09
6 75 0.16 10 0.10 23 0.22
7 75 0.09 7 0.16 21 0.04
191 A2 8 74 0.00 17 0.0
9 74 0.00 8 0.00
10 7’. 0.00 5 0.00
11 74 0.00 3 0.00
12 7’. 0.00 18 0.00
1 75 0.00 4 0.00
2 75 0.00 2 0.00
3 75 0.01 20 0.00
4 75 0.07 7 0.04 21 0.07
5 75 0.05 4 0.09 19 0.03
6 75 0.05 10 0.03 23 0.07
7 75 0.03 7 0.05 21 0.01
1912 / 2 8 74 0.00
9 74 0.00
10 7’. 0.00
11 74 0.00
12 74 0.00
1 75 0.00
2 75 0.01
3 75 0.03
4 75 o. le
5 75 0.11
6 75 0.13
7 7S 0.07
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APPENDIX D
PHYSICAL and CHEMICAL DATA
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STORET RETRIEVAL DATE 76/02/02
191201
43 29 00.0 092 25 00.0
SILVER LAKE
19 IOWA
I1EPALES 2111202
4 0007 FEET DEPTH
00010 00300 00077 00094 00400 00410 00610 00625 00630 00671
DATE TIME DEPTH WATER DO TRANSP CNDUCTVY PH T ALK NH3—N TOT KJEL NO2 NO3 PHOS—DIS
FROM OF TEMP SECCHI FIELD CACO3 TOTAL N N—TOTAL ORTHO
TO DAY FEET CENT MG/L INCHES MICROMHO SU MG/L MG/L PIG/L MG/L MG/L P
74/04/18 10 20 0000 10.5 25 115 8.50 143 0.330 2.500 0.720 0.018
10 20 0005 10.5 10.0 168 8.50 139 0.390 11.800 0.820 0.038
74/07/03 10 20 0000 23.8 6.0 15 273 9.00
10 20 0004 23.8 5.0 282 8.90
74/09/23 13 30 0000 13.0 8.4 12 149 9.62 81 0.040 4.100 0.040 0.033
13 30 0005 13.0 10.2 148 9.33 78 0.040 4.600 0.040 0.035
00665 32217 00031
DATE TIME DEPTH PHOS—TOT CHLRPHYL INCDT LT
FROM OF A REPINING
TO DAY FEET MG/L P (JG/L PERCENT
74/04/18 10 20 0000 0.080 20.5
10 20 0005 0.482
74/07/03 10 20 0000 174.7
10 20 0001 50.0
10 20 0003 1.0
74/09/23 13 30 0000 0.181 90.7
13 30 0001 50.0
13 30 0003 1.0
13 30 0005 0.200
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APPENDIX E
TRIBUTARY DATA
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STORET RETRIEVAL DATE 76/01/27
1912A1
43 29 00.0 093 24 00.0
GOOSE CREEK
19 WORTH Co HWY MAP
0/SILVER LAKE
SEC RD 522 BROG 1 MI U OF SILVER LAKE
1IEPALES 2111204
0000 FEET DEPTh
00630 00625 00610 00671 00665
DATE TIME DEPTH N02&N03 TOT KJEL NH3—N PHOS—DIS PHOS—TOT
FROM OF N—TOTAL N TOTAL ORTHO
TO DAY FEET MG/L MG/L MG/I MG/L P MG/L P
74/08/17 08 55 1.260 2.400 0.770 0.020 0.170
74/09/08 14 20 0.704 3.000 1.050 0.020 0.17k
74/10/05 14 45 0.680 2.700 0.880 0.025 0.1 5
74/11/03 12 40 0.850 2.100 0.580 0.052 0.090
75/03/20 15 00 3.300 2.100 0.860 0.065 0.140
75/04/07 14 43 2.700 2.800 0.600 0.030 0.120
75/04/21 13 30 2.200 2.100 0.340 0.020 0.150
75/05/04 09 00 1.650 2.550 0.125 0.035 0.095
75/05/19 10 10 0.500 3.300 0.115 0.025 0.210
75/06/10 10 30 0.440 5.250 1.600 0.020 0.180
75/06/23 10 30 0.460 5.250 1.500 0.100 0.280
75/07/07 13 10 0.525 4.800 2.100 0.110 0.200
75/01/21 13 00 ,970 3.750 0.580 0.065 0.230
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STORET RETRIEVAL DATE 76/01/27
1912A2
43 29 20.0 093 26 10.0
SILVER LK MARSH OUTLET
19 WORTH Co HWY MAP
1/SILVER LAKE
AT S1LVE LAKE MARSH OUTLET CNTRL STRUCT
1 IEPALES 2111204
4 0000 FEET DEPTH
00630 00625 00610 00671 00665
DATE TIME DEPTH N02&N03 TOT KJEL NH3—N PHOS—DIS PHOS—TOT
FROM OF N—TOTAL N TOTAL ORTHO
TO DAY FEET MG/L MG/L MG/L MG/L P MG/L P
74/08/17 09 10 0.028 2.500 0.080 0.110 0.400
74/09/08 14 35 0.016 2.400 0.065 0.045 0.240
76/10/05 15 00 0.128 4.200 0.020 0.080 0.370
74/11/03 12 50 0.016 3.300 0.090 0.110 0.460
15/04/07 14 50 3.900 2.800 1.050 0.055 0.240
75/04/21 13 40 5.600 1.530 0.113 0.040 0.115
75/05/04 09 10 4.900 1.800 0.630 0.027 0.040
75/05/19 10 25 0.025 2.250 0.110 0.200 0.360
75/06/10 10 45 0.005 1.150 0.032 0.120 0.190
75/06/23 10 45 0.005 0.950 0.035 0.105 0.160
75/07/07 13 20 0.015 2.100 0.060 0.260 0.460
75/07/21 13 15 0.015 1.850 0.080 0.180 0.480
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