U.S. ENVIRONMENTAL PROTECTION AGENCY
NATIONAL EUTROPHICATION SURVEY
WORKING PAPER SERIES
REPORT
ON
VEST omeoji U\KE
DICKINSON COIMY
IOWA
EPA REGION VII
WORKING PAPER No, 508
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY - CORVALLIS, OREGON
and
ENVIRONMENTAL MONITORING & SUPPORT LABORATORY - LAS VEGAS, NEVADA
•&G.P.O. 699-440
-------
REPORT
ON
WEST omeoji LAKE
DICKINSON COUNTY
IOWA
EPA REGION VII
WORKING PAPER No, 508
WITH THE COOPERATION OF THE
IOWA DEPARTMENT OF ENVIRONMENTAL QUALITY
AND THE
IOWA NATIONAL GUARD
AUGUST, 1976
-------
CONTENTS
Page
Foreword i i
List of Iowa Study Lakes iv
Lake and Drainage Area Map v
Sections
I. Introduction 1
II. Conclusions 1
III. Lake Characteristics 3
IV. Lake Water Quality Summary 4
V. Literature Reviewed 8
VI. Appendices 9
-------
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 degradation, 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 [§303(e)], water
quality criteria/standards review [§303(c)], clean lakes [§314(a»b)L
and water quality monitoring [§106 and §305(b)] activities mandated
by the Federal Water Pollution Control Act Amendments of 1972.
-------
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.
-------
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
-------
WESTOKOBOJI LAKE
& SPIRIT LAKE
X Lake Sampling Site
1 2
Scale
5Km.
3Mi.
43'3tf~
4320—
9500
I
-------
WEST OKOBOJI LAKE
STORE! NO. 1915
I. INTRODUCTION
West Okoboji Lake was included in the National Eutrophication Survey
as a water body of interest to the Iowa Department of Environmental Quality.
Tributaries and nutrient sources were not sampled, and this report relates
only to the lake sampling data.
West Okoboji Lake, the second largest in surface area of the Iowa
Great Lakes, has the greatest mean depth and largest drainage area of
these lakes. The topography of the watershed is characterized as a gently-
rolling terrain with marshlands of various sizes scattered throughout.
Most of the watershed area is cropland. In another study, animal feedlots
in the watershed were shown to be major contributors of nutrients (Anony-
mous, 1974).
II. CONCLUSIONS
A. Trophic Condition:
Survey data and a report by others (Bachmann and Jones,
1974) indicate that West Okoboji Lake is eutrophic. It ranked
second in overall trophic quality when the 15 Iowa lakes and
reservoirs sampled in 1974 were compared using a combination of
six parameters*. However, based on their more extensive studies,
Bachman and Jones (op. cit.) consider West Okoboji Lake to be of
better trophic quality than .Spirit Lake which ranked first using
using Survey data.
* See Appendix A.
-------
2
One of the other Iowa water bodies had less and one had
the same median total phosphorus, nine had less and one had
the same median dissolved phosphorus, none of the other water
bodies had less median inorganic nitrogen and mean chlorophyll
a^, and none had greater mean Secchi disc transparency. Survey
limnologists reported a phytoplankton bloom in July, but no
higher aquatic vegetation was noted.
Some of the Survey lake data can be compared to data col-
lected during the period of 1971-1972 (Bachman and Jones, op.
cit). The dissolved oxygen concentration show marked depression
at the deepest site during 1971-1972 as well as in 1974. Water
clarity (as measured by a Secchi disc) was greater in 1974, and
chlorophyll a^ levels apparently were higher (possibly indicating
an increase in primary productivity since 1972).
West Okoboji presently satisfies an important recreational
need in the area. The lake is in danger of advanced cultural
eutrophication due to the high nutrient load received from agri-
cultural practices in the watershed (Anonymous, op. cit.).
B. Rate-Limiting Nutrient:
The algal assay results indicate that West Okoboji Lake was
phosphorus limited in April and nitrogen limited in September.
These results are substantiated by the lake data which indicate
«
limitation by phosphorus and nitrogen at the respective sampling
times.
-------
III. LAKE CHARACTERISTICS1"
A. Lake Morphemetry :
1. Surface area: 14.93 kilometers2.
2. Mean depth: 13.7 meters.
3. Maximum depth: 40.8 meters.
4. Volume: 204.541 x 106 m3.
B. Precipitation*:
1. Year of sampling: 71.8 centimeters.
2. Mean annual: 70.5 centimeters.
t Table of metric equivalents—Appendix B.
tt Harrison, 1975.
* See Working Paper No. 175, "...Survey Methods, 1973-1976",
-------
4
IV. LAKE WATER QUALITY SUMMARY
West Okoboji 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
a number of depths at three stations on the lake (see map, page v).
During each visit, a single depth-integrated (4.6 m to surface) sample
was composited from the stations for phytoplankton identification and
enumeration; and during the first and third visits, a single 18.9-
liter depth-integrated sample was composited for algal assays. Also
each time, a depth-integrated sample was collected from each of the
stations for chlorophyll a_analysis. The maximum depths sampled were
18.3 meters at station 1, 39.6 meters at station 2, and 10.7 meters
at station 3.
The sampling results are presented in full in Appendix D and are
summarized in the following table (the July nutrient samples were not
preserved properly and were not analyzed).
-------
A. SUMMARY OF PHYSICAL AND CHEMICAL CHARACTERISTICS FOR WEST LAKE OKOBOJI
STORET CODE 1915
PARAMETER
TEMP (C)
OISS OXY (MG/L)
CNOCTVY (MCROMO)
PH (STAND UNITS)
TOT ALK (MG/L)
TOT P (MG/L)
ORTHO P (MG/L)
N02»N03 (MG/L)
AMMONIA (MG/L)
KJEL N (MG/L)
INORG N (MG/L)
TOTAL N (MG/L)
CHLRPYL A (UG/D
SECCHI (METERS)
1ST SAMPLING ( 4/22/74) 2ND SAMPLING ( 7/ 9/74)
3 SITES 3 SITES
RANGE MEAN MEDIAN RANGE MEAN MEDIAN
6.8 - 7.6 7.1 6.9 12.6 - 23.8 20.6 22. 5
10.4 - 11.8 11.5 11.6 0.2 - 8.2 6.2 7.6
290. - 297. 292. 291. 375. - 461. 436. 450.
196.
0.031
0.003
0.030
0.020
0.800
0.050
0.840
5.1
3.7
212.
- 0.041
- 0.011
• 0.070
- 0.040
- 1.700
~ 0. 1 10
~ 1.770
6.8
3.7
204.
0.036
0.005
0.042
0.027
0.946
0.069
0.988
5.7
3.7
0.030 »«••»• _««*••«»«•«*•••*«»«••»•
0.900 «««««« .«*•*•••«•«*«*»*««»*••«
5.1 6.3 - 14.4 9.4 7.4
3.7 2.4 - 3.4 3.0 3.4
3RD SAMPLING ( 9/23/74)
3 SITES
RANGE MEAN MEDIAN
14.1 - 17.4 16.8 17.3
0.0 - 8.8 7.1 8.2
382. - 389. 385. 386.
6Q — Q 1 t A on
• 7
218.
0.046
0.017
0.020
0.020
0.800
0.040
0.820
6.8
2.1
— O» A
OT^
• 276*
~ 0*422
• 0*389
- 0*020
- 2.230
* 3*200
y 3cn
~ C.C3U
- 3.220
- 10.7
2.6
r . ^
0^1
231.
0.096
0.048
0.020
0.290
1.173
0.310
1.193
8.1
2.4
O. V
226.
0.052
0.024
0.020
0.040
0.900
0 .060
0.920
6.9
2.4
-------
B. Biological characteristics:
1. Phytoplankton -
Sampling
Date
04/22/74
07/09/74
09/23/74
2. Chlorophyll a_ -
Sampling
Date
04/22/74
07/09/74
09/23/74
Dominant
Genera
1.
2.
3.
4.
5.
1.
2.
3.
4.
5.
1.
2.
3.
4.
5.
Cyclotella sp.
Fragilaria sp.
Flagellates
Melosira sp.
Peridinium sp.
Other genera
Total
Flagellates
Aphanocapsa sp.
Aphanizomenon sp.
Fragil aria sp.
Schroederia sp.
Other genera
Total
Oocystis sp.
Sphaerqcystis sp.
Microcystis sp.
Flagellates
Melosira sp.
Other genera
Algal Units
per ml
1
395
930
465
62
31
155
Total
Station
Number
1
2
3
1
2
3
1
2
3
3,038
642
471
285
157
71
271
1,897
164
144
144
123
82
205
862
Chlorophyll a
(yg/D
5.1
5.1
6.8
6.3
7.4
14.4
6.8
6.9
10.7
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C. Limiting Nutrient Study:
1. Autoclaved, filtered, and nutrient spiked -
a. April sample -
Spike (mg/1)
Control
0.050 P
0.050 P + 1.0 N
1.0 N
b. September sample -
Ortho P
Cone, (mg/1)
Inorganic N Maximum yield
Cone" (mg/1) (mg/1-dry wt.)
0.005
0.055
0.055
0.005
0.072
0.072
1.072
1.072
0.1
1.0
25.1
0.1
Spike (mg/1)
Control
0.050 P
0.050 P + 1.0 N
1.0 N
Ortho P
Cone, (mg/1)
0.075
0.125
0.125
0.075
Inorganic N Maximum yield
Cone, (mg/1) (mg/1-dry wt.)
0.272
0.272
1.272
1.272
3.8
4.0
15.5
10.3
2. Discussion -
The control yields of the assay alga, Selenastrum capri-
cornutum, indicate that the potential primary productivity
of West Okoboji Lake was low in April but moderately high
in September, 1974. In the April assay, a significant
increase in yield occurred with the addition of phosphorus
alone but not with the addition of only nitrogen. In the
September assay, a significant increase in yield occurred with
the addition of nitrogen alone but not with the addition of
only phosphorus. Thus, phosphorus limitation is indicated in
the April sample, and nitrogen limitation is indicated in the
September sample.
The lake data substantiate these findings. In April, the
mean inorganic nitrogen to orthophosphorus ratio was 14 to 1,
and in September it was 6 to 1.
-------
8
V. LITERATURE REVIEWED
Anonymous, 1974. Management plan for water quality - Iowa Great
Lakes. Eugene A. Hickok and Associates, Wayzata, Minnesota.
Bachmann, Roger W., and John R. Jones, 1974. Water quality in the
Iowa Great Lakes. MS, Dept. Zoo. & Ent., IA St. U., Ames.
Harrison, Harry M., 1975. Personal communication (lake morphometry).
IA Cons. Comm., Des Moines.
-------
VI. APPENDICES
APPENDIX A
LAKE RANKINGS
-------
LAKE DATA TO BE USED IN
LAKE
CODE LAKE NAME
1901 LAKE ACOUAdI
1902 BIG CREEK RESERVOIR
1903 BLACK HAWK LAKE
190* CLEAR LAKE
1905 LAKE DARLING
1906 LOST ISLAND LAKE
1907 LAKE MACBRIDE
1908 PRAIRIE ROSE LAKE
1909 RATHBUN RESERVOIR
1910 RED ROCK LAKE
1911 ROCK CREEK LAKE
1912 SILVER LAKE
1913 SPIRIT LAKE
191* VIKING LAKE
1915 WEST LAKE OKOBOJI
MEDIAN
TOTAL H
0.06?
0.0*6
0.185
0.059
0.077
0.1*6
0.061
0.056
0.071
0.180
0.065
0.193
0.0*1
0.075
0.0*6
MEDIAN
INO«G N
0.3J5
6.*65
0.130
0.070
l.*75
0.065
2.035
0.210
1.170
1.880
l.*00
0.565
0.090
0.130
0.060
500-
MEAN SEC
*6V.333
*36.500
*88.167
*65.125
*S2.500
*21.167
*58.***
463.667
*75.889
473. *00
*80.500
*82.667
*22.667
*59.000
380.***
MEAN
CHLOHA
8.600
16.867
*9.7*0
17.*00
13.817
36.100
17.067
17.350
12.039
I*. 730
18.367
95.300
12.622
26.033
7.722
15-
MIN DO
8.200
i*.8oo
15.000
8.600
9.200
8.400
15.000
8.600
14.000
1*.000
8.400
10.000
9.000
14.200
15.000
MEDIAN
OISS OKTnO P
0.009
0.011
0.020
0.010
0.012
0.021
0.010
0.010
0.008
0.10*
Oo007
0.03*
0.007
0.017
0.017
-------
PERCENT OF LAKES WITH HIGHER VALUES (NUMBER OF LAKES WITH HIGHER VALUES)
LAKE
CODE LAKE NAME
1901 LAKE ACOUAdI
1902 BIG CREEK RESERVOIR
1903 BLACK HAWK LAKE
1904 CLEAR LAKE
1905 LAKE OAPLING
1906 LOST ISLAND LAKE
1907 LAKE MftCBRIDE
1908 PRAIRIE ROSE LAKE
1909 RATHBUN RESERVOIR
1910 RED ROCK LAKE
1911 ROCK CREEK LAKE
1912 SILVER LAKE
1913 SPIRIT LAKE
1914 VIKING LAKE
1915 WEST LAKE OKoaoJi
MEDIAN
TOTAL P
57
89
7
71
39
21
64
79
43
14
50
0
100
36
89
( 8)
( 12)
( 1)
( 10)
( 4)
( 3)
( 9)
( 11)
( 6)
( 2)
( 7)
( 0)
( 14)
( 5)
( 12)
MEDIAN
INO*G N
50 (
0 (
68 (
86 (
21 (
93 <
7 (
57 (
36 (
14 (
29 (
43 (
79 (
68 <
100 (
7)
0)
9)
12)
3)
13)
1)
8)
5)
2>
4)
6)
11)
9)
14)
500-
MEAN SEC
43 (
79 (
0 (
SO (
14 (
93 (
71 (
S7 (
29 (
36 (
21 (
7 (
86 (
64 (
100 <
6)
11)
0)
7)
2)
13)
10)
8)
4)
5)
3)
1)
12)
9)
14)
MEAN
CHLORA
93 (
57 (
7 (
36 (
71 (
1* (
50 <
43 (
86 (
64 (
29 (
0 (
79 (
21 (
100 (
13)
8)
1)
5)
10)
2)
7)
6)
12)
9)
4)
0)
11)
3)
14)
15-
MIN DO
100 I
21 <
7 (
75 t
57 (
89 (
7 (
75 (
39 (
39 (
89 (
50 (
64 (
29 (
7 (
14)
3)
0)
10)
8)
12)
0)
10)
5)
5)
12)
7)
9)
4)
0)
MEDIAN
DISS ORTHO P
79 (
50 (
21 (
64 (
43 (
14 (
64 (
64 (
86 (
0 (
96 (
7 (
96 (
32 (
32 «
11)
7)
3)
8)
6)
2)
8)
8)
12)
0)
13)
1)
13)
4)
4)
INDEX
NO
422
296
110
382
235
32<*
263
375
319
167
314
107
504
250
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 OK080JI 428
3 1901 LAKE ACOUA8I 422
4 1904 CLEAR LAKE 382
5 1908 PRAIRIE 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
11 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 107
-------
APPENDIX B
CONVERSION FACTORS
-------
CONVERSION FACTORS
Hectares x 2.471 = acres
Kilometers x 0.6214 = miles
Meters x 3.281 = feet
-4
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 = Ibs/square mile
-------
APPENDIX C
PHYSICAL and CHEMICAL DATA
-------
STORET RETRIEVAL DATE 76/03/11
191501
43 22 35.0 095 09 35.0 3
WEST LAKE OKOBOJI
19 IOWA
DATE
FROM
TO
74/04/22
74/07/09
74/09/33
TIME
OF
DAT
13
13
13
13
14
14
14
14
14
14
11
11
11
11
DEPTH
00010
WATER
00300
00
TEMP
30
30
30
30
10
10
10
10
10
10
20
20
20
30
FEET
0000
0005
0015
0023
0000
0005
0015
0030
0045
0060
0000
0005
0017
0035
CENT
6.8
6.8
6.6
6.8
22.5
32.6
22.5
22.0
18.7
16.6
17.4
17.3
17.3
17.3
00665
DATt
FROM
TO
74/04/32
7
-------
STORET RETRIEVAL DATE 75/13/33
191502
43 21 37.0 095 08
WEST LAKE OKOBOJI
19059 10*A
DATE
FROM
TO
74/04/22
74/07/09
74/09/23
DATE
FROM
TO
74/04/22
74/07/09
74/09/23
TIME DEPTH
OF
DAY FEET
15 00 0000
15 00 0005
15 00 0025
15 00 0050
15 00 0070
13 30 0000
13 30 0005
13 30 0015
13 30 0026
13 30 0050
13 30 0070
13 30 0090
13 30 0105
10 30 0000
10 30 0005
10 30 0025
10 30 0050
10 30 0080
10 30 0105
10 30 0130
TIME DEPTH
OF
DAY FEET
15 00 0000
15 00 0005
15 00 0025
IS 00 0050
15 00 0070
13 30 0000
13 30 0004
13 30 0028
10 30 0000
10 30 0005
10 30 0025
10 30 0050
10 30 0080
10 30 0105
10 30 0130
10 30 0134
00010
MATER
TEMP
CENT
6.9
6.9
6.9
6.9
6.9
23.2
23.2
23.1
22.8
17.4
16.0
13.4
12.8
17.4
17.4
17.4
17.4
17.3
14.3
14.1
00665
PHOS-TOT
MG/L P
0.033
0.033
0.031
0.034
0.040
0.046
0.051
0.050
0.058
0.071
0.318
0.422
00300
DO
MG/L
11.6
11.6
11.6
11.6
8.0
8.2
8.0
8.0
5.0
2.4
0.2
0.2
8.0
8.2
7.8
8.0
7.8
0.0
0.0
32217
CHLRPHYL
A
UG/L
5.1
7.4
6.9
00077 00094
TRANSP CNDUCTVY
SECCHI FIELD
INCHES MICROMHO
144 292
291
291
291
291
132 457
457
459
452
408
400
379
375
104 386
386
387
387
387
384
389
00031
INCDT LT
REMNING
PERCENT
50.0
1.0
11EPALES
3
00400 00410
PH T ALK
SU
8.
8.
8.
8.
8.
8.
7.
7.
a.
a.
8.
8.
8.
6.
6.
60
60
60
90
20
00
90
90
05
06
01
02
00
97
87
CAC03
MG/L
204
204
196
210
206
232
228
220
222
222
248
246
2111202
0075 FEET DEPTH
00610 00625 00630
NH3-N TOT KJEL N02&N03
TOTAL
MG/L
0.030
0.020
0.030
0.020
0.020
0.040
0.040
0.030
0.040
0.040
1.700
2.230
N
MG/L
1.000
0.900
1.000
0.800
0.900
0.900
1 . 100
0.800
0.800
0.900
2.300
3.200
N-TOTAL
MG/L
0.040
0.040
0.040
0.040
0.040
0.020K
0.020K
0.020K
0.020K
0.020K
0.020K
0.020K
00671
PHOS-DIS
ORTHO
MG/L P
0.004
0.004
0.004
0.004
0.005
0.024
0.023
0.025
0.027
0.032
0.017
0.389
K VALUE KNOrtN TO B£
LESS THAN INDICATED
-------
STORE! RETRIEVAL DATE 75/13/23
191503
43 24 52.0 095 10 28.0
WEST LAKE OKOBOJI
19059 IOWA
DATE
FROM
TO
74/04/22
74/07/09
74/09/23
TIME
OF
DAY
15 30
15 30
15 30
15 30
11 20
11 20
11 20
11 20
10 00
10 00
10 00
10 00
DEPTH
FEET
0000
0005
0025
0035
0000
0005
0019
0032
0000
0005
0015
0035
00010
WATER
TEMP
CENT
7.5
7.6
7.5
7.5
23.8
23.7
23.6
23.4
17.1
17.1
17.0
16.9
00300 00077 00094
00 TRANSP CNOOCTVY
SECCHI FIELD
MG/L INCHES MICROMHO
11.6
11.6
10.4
7.4
7.8
7.6
7.4
8.4
8.6
8.4
8.8
144
96
84
297
296
294
294
461
461
460
458
383
383
383
382
11EPALES
3
00400
PH
SU
8.60
8.50
8.50
8.60
8.14
8.15
8.12
8.13
00410
T ALK
CAC03
MG/L
200
212
200
200
226
220
236
218
2111202
0040
00610
NH3-N
TOTAL
MG/L
0.030
0.040
0.020
0.020
0.030
0.020K
0.020K
0.020K
FEET DEPTH
00625
TOT KJEL
N
MG/L
0.900
0.800
0.800
0.800
1.000
0.900
0.900
0.800
00630
N02&N03
N-TOTAL
MG/L
0.040
0.050
0.040
0.040
0.020K
0.020K
0.020K
0.020K
00671
PHOS-DIS
ORTHO
MG/L P
0.005
0.004
0.003
0.003
0.022
0.020
0.019
0.017
DATE
FROM
TO
74/04/22
74/07/09
74/09/23
00665 32217 00031
TIME DEPTH PHOS-TOT CHLRPHYL INCDT LT
OF A REMNING
DAY FEET
15
15
15
15
11
11
11
10
10
10
10
30
30
30
30
20
20
20
00
00
00
00
0000
0005
0025
0035
0000
0002
0019
0000
0005
0015
0035
MG/L P
0
0
0
0
0
0
0
0
.035
.037
.037
.035
.046
.052
.050
.049
UG/L PERCENT
6.8
14.4
50.0
1.0
10.7
K VALUE KNOWN TO tit
LESS THAN INDICATED
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