U.S. ENVIRONMENTAL PROTECTION AGENCY
NATIONAL EUTROPHICATION SURVEY
WORKING PAPER SERIES
AN APPROACH TO A RELATIVE
TROPHIC INDEX SYSTEM FOR
CLASSIFYING LAKES AND RESERVOIRS
WORKING PAPER NO. 24
A Preliminary Analysis of
National Eutrophication Survey Data
Collected During
the 1972 Sampling Period
PACIFIC NORTHWEST ENVIRONMENTAL RESEARCH LABORATORY
An Associate Laboratory of the
NATIONAL ENVIRONMENTAL RESEARCH CENTER - CORVALLIS, OREGON
and
NATIONAL ENVIRONMENTAL RESEARCH CENTER - LAS VEGAS, NEVADA
•£ GPO 697-O32
-------
AN APPROACH TO A RELATIVE
TROPHIC INDEX SYSTEM. FOR
CLASSIFYING LAKES AND RESERVOIRS
WORKING PAPER NO. 24
A Preliminary Analysis of
National Eutrophication Survey Data
Collected During
the 1972 Sampling Period
National Eutrophication Survey
Pacific Northwest Environmental Research Laboratory
Corvallis, Oregon
December, 1974
-------
E 0 R. W A R D.
The Trophic State Index discussed in this report is not proposed
as the final answer to determining the trophic condition of lakes
and reservoirs; and there were, in fact, some reservations by the
Survey staff about making this paper available for public distribution.
The method described herein, however, has been useful to the Survey
for categorizing each water body according to trophic condition and is
therefore offered for whatever value it might have to others interested
in evaluating trophic conditions of lakes and reservoirs.
-------
INTRODUCTION
One of the major tasks confronting the staff of the National Eutro-
phication Survey is the assessment of the trophic condition of the water
bodies studied. Many of these waters previously have been studied only
superficially, if at all, and the Survey data provide the only basis for
the evaluation of trophic condition.
In addition, Section 314(a) of Public Law 92-500 requires that each
State classify, according to trophic condition, each of its publicly
owned waters. The question, of course, is which classification system
or index system to use. The Environmental Protection Agency (EPA) also
wants an index or indices which can be used to evaluate changes in water
quality over a period of time to determine whether conditions have im-
proved or deteriorated.
Therefore, from the beginning of the Survey, it was apparent that
there was a need for a lake classification system, based on Survey data,
from which the trophic condition of the Survey lakes could be better
defined and which also had some utility to the States in classifying other
lakes not included in the Survey.
The intent of the approach used by the Survey is to provide a numeri-
cal trophic index which will permit a more realistic assignment of trophic
condition then the relatively inflexible categorizations of oligotrophic,
mesotrophic, eutrophic, or hypereutrophic. It is apparent, particularly
when working with a large group of lakes, that trophic condition is a
-------
continuum with no sharp demarcations as are suggested by the traditional
classes and the trophic index utilized in this paper demonstrates that.
INDEX DEVELOPMENT
The development of an index or lake classification system is not a
new consideration in the limnological community. In perusing the liter-
ature, it quickly becomes evident that "the most striking feature of
limnological classifications is not the difficulty of producing some
sort of arrangement, but the multiplicity of arrangements that have been
proposed" (Sheldon, 1972). However, guided by a desire to devise a method
that could be used by those with little or no knowledge of the more com-
plex and sophisticated tools of statistical analyses (for some of which
large-scale computer capability is a necessity), our first effort was a
variation of a relatively simple ranking method used by Lueschow, et al.
(1970) for 12 Wisconsin lakes. Using the unweighted mean annual values
of selected physical, chemical and biological parameters— each of which
in one way or another reflect the trophic condition of a lake, Lueschow,
et al. derived a composite rating which was the sum of the numerical
values of position for each of the five parameters used (e.g., a value of
one was given for the lake with the greatest transparency, two for the
lake with the next greatest transparency, and so on), so the lake with
the lowest composite value was judged the most oligotrophic, and the lake
with the highest composite value was judged the most eutrophic.
-------
The Survey data base was much larger than that of the Wisconsin
study, however, and involved more than 200 lakes surveyed in 1972 for
the present assessment. Before the Survey is complete, another 500
lakes will be included for a total data base of 700+ lakes in which nine
usable water quality parameters were measured. This data base includes
the range of trophic conditions from some of the most pristine lakes
and reservoirs in the United States to some of the most eutrophic and,
therefore, will provide an excellent "relative" classification system
which could be used to determine the trophic condition of any lake not
in the original sample of 700 lakes (~200 treated in this report).
Rather than the positional ranking used by Lueschow, et al., a
percent!le ranking procedure was used. In this procedure, for each of
the unweighted parameters used, the percentage of the 200+ lakes ex-
ceeding Lake X in that parameter, e.g. level of chlorophyll a^, was
determined. The final ranking value or index number is simply the sum
of the percentile ranks for each of the parameters used (the values
for Secchi disc transparency and minimum dissolved oxygen are subtracted
from fixed values so that all parameters contribute in a positive way to
the ranking).
To test the merits of what might at least be a theoretical objection
to the use of correlated parameters, such as chlorophyll a_ and phosphorus
or chlorophyll a_ and Secchi disc transparency, percentile rankings were
determined with various combinations of the nine most pertinent parameters
-------
(a tabulation of seven non-weighted parameter combinations and resulting
rankings by the percentile method and two non-weighted parameter combina-
tions and resulting rankings by multivariate analysis is appended to
this report). Two of the combinations, one with six parameters and the
other with seven, appear to provide the best fit (with two kinds of
exceptions as noted below), and both combinations include correlated
parameters*.
Fortunately, a judgment of fit could be made with a degree of con-
fidence because a number of the 1972 lakes previously had been studied
by others, and the trophic condition of these lakes was generally agreed
upon. Among these "bench-mark" lakes were Lake Zoar, Connecticut; Sebasti-
cook Lake, Maine; Houghton and Higgins lakes, Michigan; Minnetonka and
Shagawa lakes, Minnesota; Lake Winnipesaukee, New Hampshire; the Finger
Lakes, New York; Lake Memphremagog, Vermont; and Geneva, Green, Kegonsa,
and Shawano lakes in Wisconsin.
Table 1, 2, and 3 provide an example of how the percentile ranking
system is used to develop an index. Nine Maine lakes, studied in 1972,
provide the data base in this example.
The six parameters (Table 1) which are used in combination to arrive
at an index number (Table 3), were those which seemed to provide the best
* The six-parameter ranking included the median total phosphorus, dissolved
phosphorus, and inorganic nitrogen; the mean chlorophyll a_; 500 minus the
mean Secchi depth; and 15 minus the minimum dissolved oxygen. The algal
assay control yield was added in the seven parameter ranking. Respec-
tively, these are combinations #1 and #2 in the appended tabulation.
-------
TABLE 1
Values of the Six Parameters Used in Developing a
Trophic Index Based Only on a Data Base of Nine Maine Lakes
Lake
Code
2304
2306
2308
2309
2310
2311
2312
2313
2314
Lake Name
Estes Lake
Long Lake
Mattawamkeag Lake
Moosehead Lake
Rangeley Lake
Sebago Lake
Sebasticook Lake
Long Lake
Bay of Naples
Median
Total P
(mg/1)
O.C94
0.008
0.011
0.005
0.007
0.004
0.050
0.010
0.005
Median
Inorg N
(mg/1)
0.230
0.080
0.120
0.180
0.110
0.155
0.110
0.200
0.070
500-
Mean Sec
(inches)
459
365
438
351
352
301
456
396
374
Mean
Chlorophyll a
(yg/1)
28.3
3.2
2.0
1.5
2.4
1.5
49.5
6.9
1.8
15-
Min DO
N/l)
12.8
9.2
11.6
7.6
7.8
6.4
9.0
9.0
6.6
Median
Diss P
(mg/1)
0.057
0.006
0.007
0.003
0.005
0.003
0.024
0.006
0.003
-------
TABLE 2
Percent of Maine Lakes Exceeding Parameter Value of Each Lake and the Trophic
Index Number of Each Maine Lake Using A Data Base of Nine Lakes
Lake
Code
2304
2306
2308
2309
2310
2311
2312
2313
2314
Lake Name
Estes Lake
Long Lake
Mattawamkeag Lake
Moosehead Lake
Rangeley Lake
Sebago Lake
Sebasticook Lake
Long Lake
Bay of Naples
Median
Total P
(mg/1)
0
44
22
77
55
88
11
33
66
Median
Inorg N
(mg/1 )
0,
77
44
22
55
33
55
11
88
500-
Mean Sec
(inches)
0
55
22
77
66
88
11
33
44
Mean
Chlorophyll a
(yg/i)
n
33
55
88
44
77
0
22
66
15-
Min DO
0
22
11
66
55
88
33
33
77
Median
Diss P
(mg/1 )
0
33
22
66
55
77
11
33
77
Index No.
(Sum of
Percentages)
n
264
176
396
330
451
121
165
418
-------
TABLE 3
Trophic Index Number and Trophic Condition of Each
Surveyed Maine Lake Using Data Base of Nine Lakes
Lake Lake Trophic
Rank Code Name Index No. Condition
1 2311 Sebago Lake 451 0
2 2314 Bay of Maples 418 0
3 2309 Moosehead Lake 396 0
4 2310 Rangeley Lake 330 0
5 2306 Long Lake 264 M
6 2308 Mattawamkeag Lake 176 M
7 2313 Long Lake 165 M
8 2312 Sebasticook Lake 121 E
9 2304 Estes Lake 11 HE
0 - oligotrophic
M - mesotrophic
E - eutrophic
HE - hypereutrophic
-------
separation of trophic condition when applied to the entire group of 209
lakes.
Table 1 simply depicts the values of each parameter for the nine Maine
lakes. Table 2 represents, for each parameter, the percent of lakes in
the data base (9 lakes) which exceed the parameter level for the lake
of interest. The last column in the table is the trophic index number
which is the sum of the percent!les for each parameter.
Using the data base of only 9 lakes, the highest percentile which
can be achieved for any parameter is 88 (8/9); therefore the highest
possible index number is 528 (6x88). In Table 3 the nine Maine lakes
are arrayed in order of their trophic index number from most oligotrophic
to the most eutrophic lake and also classified according to the traditional
system of oligo-, meso-, eutrophic, or hypereutrophic.
The example of the nine Maine lakes does not include either of the
two kinds of exceptions to the good fit of rankings referred to on page
3. The two exceptions are (1) water bodies with very short hydraulic
retention times (less than five days) and (2) water bodies characterized
by extensive littoral zones, and excessive production of macrophytes. In
the first case, the essentially "flow-through" hydraulic regimes result in
flushing of nutrients, and nutrient concentrations may remain relatively
low in spite of loading rates that frequently are very high. In the
second case, the macrophytes may compete effectively with algae for the
available nutrients with the result that nutrient levels frequently are
-------
low, chlorophyll levels are low (because algal populations are low), and
Secchi disc values may be relatively high (possibly a combination of
fewer algae and the enhancement of sedimentation of particulate matter
in the relatively quiet waters provided by the weed beds).
While the mean hydraulic retention time can be quantified and used
as a parameter in ranking if it is known, the volumes of many of the 1972
Survey study waters are not known, and the retention times cannot be
determined. Likewise, if macrophyte populations could be conveniently
quantified, this parameter could also be used in ranking the waters.
The same procedures explained above for the nine Maine lakes were
applied to all of the lakes surveyed in 1972 representing a data base
of 209 water bodies of many different trophic conditions. With this
data set, the highest index number which could be achieved would be 594
(99 x 6) which would represent the most oligotrophic lake and the lowest
index number which could be achieved would be 0, representing the most
eutrophic lake.
Table 4 lists the 209 lakes ranked in order from best to worst tro-
phic condition according to the index numbers and also indicates the
trophic state nomenclature (oligotrophic, mesotrophic, or eutrophic) which
is believed to typify each water body.
In general, the conclusion can be drawn from Table 4 that those lakes
with a trophic index number of 500-600 correspond to a very good trophic
condition and are oligotrophic with the transitional range to mesotrophic
beginning in the 500-525 range.
-------
10
TABLE 4
RANK
1
2
3
it
5
*
7
H
9
10
1 1
»?
13
14
IS
Ifc
17
1«
19
20
2}
22
23
2^
?5
26
27
2«
LAKE CODE
2314
2311
3303
5571
?*>ys
PJO1^
?310
3
-------
*AN*
29
30
3)
3?
33
~\<*
35
3*
37
3«
30
40
4J
42
43
44
45
46
47
48
49
50
51
5?
53
54
55
5*
LAKt COOF.
? /«?
2 'JO*
363'
2*96
27H*
5004
5'JO?**
36?7
PJA-*
3*C>H*
5S60*
50 1 0 **
?73U
274^,
5Sft3*
?(S10**
5539*
S^S1^*
2710
553<>*
553?*
5519
3*>36
55«S9*
3306**
3610
3615
267?**
!
LAKE NAME
U^EEN LAKt
MATTAWAMKtfAG LAKE
SACA^JDAGA ^tSERVOIP
HOUGHTON LAKE
LA*,K CAPLOS
LAKE M£MPnrttMAr>Ofi
LAMOILLE LAKE
ODA.SCO LAKE
S'VA'i LAKE
LAKE CAYUfiA
H^OWMS LAKE
LAKE A»PO«HtAO
F"ALL LAKE
LEECH LAKE
LAC LA BELLE
^ETSIE LAKE
SHiUANO LAKE
CONESUS LAKE
BI^CH LAKE
^INE LAKE
.OCONOMOwOC LAKE
G*EEN LAKE
SWAN LAKE
MIDDLE LAKE
KELLr FALLS POND
CHAUTAOUUA LAKE
HUNriNGTON LAKE
«OGE«S PQMD
1 |
TABLE 4
_(Page_2)_
INOEX NO
451
449
444
443
441
43H
433
431
*31
• 4?6
• i
4?5
4?5
4?5
4?2
419
419
418
418
416
412
403
403
403
397
393
391
390
387
„
TROPHIC CONDITION
M
M
M
M
M
E
M-E
M
M
E
E
M
M
E
E
E
E
E
E
E
M
E
M-E
E
E
E
E
-------
TABLE 4
_ . . - ... __ . (Paae 3)
SANK LAKE CODE
57 5001
SK 330?**
60 3633
6? ?7M
63 2674**
6<* 5S66
65 3*0?
66 ?793
67 ?h49 **
6« 2715
69 ?7AS>*
70 ?737
71 ?7HS
7? 3640
73 2745
74 36?5
75 3613
76 2751
77 5574
78 27C1
79 2711
80 4402**
81 2698
A3 O^. Q Q
83 2618
84' 090?
LAKE NAME INDtX NO
CH4MPLAIN LAKE
POVDE-? MILL POND
DARLING LAKE
SARATOGA LAKE
OK^i'CHFE LAKE
MINNtWASKA LAKE
SANFOi^O LAKE
^O'J'-.'O LAKE
-
-------
_ 13
RANK
<*s
36
fl7
8H
«9
QU
2685
2621
26«0
0904
5551
3610
2697
5562
2747
COOF LAKE NftME
iU-FGHENY RtSEKVOIR
PELICAN L-JKt
ROSS ->ESF^VUIR
Ca^SADAOA LAKE
ANOrtUSIA LAKE
PEWAUKEE LAKE
PLENiM LAKE
SHc.LTorg LAMi
LAKF ..^ISSOTA
FLK LAKE
HOCriDiLE POND
CLEAKWATE9 LAKE
S1AGAWA LAKE
NEST LAKE
SEdASTICOOK LAKE
LONG LAKE
WAPOGASSET LAKE
YELLO.V LAKE
8LACKHOOF LAKE
UM10N LAKE
CONSTANTINE KESEftVOIR
HOLLOVnAY RESERVOIR
EAGLEVILLE LAKE
LAKE rfA'JSAU
•JOIIMO LAKE
THOMPSON LAKE
LAKE COMO
ST CKOIX LAKE
TABLE 4
.(Page 4) ...
INDEX N0~~
330
330
330
32B
32«
327
327
3?5
324
3C3
303
300
?97
293
293
292
291
286
279
279
273
271
271
266
266
266
265
264
"TROPHIC CONDITION
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
-------
14
RANK
m
114
us
11*
117
11^
119
120
1?1
1??
123
i?4
125
12*
127
138
1?9
130
131
13?
133
134
135
13*
137
138
139
140
LAKE. CODE
S57H
27?0
?665
27A2
0-H1
?7i»O
SSO^
550*
2633
5535
0°10
27Ai
27?S
2*9^
2760
2643
26S9
2692
553b
27P^
2513
2756
5S^^*
5546
27Bh
S5?0
3637
?70^
L-'V*';- MA.Mf
ST CPOIX LA<£
C^aNHT^Pr LAKE
PENT.vaTEP LAKE
•iQLf-" LAKE
L ILL I MO AH LAKF
WHITE c.'aTE^ LftKK
aiJTrf^fxIMl LJ<\E
HUTTE. Q£S M(MJ"7
Ti-tOHMAPPL^ LAKi-:
PIGEO'J LAKE
ZOA-^ LAKf
•VI MOM fl LAKE
FLHOW LAKE
ST^AwBEPRr LAKP
LAKE MINNETONK.A
KfNT LAKE
MUSKEGON LAKE
LOi-KJ LAKE
POYGAN LAKE
SUPERIOR HAY
HUDSON IMPOUNDMENT
MASMKENODE LAKE
TOmliM LINE LAKE
TAINTED LAKE
CALHOUN LAKF
KEGONSA LAKE
SWINGING PHI DOE RESERVOI
HIG STONE LAKE
TABLE 4
(Page 5)
INOFA NO
26?
26?
259
?SH
?5H
^S7
?S6
254
'54
' 247,
?46
?4b
?44
243
241
?37
231
230
229
2?9
225
223
21H
216
216
214
214
213
TROPHIC CONDITION
E
F
E
E
E
E
E
F
E
E
F
E
E
E
E
E
F,
E
E
F
E
E
F
E
E
£
E
E
-------
15
3ANK
]<*!
142
143
144
14*
I**?
L_4»
14"
150
151
15?
• 153
154
155
156
157
1SB
159
160
161
16?
163
16*
165
166
167
16*
LAKK COOP
^777
5S«1
2*93
2 70S
ssn?
ss:u
?792
._?.5U
?SO 1
?.<04
2h71
?731
5f i'J
2*A1
5SAS
?7^«
5503
5534
0901
?7C3
?'»0C»
2796
?M3
0905
5522
2752
5555
271*
LAKE :^A^E
aAKATA-l LAKt
SlJPf.^ru^ 8A1T
ST LOUIS hft^ERVOIR
bAWTLLTT LAKE
ALTOONA LAKt
LAiv?; 'JA'--A»1CKA
T&ACE LAKE .
HILLEWICA IMPOUNOMENT
HA^yPlS PONO
ESTES LAKE
PANOALL LAKE
FANNY LAKf":
CASTLE »OCK FLOWAGE
Cfl.HO RESERVOIR
SWAN LAKE
LITTLE LAKE
aEAVt'O DAM LAKE
PETENWELL FLOWAGE
ASPINOOK LAKE
COTTONWOOD LAKE
BELLEVILLE LAKE
TUTTLE LAKE
ri^IrtriTON LAKE
MA'v'OVER PONO
KOSHKOMONG LAKE
MALMtOAL LAKE
WISCONSIN LAKE
COKATO LAKE
TABLE 4
(Page 6)
INDEX NO
211
209
20"
20*
?07
205
205
?04
203
201
199
196
193
193
191
191
189
186
186
182
181
IPO
180
178
176
176
174
171
TROPHIC CONDITION
E
E
E
E
E
E
E
E
E
E
E
E
E
e
E
E
E
E
E
P
E
E
E
E
E
E
E
E
-------
16
TABLE 4
" RANK LAKE CODE LAKE NAME INDEX NO TROPHIC CONDITION
1*>Q 5554
170 ?/VA
171 3M1
172 5513
173 2753
1 7*. ?Sf)7
175 2750
176 ?504
177 2706
178 556S
1 79 26?'-*
130 ?606
IB. 27A4
1H2 5SH?
1R3 5515
184 ?7A6
18h 2508
187 27B8
138 2640
189 5570
190 27A8
191 36 Ib
192 27A5
193 55P3
194 2648
195 27R1
19fc 2713
ST LOUIS 84f
CPOSS LAKE
LAKE OELAVAM
MUO LAKE AT MAPLE LAKE
WOODS PONiJ
MADISON LSKE
•MAYMAPU IMPOUNDMENT
•^EA^ LAKE
61'3 EAU PLEINE SESE.RWOIR
FO^O LAKE
HA^TON LAK--;
LAKE PEPIN
LAKE P£P1N
EA'I CLAIRE LAKE
SPRING LAKE
ALLEGAN LAKE
MATTFIELD IMPOUNDMENT
LOST LAKE
JORDAN LAKE
GRAND LAKE
HUOO LAKE
IRONDEiJUOIT BAY
ZtJMfeHO LAKE
ST LOUIS BAY
LAKE MACATArtA
WAGONGA LAKE
BUFFALO LAKE
170
167
165
16?
161
160
159
158
155
150
146
144
141
139
138
137
134
133
132
130
128
126
125
123
122
118
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
F
E
E
HE
-------
SANK LflKC COOE"
157 2*91
198 273?
199 0<)03
?00 270?
2Q1 27C2
?0? 271*
203 2SO£
204 ?78b
205 4403
20ft 2*31
?U7 5SS9
203 27A3
?39 27M7
0 01 igotrophic
M - Mesotrophic
E - Eutrophic
*.- Weeds
— ** <^ww>aii1 i
LAKt NAME
WON A L/**E
SILVER LAKE
COMMUNITY LAKIi
ALSEf LAKE
Tu^^trf SESEKVOIR
Fr^FMOMT LAKE
TICHIGAN LAKE
'VOOUCOCK LAKE
WALLMAHK LAKE
p — Qat'cmt'-iroi — T-iroa
TABLE 4
... _(Page 8}
INDEX NO
I
lift
114
112
10?
100
9V
94
t)3
9?
9? >
80
60
41
TROPHIC CONDITION
HE
HE
HE
HE
UP
HE
HE
up
HE
HE
UP
HE
HE
-------
18
Lakes with a trophic index of 420-499 are those which would ordi-
narily be classed mesotrophic and below 420 the lakes become progres-
sively more eutrophic. The 300-419 range of the index represents lakes
which are eutrophic and have occasional nuisance algal problems but still
may support excellent fisheries. Below 300, nuisance conditions may be
expected more frequently; however, even some of these lakes may be
expected to support good fish populations.
The reader should understand that the index number ranges mentioned
above, which correspond to the various trophic states, are only valid
when used with the data base of 209 lakes and reservoirs considered in
this report. If a different data base were used, for example, one con-
taining a higher percentage of high quality lakes, the resulting index
number might be interpreted quite differently, e.g. oligotrophic rather
than eutrophic.
As discussed earlier, all lakes and reservoirs sampled in 1972 were
included in this index regardless of morphometry or detention time.
Therefore, lakes with relatively low trophic index numbers may have the
apparent potential for developing nuisance conditions but may not do so
because of extremely short flow-through times.
It is of interest to evaluate the proposed index in terms of lakes
and reservoirs with known nuisance levels of algae. Such an evaluation
was made with water bodies listed in "Problem Lakes of the United States"
-------
19
which was compiled by Ketelle and Uttormark (1971) of the University of
Wisconsin Water Resources Center. In Table 5, lakes which were cited
in the aforementioned publication and were also included in the Survey
are listed by State and the Trophic Index Number for each lake is also
given.
The data in Table 5 substantiate that for overall lake quality, the
trophic index does differentiate the high quality lakes from those which
have the potential of developing nuisance conditions. If a specific lake
were beginning to exhibit signs of eutrophication along shoreline areas
or in bays, the index would not show the localized degradation unless
the lake was specifically sampled in the worst areas. This characteris-
tic would, however, be a weakness in any simple trophic index system.
While the major Survey effort in ranking of lakes has been with the
percent!le method outlined above, the more sophisticated methods of
statistical analysis have also been examined. Thus far, Survey data have
been subjected to the multivariate analysis recently recommended by
Harkins (1974), and Don A. Pierce, Associate Professor of Statistics
at Oregon State University, has employed a discriminate function anal-
ysis. Also, Dale H. P. Boland, a doctoral candidate at Oregon State
University, who is investigating the feasibility of estimating the tro-
phic status of inland lakes through the use of the Earth Resources
Technology Satellite (ERTS-1) multispectral scanner and is using the
ground-truth data of 100 of the 1972 Survey lakes (see Working Paper
-------
20
TABLE 5
Trophic Index Numbers for Lake and Reservoirs Cited
in "Problem Lakes, of the United States" and Included
in the National Eutrophication Survey
State
Connecticut
Maine
Massachusetts
Michigan
Minnesota
New York
Wisconsin
Vermont
Lake Name
Bantam
Lillinoah
Zoar
Estes
Sebasticook
Hager Pond
Barton
Brighton
Betsie
Chemung
Ford
Fremont
Jordan
Kent
Macatawa
Manistee
Mona
Muskegon
Randall
White
Big Stone
Budd
Madison
Minnetonka
Shagawa
Sakatah
Cayuga
Cones us
Saratoga
Schroon
Seneca
Butternut
Butte Des Morts
Delavan
Koshkonong
Kegonsa
Nagawicka
Pewaukee
Poygon
Shawano
Tichigan
Winnebago
Champ!ain
Memphremagog
Trophic Index Number
332
258
246
201
293
94
150
180
419
334
155
92
133
237
123
365
118
231
199
334
213
130
161
241
297
211
426*
418
373
541*
482*
256
254
165
176
214
205
327
229
418**
80
170
385
439t
* Generally high quality lakes showing positive signs of deterioration.
** A naturally eutrophic lake with an aquatic macrophyte problem.
t An oligotrophic lake which has deteriorated in the south end due to
phosphorus inputs from U.S. point sources.
-------
21
No. 10), has subjected the data to principal component analysis and
cluster analysis. None of the complex analyses noted above provide a
better ranking of the lakes than the percentile method (some are not
as good), and all have the same failing as the percentile method with
respect to retention times and macrophytes.
TROPHIC INDEX USE
Using the data base of 209 lakes as presented or a larger base as
the data are produced by the Survey, it would be relatively easy to
determine the relative trophic condition of an unknown lake (Lake X)
by determining its trophic index number. Changes in the trophic condition
of Lake X could also be followed in the same manner by determining its
trophic index number each year and charting the improvements, deteriora-
tion, or status quo, whichever the case might be.
The data required to compute the trophic index would have to be for
the same parameters used in the index system presented above; i.e., (1)
total phosphorus, (2) dissolved phosphorus, (3) inorganic nitrogen, (4)
Secchi depth, (5) minimum dissolved oxygen (in the hypolimnion if strati-
fication occurs), and (6) chlorophyll a_. Each of the values used should
be means or medians for the entire lake or at least values which are
believed to be representative of the entire water body or that portion
which the investigator is interested in classifying.
After the data for the appropriate parameters had been gathered, the
percentile table (Table 6) would be used to determine for each parameter
the percent of lakes exceeding the value for the lake of interest. The
-------
TABLE 6
MEDIAN
TOTAL P
(mg/l)
0.0,1'.
0.004
O.OOS
o.nos
0.006
o.uof
0.007
d.i>i>7
O.JD8
0.008
O.OOH
0.008
0.009
0 .009
0.001
0.009
0.004
"0.009"
0.010
0.010
0.010
0.010
0.011
0.011
0.011
0.01?
PERCENT MEDIAN
HIGHER INORG N
(mg/D
99 0.060
99 0.060
9^ 0.07U
9H
97
97
IS
9S
93
13
93
93
10
90
90
90
PR
OR
8H
Hrt
H7
87
86
0.0/0
0.070
0.070
U.OMO
O.OMO
O.OHO
0.090
U.090
0.040
U.0"0
0.090
n.ioo
il. 100
0.100
0.100
0.110
o.iio
0.110
0.1?0
0.120
0.120
0.125
t.130
0.130
0.130
Parameter Val
Numbers for I
by thi
PERCENT 500-MEAI
HIGHER SECCHI
(Inches;
99 184.000
99 268. bOO
97 27'. 555
97
97
95
9S
93
93
93
93
93
91
"1
91
89
~H9
89
R»
88
8fl
88
Sh
86
2.3.667
300.933
3?3,?SO
338.000
34?. 875
3S1.04H
353.000
3S4.000
3S9.333
360. / 78
362.000
363.500
364.111
"365.333
366.333
373. 87S
374.000
374.500
380. BOO
3»3.833
385.333
385.364
lue Percentllns for Establishing Trophic !
Inclasslfled Lakes; Based. on 209 Lakes Sat
• National Eutrophlcation Survey in 1972
1 PERCENT MEAN CIILOR- PERCENT
HIGHER OPHYLL a HIGHER
1 (ug/D ~
99 1.043
99
98
9B
.97
97.
96
9h
95
95
94
94
• 9.1
9?
92
91
91
90
~ 90"
89
B9
8B
MB
88
87
87
86
1.46?
1.487
1.500
_..lU767
1.767
1.850
1.989
2.067
2.075
2.083
2.433
2.683
2.986
3.008
3.067
37067
3.1M9
3.236
3.467
3.533
3.540
3.783
3.810
4.333
99
99
98
97
9.7
96
96
95
9S
94
94
93
"93
9?
92
91
91
90
90
89
89
88
88
88
87
87
86
Index
roled
15-MlNIr-UH PERCENT
DO HIGHER
(rn/l )
4.HOO
5.300
6.200
6.300
6.400
6.600
6.600
6.600
7. 000
7.000
7.000
7.200
7.200
7.400
7.400
7.400
7.400
7.400
7.500
7.500
7.600
7.600
7.600
7.700
7.700
7.800
99
99
98
98
95
95
94
" "94
94
93
93
..90
90
90
90
90
89
89
"" 88"
88
88
87
87
84
MEDIAN DI5- PERCENT
SOLVED P HIGHER
(mg/l)
0.003 99
0.003 99
0.001 98
0.003 98
0.004 95
.0.004 95
0.00«. 95
0.004 9S
0.004 9b
0.005 92 fO
O.OOS 92
O.OOS 92
O.OOS 92
O.OOS 92
O.OOS 92
0.005 li
0.005 91
0.006 88
0.006 8h
0.006 48
0.006 88
0.006 MX
0.006 SB
0.006 88 . „ . . . _
0.006 Hb
0.007 85
0.007 <)5 . .
0.007
85
-------
TABLE 6
MEDIAN
TOTAL P
(mg/1)
0.313
0.011
0.013
O.UM
—° •?'.*„.
0.014
O.OIS
0.01ri
O.OIS
O.ulS
O.OIS
0.016
o.uis
0.017
0.017
O.OIH
0.01H
0.018
0.01"
0.019
O.O'O
o';o(?o "
0.0?(J
O.U/>1)
0.0^1
0.021
O.i)?l
o.o;v
PERCENT MEDIAN
HIGHER INORG N
(mg/D
H4 0.115
•<4 O.I IS
H4 0.135
H4
H4
83
HI
HI
HI
^1
Ml
HO
RO
79
74
77
77
77
7;
77
7S
' 75
7S
75
73
71
73
/'
0.140
0. 140
0.140
0.1".0
O.l'.O
0.140
0.140
0.145
u. ItS
0.145
O.l«5
0.145
0.1SO
0.1 ',0
0.1 SO
0.1 bO
0.150
O.lbS
0.1 SS
0.1*0
0. 160
0.160
0.170
0.170
0. I/O
. PERCENT
HIGHER
BS
H'i
8S
8?
H2
8?
fl?
S2
8?
HI
74
74
79
/>J
79
7fl
;«
77 •
77
77
7h
76
7S
7 . B
80
TI
77
77
77
77
77
77
77
76
73 "
73
73
73
.73
73
7J
-------
TABLE 6
(I'age 3)
MEDIAN PERCENT MEDIAN
TOTAL P HIGHER INORG N
(nig/1) (mg/1)
0.072
0 * 0 <*^*
o • u f*'*
" 0.075
u . J75
O.J76
O.U26
0.0?7
0.0 i>i>
0.07H
" 0.07H
_ 0.07H
0.07M .
O.OrM
. 0.079
0.010
O.OJ1
0.032
0.012
~ 0.0. 12
0.013
0.0. I*
7?
If
71 .
71
70
69
f.9
M
67'
*•?
f-f-
f.4
„<.
64
hi-
fi .)
63
61
6?
"*
60
hi)
60
su
O.lf5
0.175
0.175
0.1HO
O.IS5
0.1 90
._.. N • 1?0
0.190
0 . 190
0.195
0.200
0.200
O.?00
o.?oo
~0.205
n.?io
0.210
0.210
o.?in
0.2?0
0.220
0.210
0.230
0.7JO
O.'IO
0.^0
PERCENT
! HIGHER
72
72
U -
71
70
70
69
— —
«.
67
66
"66
66
65
63
63
63
6.3 ...
62
62 '
61
61
60"
60
500-MEAN
SECCHI
(Inches)
419.667
420.500
- 420.667
421.444
4??.. 000
421.500
424.000
424.500
4P4.800
425.000
4^5.667
475.8PI.9
476.000
476. H31
477.667
427.667
428.400
479,000
430.333 '"
430.667
410.750
430.800
412.167
4)7. J31
PERCENT
HIGHER
72
72
71
71
70
_ZO_
fSH
6b
67 .
67
66
66
66
65
'65
64
63
63
.63
62
62 "
61
61
60
59
MEAN CHLOR- PERCENT 15-MIHIMUM PERCENT MEDIAN OIS-
OPHYU a HIGHER 00 HIGHER SOLVED P
(U9/1)~ (ng/1) (mg/1)
7.044
7,050
7.133
7.186
7.233
7.450
7.500
7.500
7.622
7.933
8.100
8.133
8.133
8.1H3
H...350
8.483
"87533
8.6H9
9.167
9.211
9.217_
9.467
9.483
9.511
9.633
9.700
9.783
9. BOO
72
72
Jl
71
70
70
64
69
68
68
67
67
66
66
66
65
65
64
64
63
63___
62
62 ~
61
61
60
60
59
8.600
B.660
-fi.TOO
8.760
8. 800
8.900
8.900
8.900
9.000
9.000
9.000
9.000
9.000
9.000
9.000 .
9.000
9.200
9.200
9.200
9.200,
9.200
"9.200
9.240
9.240
9.400
9.500 .
9.520
72
72
71
71
70
69
65
65
65
65
65
65
_ 65 .. ...
65
62
62
™ 62
.62.
62
" 62"
61
61
60
60
59
0.011
0.011
0.011
0.011
o.oii
0.011
0.017
6.012
0.012
0.013
0.013
-0.013
0.013
0.01J
0.014
0.014
O.OlV"""
0.014
0.014
0.014
0.015
0.015
0.015
_0.015
0.016
0.016
0.016 ..
0.017
PERCENT
HIGHER
70
70 . ""
70
70
70
70 .... '..
61
66 JVJ
66
66
66
66
«
63
"63
63
63
61 . .
i'
61
61 ....
60
60
.60 . ... ..
58
-------
MEDIAN
TOTAL P
(rag/1)
0.0.14
0.0 I1)
0.015
O.d.lh
0.0. "H
0.839
o.o 39
0.0<.J
0.041
o.a<4^
O.J«. 1
O.O-O
0.0-.3
O.U43
0.0<>3
o.o<.3
O.U43
o.n<.3
O.IK4
0.044
0.0"S
n.o<.7
0.047
0.04P
0.048
0.0*9
0.04^
0.050
PERCENT
HIGHER
50
SH
5*
s;
S7
S6
S*
ss
55
ss
53
S3
S3
S3
51
SI
SI
SI
60
f.0
49
<4H
AH
<>H
47
47
<<6
45
0
MEDIAN
INORG N
(mg/1)
o.?-«n
O.PtO
O-PftO
O.^'.O
O.?40
o.?so
O.PS5
l).?60
O.?60
O.PhO
0.370
0.//0
O'.2'0
0.870
O.P70
o.?^n
0.
-------
TABLE 6 ._._..._..._
MEDIAN PERCENT MEDIAN PERCENT
TOTAL P HIGHER INORG N HIGHER
(mg/1) (mg/1)
0.050 45 0.320 45
~ 0.050 '" 45 0.320 45
._0.05? 44 0,330 .44
O.U54 44 0.335 44
0.055 44 0.335
_. 0.057 . 43 0.340
0.057 4} 0.340
0.057 42 O.JSO
. O.OSR 4? . 0.355
0.050 (.1 O.'.l'jS
0.051
.. 0,060
0.061
0.0h3
0.1)64
"fl.OftS
0.065
U.070
0,071
0.073
" 'b.074
0.075
0.076
0.076
0.07fi
0.078
41
40_.
40
39
39
3S
37
17
37
3ft
3ft
35
35
34
33
33
3)
33
0.355
0.360
fl.3r>0
0.380
0..3HO
0 . 3MO
0.385
0.395
0.395
0 . 315
0.410
0.410
0.410
0.410
0.410
0.420
0.440
0.440
44
.- . 43.. ...
43
42
.. . . 41
41
41
40
40
38
38
38
37
37
3ft
35
35
34
34
34
33
33
32
500-MEAN
SECCHI
(Inches)
447.000
447.600
.44fl.6.67._.._
448.667
448.667
4r>0.444_ -
450.667
451.333
451.667
452. B57
453.000
453.667
454.000
455.000
.455.000 ._
455.500
456.000
456.000
456.000
4S6.000
456.167
456.167
456.167
456.333
456.333
456.833
457.333
457.333
(Page 5)
PERCENT . MEAN CHLOR-
HIGHfR OPHYLL a
(ug/1) ~
45 12.467
45
-------
.. . TAIILE 6
MEDIAN PERCENT MEDIAN . .
TOTAL P HIGHER INORG N
iitiq/1) (mg/1)
"0.07<> 3? 0.440 """
O.Of? !•> 0.4hO
0.0*9
0.09?
0.0-J2
0.094
0.0')4
0.107
0.108
0.111
0.111
0.115
n. 1 16
_p . l ?f _
0.124
0.133
0 . 1 35
" O.I3r>
0.141
0. 1-1
0.171
0.176
0.181
O.I«S
31
31
30
30
?9
?8
?7
ft-
?5
?4
?4
?3
??
PI
21
19
0.475
0.4MO
0.4HO
0.480
0.480
0.4HO
0.4H5
0.490
0.5UO
n.soo
0.510
0.510
P.1^0
0.5)0
0.535
0.550
O.Soll
0.5/0
0.570
0.5*0
d.5«0
0.590
0.605
0.640
0.645
PERCENT 500-MEAN
HIGHER SECCHI
(Inches)
3?
32
31
29
29
28
26
2h
25
25
24
23
2?
2?
21
21
20
20
19
458.000
458.667
45H.H89
459.333
459.333
460.000
461.333
461.667
46?. 667
463.333
464.030
465.167
465.333 '
"465.333
466. 167
466.625
467.000
468.000
468.000
468.000
468.000
468.222
468.800
(Page 6)
PERCENT MEAN .CHLO(k_PERCENL ISdUNIMUH. PERCENT _ MEDIAN DIS- PERCENT ,
HIGHER OPHYLL a HIGHER DO HIGHER SOLVED P HIGHER
(ug/l)~ (mg/1) (mg/1)
32
32
31
31
30
29
29
29
28
28
27
27
26
_26_
25
25
24
23
23
23
22
22
20
20
20
20
20
19
16.475
16.600
17.167
17.600
ia.267
18.667
18.867
19.259
19.400
19.467
20.311
32
31
.31
30
30
29
29
28
28
27
27
20.517 26
21 .433 26
21.783 25
21.800
22.917
25.300
~'25."3H3"~
25.456
25.600
27.217
27.783
27.800
28.262
28.322
28.333
28.500
25
24
24
_ "?3
23
22
2?.
22
21
21
20
20
19
13.000
1.3.040._
13.200
13.220
13.300
13.400
13.400
13.600
13.600
13.600
__13.600
14.000
14.000
14.100
14.160
14.200
14.200
~14.400
14.400
14.400
14.400
14.400
14.440
14.500
|4.600
14.600
14.600
32
32.
31
31
29
29
27.
27
27
27
26
26
26
25
25
2*
24
22
22
22
22
22
21
21
15
15
0.042
0.042
0.042
0.044
0.048
0.04H
0.048
0.049
0.051
0.05.3
0.055
0.057
0.059
0.060
0.061
"0.063
0.068
0.074
0.07H
0.081
0.111
0.117
0.126
0.126
0.121
0.134
0.138
0.140
32
31
31
31
30
29
29
29
28
2H
27 53
27
26
26
25
25
24
24
23
23
22
22 "
21
21
. 20 ... ._
20 .
19
-------
TABLE 6
MEDIAN PERCENT MEDIAN
TOTAL P HIGHER INORG N
(mg/1) (mg/1)
0. HO
0.19?
.0.209
U.rMO
0.?I6
O.P11
0.?37
O.?40
0.26Q
0.?74
0, too
0.346
0..1M
0.37M
0. IMS
O.M11
0.408
0.-I7
0.476
0.4H8
14
18
14
17
17
16
14
13
12
11
11
1 1
10
10
9
g
8
8
7
7
6
O.hhO
0.660
a. 6 is
0.610
0.700
O..ZJQ
0.740
0.7HO
0. /4',
1.8IS
0 . H 1 !i
0.820
O.H40
0.8SO
U.M40
0.9PO
0.940
1.0 ?0
1 .07S
I. OHO
1.080
1.090
1.090
1.1 10
1.160
1.P80
1.310
PERCENT
HIGHER
,.
18
\l
17
16
16
IS
14
14
13
13
1?
\f
11
11
10
10
9
"
8
R
7
7
6
6
(Page 7)
SOO-MEAN . . PERCENT MEAN CHLDR- PERCENT
SECCHI HIGHER OPHYLL a. HIGHER
(Inches) (pg/1)
469.000
469.300
470.000
470. ?00
471.333
472.000
473.000
474.000
474.000
476.750
477.167
4f /. J3J
477.600
477.600
_ 477.609
477.667
479.167
479.667
480.000
480.000
480,400
481. ?SO
482.438
482,667
483.333
1«
17
17
16
'16
15 .
15 ._
14
1.J
13
' 13
11
11
11
11
10
9
8
8
8
7
7
6
2H.66?
30.167
30,800
30.878
31.180
Jl.Jbi,
33.944
3S.467
36.100
36.400
38.083
39.317
41.000
4J.9J3
44.333
44.683
48.300
4 "9.4S5"
49.467
50.567
51.367
58,550
SB. 767
61.233
69.037
,9
18
18
17
17
16
16
15
IS
14
14
13
13
12
11
11
10
10
9
9
8
8
7
7
6
t,
1 MINIMUM. PERCENT MEDIAN CIS-
DO HIGHER " " SOLVED P
(mg/1) (mq/1)
14.600
14.600
14.600
14.600
14.600
14.600
14.600
14.600
14. 700
14.700
14.700
14.700
14.700
14.740
14.740
14.760
14.800
(4.800.
14.800
14.800
14.800
14.800
14.800
14.. 800
14.800
14.1500
14.800
14.800
IS
IS
is
15
15
15
IS
: is
Jl
13
13
13
13
12
12
11
5
5
5
5
5..
5
S
-.5
5
5
5
0.140
0.141
0.1 4S
0.150
• 0.153
_. ... . 0.1S6 . ..
0.160
0.161
O.lftt
0.171
0.189
0.307
0.315
0.316
0.3PO
0.221
_ ... — 0.235
0.236
0.3SI
.. ._. . 0,382 .
0.310
0.319
0.331 ..
0.330
0 . 344
.._ . . 9,353
0.356
PERCENT
HIGHER
It
n
17
16
16
15
** ro
14
13
13
12
11
11
II
10
10
9
8
6 . .. .
7
7
.6 . .....
6
-------
TABLE 6
(Page 8)
MEDIAN
TOTAL P
0.515
i 0.600
0.620
0.919
... 0.910
0.95«
1.000
1.000 ._
,.215
1.3HO
2.000
1.660
PERCENT ...
HIGHER
5
5
4
4
._.! ..
'
? . ..
1
1
0
0
0
MEDIAN
INORG N
(mg/1)
1.310
1.415
1.410
1.430
1.535
I.57S
1.600
..960
2.150
Z.SI-i
2.640
7. 355
. PERCENT
HIGHER
5
. *
4
3 _...
3
?
?.....
I
1
0
0
0
. . 500-MEAN . ..
SECCHI
(Inches)
4H5.333
485.500
4H6.SOO
487.667
48H.444
..489.000
4H9.000
490.000
491.000
491.500
492.667
. PERCEN1
HIGHER
5
4
- ^
3
3
2
J
1
1
0
0
0
Li MEAN CHLOI
OPHYLL a
(ug/i)
fb.433
84.333
86.400
I
H/.JSO
94.467
126.100
l.ttiZfcL-
135.S25
143,5.13
198.467
248.933
381.200'
L- PERCENT
HIGHER
„
4
4
3
3
V2
2._
1
1
0
0
0
15-MINIMUH
DO
(mg/1)
14.HOO
14.HOO
14.850
14.900
14.900
14.900
14.900
14.900
14.940
14.940
.14.960
14.960
14.9HO
-PERCENT.
HIGHER
.
4
.._„_.
2
2
Z
... 2
1
1
0
" 6
MEDIAN DIS- PERCENT
SOLVED P
(ma/1)
0 . 1*0
0.383
0.416
0.482
0.635
0.6HS
0.710
0.765
0. MS
1.260
1.350
"3.580
HIGHER
5
4
4
3
3
2
1
1
0
0
ro.
o vo
-------
30
sum of the percentiles for the six parameters would be the Trophic Index
Number for the lake of interest.
An example for establishing the Trophic Index Number for Lake X is
shown below:
Value for Percentile
Parameter Lake X (From Table 6)
Total P (mg/1) 0.022 72
Dissolved P (mg/1) 0.010 73
Inorganic N (mg/1) 0.330 44
15-Minimum D.O. (mg/1) 14.8 5
500-Secchi disc (inches) 420 72
Chlorophyll a^ (yg/1) 6.5 75
Total 341 = Trophic
Index Number
From Table 4, it would be concluded that the Trophic Index Number of
Lake X (341) would place it well into the eutrophic category with a defi-
nite potential for developing nuisance bloom conditions.
It should be noted that Table 6 does not provide percentiles for every
parameter level or concentration within the range of lakes included in the
data base. This presents no problem because the data base is large enough
that selecting the percentile from the next highest or lowest listed con-
centration does not significantly influence the Trophic Index Number.
There are pristine lakes whose parameter values will be less than
the lowest shown in Table 6. In those cases, the proposed Trophic Index
would not be sensitive enough to show significant changes anyway and it
is suggested that an index number of 600 be arbitrarily assigned. This
would indicate extremely high quality, in general, but would not negate
the possibility of localized problems in some portion of the lake.
-------
31
There may also be cases where parameter values will be greater than
the maximum values listed in Table 6 for total phosphorus, dissolved phos-
phorus, inorganic nitrogen, and chlorophyll a_. If that occurs for a speci-
fic paramter, a percentile of 0 could be used. Lack of sensitivity of the
proposed Trophic Index at the lower end of the scale presents no serious
problem either since large reductions in nutrient levels would be needed
to show a marked improvement in trophic condition.
The application of Survey data to the loading concepts proposed by
Vollenweider (in press) was discussed in NES Working Paper No. 23, and
phosphorus loading data and the trophic states of 42 phosphorus-limited
Survey lakes were plotted on Vollenweider's graph of "permissible" and
"dangerous" loading rates. It was concluded that generally there was
agreement between the Vollenweider model and the Survey data.
In Figure 1, the same loading data and trophic states are plotted
on Vollenweider's graph; and the numerical Trophic Index Numbers from
Table 4 as determined by the non-weighted six-parameter percentile
method, have been added for comparison. In this case, there appears
to be agreement between the trophic ranks and the Vollenweider model,
with certain exceptions. At least some of the exceptions are believed
to be due to the fact that the existing trophic condition is the result
of previous loading rates and not necessarily the existing loading rates.
For example, the lake with the trophic rank of 357 plotted at the extreme
left and between the "permissible" and "dangerous" lines is one to which
-------
100
O»
H 10
Q
O
CO
a
o
I
Q.
CO
o
I
Q.
1.0
O.I =
• -EUTROPHIC
A-MESOTROPHIC
• -OLIGOTROPHIC
26,6 39^
OJ
ro
0.01
i
564
1*1111111
I I I i I i i i i
I i
O.I I 10 100
MEAN DEPTH (METERS) /MEAN HYDRAULIC RETENTION TIME (YEARS)
FIGURE I THE RELATIONSHIP OF TOTAL PHOSPHORUS LOADING AND LAKE MORPHOMETRY
TO TROPHIC CONDITION OF PHOSPHORUS LIMITED LAKES
1000
-------
33
the loading rate recently has been reduced; however, this lake has a
mean hydraulic retention time of eight years, and it will be some time
before the trophic condition responds to the reduced loading rate (the
model predicts an eventual mesotrophic condition).
SUMMARY AND CONCLUSIONS
A tentative Trophic State Index was developed in this report using
data collected by the National Eutrophication Survey from lakes and reser-
voirs in the northeast and north-central United States.
In general, the following can be concluded:
1. A Trophic State Index ranging from 0 to 594 and incor-
porating the parameters of total phosphorus, dissolved phos-
phorus, inorganic nitrogen, Secchi disc, minimum dissolved
oxygen and chlorophyll a_ was developed which arrayed the 209
lakes and reservoirs in a logical sequence according to their
trophic conditions.
2. Using the index cited above, lakes and reservoirs with a
Trophic Index Number of 500-594 were oligotrophic while those
with an index number of 420-499 were mesotrophic. Below an
index number of 420, the lakes became progressively more
eutrophic with the lower index numbers corresponding to a '
higher potential for developing nuisance algal conditions.
3. The Trophic Index Numbers cited in conclusions 1 and 2
are only meaningful when used in conjunction with the data
set of 209 lakes and reservoirs presented in this report.
4. Of the 44 lakes and reservoirs included in the National
Eutrophication Survey and also cited in "Problem Lakes of
the United States" (1971), 40 had a Trophic Index Number
(TIN) of less than 420 and 30 had a TIN of less than 299.
5. Lakes or reservoirs in which the trophic problem is pri-
marily aquatic macrophytes, generally do not fit the proposed
Trophic Index System; however, this is generally true of all
similar index systems.
-------
34
6. For phosphorus limited lakes, the proposed Trophic Index
Numbers corresponded well to Vollenweider's (1973) phosphorus
loading-lake morphometry-trophic state relationships which
were presented in Working Paper No. 23.
7. The proposed Trophic Index system provides a relative
method by which a previously unclassified lake could be classi-
fied after the appropriate parameters had been measured. The
Trophic Index could also be used to evaluate year to year
changes in trophic conditions of a specific lake.
8. The Trophic Index System, as presented, was developed from
lakes in northeast and north-central states. Its applicability
to lakes and reservoirs in other geographical areas is still
questionable.
-------
35
LITERATURE REVIEWED
Bartko, John J., Jon S. Strauss, and William T. Carpenter, Jr.,
1971. An evaluation of taxonomic techniques for psychiatric
data. Classif. Soc. Bull. 2(3), 1-27.
Harkins, Ralph D., 1974. An objective water quality index. Jour.
Water Poll. Contr. Fed. 46(3), pt. 1, 588-591.
Ketelle, Martha J., and Paul D. Uttormark, 1971. Problem lakes in
the United States. U.S. Environmental Protection Agency, Water
Pollution Control Research Series No. 16010 EHR 12/71.
Lueschow, Lloyd A., James M. Helm, Donald R. Winter, and Gary W.
Karl; 1970. Trophic nature of selected Wisconsin lakes. Trans.
Wise. Acad. Sci., Arts, & Ltrs, Vol. 58, 237-264.
Padron, Mario, 1969. An axiomatic basis and computational methods
for optimal clustering. Techn. Rept. #18, Dept. Indust. &
Systems Engr., U. of Florida, 171 pp.
Shannon, Earl E., and Patrick L. Brezonik, 1972. Eutrophication
analysis: a multivariate approach. Jour. San. Engr. Divn.,
Proc. Amer. Soc. Civil Engrs., Febr., 1972, 37-57.
, 1972. Relationships between lake trophic
trogen and phosphorus loading rates. Env. Sci. &
71Q-7PR
state and ni
Techn. 6(8), 719-725.
Sheldon, Andrew L., 1972. A quantitative approach to the classi-
fication of inland waters. In: Natural Environments, Studies
in Theoretical and Applied Analysis (John V. Krutilla, Ed.),
Resources for the Future, Inc. Johns Hopkins U. Press, Baltimore.
Vollenweider, R. A., (in press). Input-output models. Schweizerische
Zeitschrift fuer Hydrologie.
Winner, Robert W., 1972. An evaluation of certain indices of eu-
trophy and maturity in lakes. Hydrobiologia 40(2), 223-245.
-------
36
APPENDIX
In the following tabulation, methods and parameter combinations are:
Percentile Method-
#1 = Median total phosphorus, dissolved phosphorus, and inorganic
nitrogen; mean chlorophyll a.; 500 minus the mean Secchi disc
depth; and 15 minus the minimum dissolved oxygen.
#2 = All parameters used in #1 plus algal assay control yield.
#3 = Median total phosphorus, inorganic nitrogen, conductivity,
and total alkalinity; mean chlorophyll a_; 500 minus the
mean Secchi disc depth; and the algal assay control yield.
#4 = All parameters used in #3 except the median total alkalinity.
#5 = All parameters used in #3 except the median total alkalinity
and the algal assay control yield.
#6 = Median total phosphorus and inorganic nitrogen; mean chloro-
phyll ai 500 minus the mean Secchi disc depth; and the algal
assay control yield.
#7 = Median total phosphorus and inorganic nitrogen; mean chloro-
phyll a_; and 500 minus the mean Secchi disc depth.
Multivariate Analysis (Harkins, 1974)-
H-l = Mean total phosphorus, dissolved phosphorus, inorganic nitro-
gen, chlorophyll £, and conductivity; 500 minus the mean
Secchi disc depth; 15 minus the minimum dissolved oxygen;
and the algal assay control yield.
H-2 = Median total phosphorus, dissolved phosphorus, and inor-
ganic nitrogen; mean chlorophyll a_; 500 minus the mean
Secchi disc depth; and 15 minus the minimum dissolved oxy-
gen (note that these are the same parameters used in per-
centile method, combination #1).
-------
L« 'JVj;~»n FY LAKF 546
7 2i-J5 O HloijI'iS LAi\E 542
f 3f>3<« O 5CHSUUN LA'O'' 541
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1C 230^ AJ LI)NM L««f: 517
11 5572 ^ T^O'II LA^^ 507
1? .''•-l^ Q LA..I-- CHAKLfVUlX 503
11 't-<0-. 0"1 CA''(4\IOA|rnlA LAKE . 497
14 3MJ P*\ LONf", LAM/ 4^6
15 T-17 A^ KF'K'A LAKt'. 403
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17 tn'V ft -(AOUfTTF f'JND 4B6
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l-i 3-0^ M CA-JKT F«Ll.S w£sf«V01K 471
20 2/ml (VJ «H|Tt Ht'A'* LAr\E 464
?l ?313 M I.O.NC. |.A».F ."63
2? 5011 M KAinnuiUY Htbt^lVPIP 461
23 2f-"« M CRYSTAL LAKE 459
24 2771 M '-(flH-^IT LA^P 457
?5 500'** £ CLYOt" ^OMl) 455
26 5Tol tj LAr.F Ot^EUA 453
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-------
LA»ANK LAHE CODE L»KF NAME
^fc /
PAGE ?
INDEX NO
jo 230«
KEAG LAKE
449
J.44.
rt HOlKi'lTON LArtf
H LAKE CAHLOS
LA*E.
3.1 ?7H
M
.OC«>N'i"'>«0£.
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•=3 330h
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KELLV FALLS POND.
CHAIITAUOUA LAKE
_t!'-'1t IN'-'TON LAKE
IS •'UNO
403
__29L-
393
.391
_l«Lfl_
3«7
35
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3V~
VV-
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35*
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U
3?
37
53
V/
93
V9
-------
L»' MILL POND
S<* ?7rf4 £ nn^LINC. LAKE
fiC 3h33 £ SVtATOilA LAKH
fl S1^1^ " ££ OSAUOMEE LAKE
1? 27M p MlNNF^aSKA LAKE
63 ?t-t***f;, SANFOl'U LAKE
(,14 <=,^hf, £ ttOUNO LAKE
*S 3>.0? f£ KLACK L<**F
<.ft ?7-»3 £ TsMOI LAKK
M gi,i.-J*rg MANISTEF LAKE
._ h« ?7|S A^ CAsS LAKF
(."> ?717 ^. Ocll I LAKE
70 ?7*5 f LE MIH"F I11EU
71 ->A40 g: L')^ ST .JElilS
If ?7i.H (£ LA-^K Of THE WOOUS
7.1. 3f>'JS £ OTTEM LAKE
71» 3S13 ^ 00"l>YF.A" LAKE
7, ?7A, *0F0-.STLAKF
76 ?7-M Jj ME'dlMlN LAKE
77 SS7>. 0 KILL')* "ESErtVOH
7X ?7C1 £ LAKF HFwlO.II
7O ?M1 ^ HL^CfvOurN LAKE
p*0 4^0^^* & SL .iT^^^V T LI *•" BFSFNVOIrt
PI ?^°.- ^ u!f'»F. MAWtlOETTE LAKK
«? ?<..^^ £ •MITE LAKE
„ 0,0, t HA.^LAKE
3R5
3rt3
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373
372
37P
371
370
3f,£
M?
365
3M ..
358
357"
3?5
3,3
3b2
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347
345
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34?
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334
332
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-------
L»i(K..
CODE CAKE NAME
PAGE *
INDEX NO
«S 3*M g
H? 2n71
01 5305
a? 0--1?
°i SSSi
OS 2*00
97 ?7-iO
100 SS73
101 SSSO
10? 5^76
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100 SSsJ
100 3MQ
110 2*07
111 55»-2
11? 2717
, AU.E,,^Y -«EB,o,R
PELICAN LAKt
Wits* WESFWVUIM
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OLENN LA^K
SH^LTON LAKE
t AN1-" \1 1 S^OT A
ptlCMOALE ^ONO
CLF.,'.-«4T^« LAKE
NEST LaKf
SEHASTirOOK LAKF
LOW 1. AKE
KA^Ol-ASSET LAKE
'^LAC^>JOOF LAKE
UNI UN LAKK
rtVNsiANriuK UESEWVOIR
riOI.LDXAY' XE^EHVOIH
KAvLEtfHLK LAKf
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l_A",r coh
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171
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-------
LMPS RANKER BY INDEX NOS.
LAKE CODE IAK.E NAME
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INOFX NO
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