United States
          Environmental Protection
          Agency
Office of Water
Nonpoint Source Control Branch
Washington, DC 20460
EPA 440/5-89-003
1989
oEPA   Report to Congress:
          Water Quality of the Nation's Lakes
                                                  Printed on Recycled Paper

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         Report to Congress:

Water Quality of the Nation's Lakes
           Nonpoint Source Control Branch
        Office of Water Regulations and Standards
               Office of Water
         U.S. Environmental Protection Agency
                  1989
                   BBfiaES—.
60604-3590

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AT

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                           Contents
Foreword  	



Executive Summary



Problem Definition
1



3



5
Pollution Control and Lake Restoration  	15
                                iii

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                                      Foreword
   ection 314 of the Clean Water Act, as amended by
the Water Quality Act of 1987, requires the States to
submit to the Environmental Protection Agency, as
part of their 305(b) biennial reports, information on
the water quality of their lakes, including:

   (a) an identification and classification accord-
      ing to eutrophic condition of all publicly-
      owned lakes in such State;
   (b) a description of procedures, processes,
      and methods (including land use require-
      ments), to control sources of pollution to
      such lakes;
   (c) a description of methods and procedures,
      in conjunction  with appropriate  Federal
      agencies, to  restore the quality of such
      lakes;
   (d) a description of methods and procedures
     to mitigate the  harmful effects of  high
     acidity, including innovative methods  of
      neutralizing and restoring buffering capa-
     cities of lakes and methods of removing
     from lakes toxic metals and othertoxic sub-
     stances mobilized by high acidity;
  (e)  a  list  and description of those publicly-
     owned  lakes in such state for which uses
     are known to be impaired, including those
     lakes which are  known  not to  meet ap-
      plicable water quality standards or which
      require  implementation  of control  pro-
      grams to  maintain  compliance with  ap-
      plicable standards and those lakes in which
      water quality has deteriorated as a result of
      high acidity that may reasonably be due to
      acid deposition; and
   (f) an assessment of the status and trends of
      water quality in lakes in such State,  includ-
      ing but not limited to, the nature and extent
      of pollution loading from point and non-
      point sources and the extent to which the
      use of the lake is  impaired as a result of
      such pollution, particularly with respect to
      toxic pollution.
   The Act,  as amended,  further requires the Ad-
ministrator of the Environmental Protection Agency
to transmit to the Senate Committee on Environment
and  Public Works and House Committee  on Public
Works and Transportation  a report on the status of
water quality in our Nation's lakes.
   The following report summarizes the information
submitted by the States  in response to the April 1,
1988 legislative  requirements described;   where
necessary, information developed by EPA supple-
ments the State-reported data. This Report to Con-
gress, therefore, represents the Agency's  summary
of the water quality of lakes throughout this Nation as
currently perceived and documented by the States in
response to Section 314.

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                           Executive Summary
 Status

 The status of water quality in our Nation's lakes has
 been  assessed  according  to  use  impairment,
 threatened uses, and trophic condition (a measure
 that determines the "aging process" of a lake). Of
 12,413,837 lake acres assessed by 34 States, 25 per-
 cent were found to be impaired or partially impaired,
 and 20 percent threatened by pollution. "Threatened"
 waters refers to those lakes that fully support their
 designated uses but that may not fully support uses in
 the future because of anticipated sources or adverse
 trends of pollution.  Approximately 50 percent of
 22,000 lakes classified by trophic status were either
 eutrophic or hypereutrophic (nutrient-rich or "old").
   From  a  national  perspective,  a  statistically-
 designed sampling framework was not used to es-
 timate the water quality of lakes across the country.
 Therefore, this report cannot state actual status and
 trends or classify the trophic condition of the Nation's
 lakes with statistical  confidence.  The  numbers
 reported  in the 1988 assessments are in many cases
 incomplete.


 Causes of Impairment and
 Sources of Pollution
 States identified  12 specific causes of use impairment
 in lakes, with nutrients and siltation/turbidity the most
significant pollutants.  Nutrients are elements, primari-
ly phosphorus and nitrogen, that promote plant and
 algae growth. Excessive nutrients may increase the
 productivity of  the  lake to the point where algal
 blooms and aquatic vegetation impede recreational
 activity and diminish the lake's aesthetic value. At the
 end of their growing season the algae and aquatic
 vegetation die,  and  their decomposition consumes
 dissolved oxygen. Such oxygen depletion results in
 conditions unsuitable for fish; severe depletion  may
 cause fish kills.
   Siltation is the process by which soil or rock is car-
 ried by water to a lake and deposited as sediment. As
 the silt settles, the lake becomes more shallow, often
 producing  conditions that stimulate macrophyte
 (aquatic plant)  growth.  Dense vegetation,  shallow-
 ness, and changes  in lake bed/sediment composi-
 tion adversely affect  recreation and fish habitats. The
 habitat  suitable for  coolwater sport fisheries may
 decline or even disappear.
   Turbidity is an indirect measure of the transparen-
 cy (light penetration) of the lake. High turbidity result-
 ing from matter suspended  in the water  reduces
 transparency, producing what is often perceived  as a
 "cloudy" condition. High turbidity also inhibits algal
 productivity and may affect feed ing habits of fish  and
 food chain organisms.
   States classified the sources of pollution causing
 use impairment as  either  point source, nonpoint
 source,  or natural. According to the States, 76 per-
 cent of the pollution  affecting lakes originates from
 nonpoint sources, 11 percent from point sources,
and 12  percent from natural sources. Agricultural

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nonpoint source runoff  was the most frequently
reported source; however, urban runoff and resource
extraction (mining) are major sources in specific
areas.

Pollution Control and Lake
Restoration
The sources of pollution to a lake, be they point or
nonpoint, will determine the approach used to control
pollution.  Point  sources  are  usually  controlled
through wastewater treatment and permit programs.
Nonpoint sources, because they are  diffuse by na-
ture, are best controlled by watershed management.
   Once the sources of pollution have been success-
fully addressed, in-lake restoration may begin. The
specific causes of  use impairment in the  lake will
determine the restoration techniques to be used. For
example,  nutrient  inactivation   may  reduce  or
eliminate algal blooms, while dredging will deepen a
shallow lake, and  harvesting can remove rooted
vegetation. In this report, lake restoration techniques
are organized and explained by six basic objectives:
(1) control of algae; (2) deepening; (3) removal of
rooted vegetation; (4)  improvement of fisheries; (5)
acid mitigation; and (6) toxic removal.

Trends
Information that can be used to define water quality
trends in lakes is extremely limited. Many lakes have
been sampled only once or twice during the past 15
years and the range of seasonal and annual fluctua-
tions in key parameters is not well documented. To ac-
curately reflect trends in lake water quality, data must
be collected consistently over several years. Of the 38
States  reporting the water quality of their lakes  in
1988, most did not have the baseline data necessary
for trend analysis.
   In comparison with the 1986 305(b) report, how-
ever, the number of lakes considered eutrophic in-
creased more than 10 percent, while the number of
mesotrophic and oligotrophic lakes decreased 8 and
7 percent, respectively. This finding is based on more
extensive data, with 63 percent more lake acres as-
sessed in the 1988 Lake Water Quality Assessment
than by the 1986305(b) report.
  The baseline data therefore are building, and will
be further augmented in future 305(b) reports by ac-
tivities authorized by the Water Quality Act of 1987.
Grants made under Section 314 as well as the con-
tinuing emphasis on lake water quality assessment
will strengthen both the quantity and quality of data
on the water quality of this Nation's lakes.
   Lakes are being considered as ecological units
subject to many factors, and monitored fora number
of significant parameters  in addition to traditional
trophic state parameters. As technical and scientific
knowledge of lake systems continues to grow, along
with our database of lake water quality information,
understanding the changes that are occurring in lake
water quality also increases.

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                             Problem  Definition
 Introduction

 In the 1988 Lake Water Quality Assessments, most
 States identified a lake as "impaired" or "threatened" in
 terms of designated uses being met, a relatively new
 concept now generally accepted as the most realistic
 appraisal process for lake waters. Lake acres that
 were reported "not meeting" or only "partially meet-
 ing" designated uses were considered impaired, al-
 though the criteria used to determine impairment vary
 from State to State according to differing regional ex-
 pectations of lake water quality.
   States also identified their lakes  according to
 trophic  condition.  Traditionally,  the  trophic  state
 designation has been used to classify a lake accord-
 ing to its nutrient status. Eutrophication, a general
 measure of nutrient status, can be viewed  as an in-
 dication of the lake's natural aging process, the chan-
 ges  that  normally occur  over  hundreds  even
thousands of years, evolving the lake into a wetland,
and finally, dry land (Fig. 1). Although a natural evolu-
tion, the eutrophication process can be accelerated
by human activities. "Cultural eutrophication" is the
term applied to the effects of human activities on
water quality (e.g., careless use of detergents, fer-
tilizers, and pesticides, unwise waste disposal, poor
mining and construction practices) and result in per-
turbations that can usually be reversed.
  The eutrophication progression can be described
by a series of trophic states:
  • Oligotrophic - clear waters with little
     organic matter or sediment, and minimum
     biological activity;

  • Mesotrophic - waters containing more
     nutrients and therefore exhibiting more
     biological productivity;
  • Eutrophic — waters extremely rich in
     nutrients, with high biological productivity;
  • Hypereutrophic - murky, highly productive
     waters, closest to the wetland status.
General Characteristics of Traditional Lake
CHARACTERISTICS OLIGOTROPHIC
Nutrient Level Low
Organic Matter Content Low
Biological Productivity Low
Lake Age Young
Water Transparency High
Oxygen Depletion Hypolimnion No
Average Depth Oeep
Trophic Status Classifications
MESOTROPHIC
Medium
Medium
Medium
Medium
Medium
Yes
Moderate

EUTROPHIC
High
High
High
Old
Low
Yes
Shallow

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NATURAL
         OLIGOTROPHY
                                           MESOTROPHY
                                                                    EUTROPHY
                                                                                  HYPEREUTROPHY
TIME

MAN INDUCED
1000'S OF YEARS
                            100'S OF YEARS
                                                           YEARS
                                               EUTROPHY/HYPEREUTROPHY
                               10'S OF YEARS
                                                                                               E/H
Figure 1.—Above: The progression of natural lake aging or eutrophication through nutrient-poor (oligotrophy) to nutrient-rich
(eutrophy) states. Hypereutrophy represents extreme productivity characterized by algal blooms or dense macrophyte popula-
tions (or both) plus a high level of sedimentation. The diagram depicts the natural process of gradual nutrient enrichment and
basin filling over along period of time (e.g., thousands of years).
Below: Man-inducted or cultural eutrophication in which lake aging is greatly accelerated (e.g., tens of years) by increased in-
puts of nutrients and sediments to a lake, as a result of watershed disturbance by man.
   Dystrophic is also a lake classification but not
necessarily a part of the eutrophication progression.
Dystrophic systems  are  often low in nutrients yet
highly colored with dissolved humic organic matter
(sphagnum bog).
   The trophic state of a lake is most commonly
determined by using Carlson's Trophic State Index
(TSI). This index  was developed from  the inter-
relationships  of summer transparency (clarity of the
water as measured by the Secchi disk), epilimnetic
concentrations of chlorophyll a, and total  phos-
phorus. The TSI values range between 0 and 100 with
increasing values indicating more eutrophic condi-
tions.
   When considering the results of the TSI calcula-
tions, one should keep in mind the assumptions on
which the Carlson formulae are based: (1)  Secchi
transparency  is  a  function  of  phytoplankton
biomass; (2) phosphorus is  a factor limiting algal
growth; (3) total phosphorus concentration is direct-
ly correlated with algal biomass. Therefore, Carlson's
                           TSI may not be applicable to lakes where suspended
                           solids are a major source of turbidity, when nitrogen
                           is the factor limiting algal growth (as is the case in
                           Delaware and many southern U.S. lakes), or when
                           total phosphorus  does not  correlate with algal
                           biomass.
                             To compensate for these  inadequacies, several
                           States have developed other ways to determine the
                           trophic  status of  lakes.  For  example,  Indiana
                           measures seven parameters in addition to the three
                           used for Carlson's TSI: dissolved phosphorus, or-
                           ganic nitrogen, nitrate, ammonia, dissolved oxygen,
                           plankton, and light transparency.
                           Trophic State and Lake Uses

                           Although changes in lake water quality may be track-
                           ed by monitoring for trophic state, experience has
                           shown that the trophic state of a lake does not always
                           define its  use. Some States believe that advanced
                           eutrophication does not necessarily eliminate a lake's

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 designated recreational uses,  nor is an oligotrophic
 lake  always best for recreational activities. These
 States have recognized this apparent disparity be-
 tween positive recreational uses and the negative
 connotations associated with  eutrophic conditions,
 adjusting the ways they determine trophic status to
 reflect desired use (such as warmwater fishing) and
 public perceptions in addition to measurable physi-
 cal, chemical, and biological parameters.
   A eutrophic condition, therefore, is not necessarily
 "bad" in terms of using the lake, nor are eutrophic or
 mesotrophic conditions necessarily  abnormal  or
 outside of ecological expectation based on lake and
 watershed characteristics.  For example, most lakes
 assessed in Iowa and Nebraska either  fully or partial-
 ly support designated uses, even though all 114 Iowa
 lakes are classified  as  eutrophic, and 22 of 23
 Nebraska lakes evaluated are either eutrophic or hy-
 pereutrophic. However, as the aging process ac-
 celerates  (usually  because  of   cultural  eutro-
 phication), the lake and its watershed require greater
 management to maintain the lake's designated uses.
   Table 1 summarizes the trophic status of lakes as
 reported  by the States. The total  number of lakes
 listed is the number assessed, not the total number of
 lakes in the State. The assessments were done by in-
 lake  monitoring and evaluation (based on profes-
 sional judgement,  lake   uses,  known  pollution
 sources,  and other  subjective information).  One
 problem with accumulating and interpreting the data
 presented from the States  is that the data are col-
 lected in a variety of ways: most states have not per-
 formed a complete census on their lakes and there is
 no indication as to why the lakes they assessed were
 selected. If the lakes were assessed in  response to a
 problem or public complaint, or based on easy ac-
 cessibility, rather than on random selection, there is
 probable bias in the reported information. It is likely
 that the more remote and/or pristine lakes are under-
 represented in some State assessments.
   Given the limitation on the data compilation, the
 States reported that 50 percent of all lakes assessed
 for trophic status  were  either eutrophic  or hyper-
 eutrophic (Fig. 2);  24 percent,  mesotrophic; 11  per-
 cent,   oligotrophic;  and   less than   1   percent,
 dystrophic. Trophic status for the remaining 15 per-
 cent assessed was unknown.
   Of  the total acres assessed  in 34 States, 25  per-
 cent were reported as impaired and 20  percent were
 considered threatened (Table 2). The States used dif-
ferent criteria in  developing the categories of  "im-
 paired"  and  "threatened";   therefore, the  results
should not be compared among States. Of the States
that reported, New Jersey did not indicate impair-
          Unknown
                                   Hypereutrophic
                                   excessive nutrients)
                                        and
                                     Eutrophic
                                     (nutrient rich)
 Oligotrophic
(minimal nutrients
    Mesotrophic
    (some nutrients)
  * assessed for something other than trophic state

 Figure 2.—Lakes in each trophic status classification as
 reported by States for all U.S. lakes assessed (%).
 ment (because of insufficient monitoring data), but
 did list its total 51,000 lake acreage as "threatened."
    States are  becoming increasingly  aware that
 eutrophic condition is to be considered in the context
 of lake and watershed history, characteristics, and
 uses; not negatively, but comprehensively to show
 the overall  condition  of the  lake.  Determining
 whether a lake is supporting  designated uses helps
 the lake manager or concerned individual assess the
 lake's "health." That assessment also may point to
 potential problems that can be averted to protect the
 future health of the lake.
 Causes of Use Impairment

 States identified  12  specific causes of pollution in
 lakes with impaired uses (Table 3). Nutrients and silta-
 tion/turbidity were two significant pollutant groups.
 These factors play principal roles in determining a
 lake's trophic state. For example, Minnesota reported
 that 75 percent of its citizen complaints concerned
 eutrophication, usually identified as algal blooms and
 directly related to excessive nutrients. Algal blooms
 were also reported as a problem in North Carolina. Sil-
 tation is a concern in South Dakota, where several
 lake restoration projects  have been designed to
 remove sediment.
   Nutrients are elements, primarily phosphorus and
 nitrogen, that promote  growth,  especially that of
 plants and algae. Excess nutrients may increase the
 productivity of the  lake to the point where algal
 blooms and aquatic vegetation impede recreational
 activity and diminish the aesthetic value of the lake.
   Siltation is the process by which particles of soil or
 rock are carried by water to a lake and deposited as
 sediment. Turbidity is an  indirect measure  of the
transparency (light  penetration)  in  the  lake; high
turbidity results from matter suspended in the water

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                                    Table 1. - Trophic status report.
STATE
AL
AR
CT
DE
DC
FL
ID
IL
IN
IA
KS
KY
MD
MA
Ml
MN
MS
NB
NV
NH
NY
NC
ND
OK
OR
PA
PR
Rl
SC
TN
UT
VT
VA
WA
Wl
TOTALS
LAKES ASSESSED
35
71
160
31
3
91
554
412
404
114
193
92
59
478
682
12,034
127
23
9
415
3,340
144
216
74
204
37
18
54
41
119
127
-
248
140
2,153
22,902
OLIGO-
4
0
34
0
0
57
0
2
75
0
0
14
2
133
98
1,203
0
0
1
161
85
11
0
5
46
1
0
4
0
21
33
19
20
58
605
2,692
MESO-
16
59
78
0
1
19
55
25
144
0
68
27
13
289
367
3,009
0
1
4
172
132
21
0
49
78
29
3
41
0
33
44
72
49
24
746
5,668
EU-
11
4
17
31
0
13
499
239
67
114
125
51
44
56
217
7,822
33
12
4
82
84
25
216
8
69
7
14
9
40
55
50
28
120
45
802
11,013
HYPER-
0
0
0
0
0
0
0
146
0
0
0
0
0
0
0
0
0
10
0
0
0
9
0
12
11
0
0
0
1
10
0
0
0
0
0
199
DYS-
0
0
0
0
0
0
0
0
118
0
0
0
0
0
0
0
0
0
0
0
0
8
0
0
0
0
0
0
0
0
0
11
1
0
0
138
UNK*-
4
8
31
0
2
2
0
0
0
0
38
0
0
2,381
0
0
94
0
0
0
3,039
70
0
0
0
0
1
0
0
0
0
589
58
13
0
6,330
"Unknown means these lakes were either not assessed or not assessed for trophic status.
states not listed in the table either did not report the information or reported in a way that was inconsistent with the format of
the table.

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          Table 2. — Impaired and threatened lakes.
                          ACRES
STATE
AL
CT
DC
FL
GA
IL
IN
IA
KS
KY
LA
ME
MD
Ml
MN
MS
MO
NE
NC
NH
NY
ND
OH
PR
Rl
SC
SD
TN
VT
VA
WA
WV
Wl
WY
REPORTED
504,336
82,900
377
2,085,120
417,730
305,847
104,540
81,400
175,189
228,385
713,719
994,560
32,583
840,960
3,411,200
500,000
288,012
145,300
305,367
151,000
750,000
625,503
117,323
11,146
16,520
963,000
1,598,285
538,657
229,146
161,562
613,582
23,460
971,000
411,244
ASSESSED
491,566
37,562
136
947,200
417,730
183,572
104,540
80,249
173,911
214,483
517,476
994,560
17,448
424,021
1,435,554
500,000
288,012
85,518
305,367
149,854
750,000
619,333
90,771
11,146
16,089
410,407
662,532
538,657
227,121
161,089
156,518
19,171
971,000
411,244
IMPAIRED
86,080
12,389
136
637,440
5,373
160,641
179
53,448
57,256
35,148
141,141
38,211
2,610
119,836
236,845
18,260
2,311 j
3,214
11,897
19,146
295,332
48,125
59,835
7,345
1,401
1,165
94,720
86,648
49,206
13,737
33,684
19,171
722,000
23,239
THREATENED
-
8,176
0
-
140
22,455
104,361
18,902
116,655
152,544
87,034
-
4,606
161,894
-
-
-
-
50,330
4,603
29,942
570,170
25,733
1,745
11,425
-
548,000
75,828
153,319
-
116,210
0
179,300
146,491
TOTALS    18,398,953    12,413,837
3,095,438
2,485,502
- State did not report this data.
Percent impaired = 25 percent; Percent threatened = 20 percent.
states not listed in the table either did not report the information or reported in a
way that was inconsistent with the format of the table.
 that creates what may be perceived as a
 "cloudy" condition. As the material set-
 tles, the  lake  becomes more shallow,
 often  producing  conditions  that en-
 courage  macrophyte  growth.  If  this
 vegetation becomes too dense, it may af-
 fect both recreation and fish habitats. A
 lake that becomes too shallow may im-
 pede recreational activities such as swim-
 ming, boating, and fishing.
   Metals and inorganics also were iden-
 tified as significant causes of use impair-
 ment in lakes. Metals include cadmium,
 lead, zinc, copper, silver, iron,  and  man-
 ganese.  The largest cause  of impaired
 lake use in North Carolina has been dis-
 charges  from coal-fired power plants to
 two lakes (Belews and Hyco), producing
 excessive selenium levels in  these lakes.
 This selenium contamination has caused
 a drastic decline in fish population and
 reproduction in both lakes.  Metals (iron
 and manganese), generated  by active
 and abandoned  coal  mining, are  sig-
 nificant factors affecting lake use in West
 Virginia.
   Mercury  is  the principal  inorganic
 responsible for impairment in lakes. Mer-
 cury contamination has been a problem
 in northeastern Minnesota lakes, where a
 study is  being conducted to determine
 the source of the mercury. Most fish can
 be consumed from 92 percent of the large
 lakes (greater than 5,000 acres) sampled,
 but fish cannot be eaten from 1 percent.
 Of the small lakes (less than 5,000 acres)
 sampled,  some  fish can be consumed
 from 80 percent.
   Organic enrichment and low dissolved
 oxygen (DO) also account for some of the
 use impairment  in lakes. The  biological
 decomposition of organic matter - from
 agricultural runoff, algae, aquatic vegeta-
 tion,  and/or  municipal/industrial   dis-
 charge  -  consumes  oxygen. If the
 oxygen is consumed more rapidly than it
 can be replaced, the oxygen supply may
 be  depleted to the extent that fish are
 stressed  or unable to survive. Of the fish
 kills reported in Nebraska and Minnesota,
 71 percent and 69 percent, respectively,
 resulted from such conditions.
  The presence  of pathogen  indicator
organisms may also restrict the use of

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                Table 3. - Major causes of pollution in lakes with impaired uses (% acres).4
STATE
CT
FL
IL
IN
KS
KY
LA*
MD
MN
MS*
MO
NH
NM
NY
NC
OH
OK
PR
Rl
SC
SD
VA*
VT
WA
WV
AVERAGE
NUTRIENTS
36
7
15
32
<1
19
33
99
62
34

24
31
36
11
21
23
30
19


45
20
69
12
27
a

1

8






1
76

6



3



10
<1

29
5
SILTATION/BURBIDITY
15
15
48

<1
13
6
1

33


16

4
23
38
20
5

80
10
8

20
15
ORGANIC ENTIRCHMENT/DO
4
15
19
22

•
11





53
<1
10

5
19

5

29
5


8
THERMAL MODIFICATION




















<1
2


11
1
FLOW ALTERATION




<1





75


12
<1







13
6

4
OTHER HABITAT MODIFICATION












<1




6

74





3
PATHOGENS
6
<1
1
12


27






1

2
<1
7
76

14
<1
5
6

6
AQUATIC PLANTS & ALGAE
22
8
9











22
29






49
1

6
PESTICIDES


4
3


<1


31
24


9

2
9




<1



3
PRIORITY ORGANICS


1
7




2




36


4






6

2
METALS/INORGANICS
1
27
2
4
100
67
13

36
2



<1
53
14
12
8


4
4

6
28
15
OTHER*
16
27
1
12

1
9






<1

9
10
6

21
2


6

5
** These numbers represent the relative impact of each pollutant on the use impairment in lakes.
#This category includes primarily unknown toxicity, non-priority organics, and taste/odor problems associated with water supplies.
•Identified no major causes; however, these moderate/minor impacts cause the use impairment in lakes.
states not listed in the table either did not report the information or reported in a way that was inconsistent with the format of the table.
                                                        10

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 lakes. Tests for fecal coliform bacteria are commonly
 used as an indicator of human or animal wastes con-
 taminating water bodies. Such contamination often
 may result from runoff from animal feed-lots, rural or
 urban areas heavily populated with domestic and/or
 wild animals,  or improperly treated municipal was-
 tewater, including combined  sewer overflows. The
 feces from  warm-blooded animals contains many
 pathogens,  some causing disease in humans. There-
 fore, the presence of fecal indicator organisms in a
 lake may lead to restrictions being placed by public
 health  officials  on  contact recreation  (e.g., swim-
 ming)  and  fish consumption.  The  feces  from
 warmblooded animals may also contain pathogens
 that cause  disease and perhaps fish kills.  For  ex-
 ample, in Kansas most of the reported fish kills can be
 traced  to  pathogens  from  animal feedlots  and
 agricultural  runoff.
   Impairments  caused by  thermal modification
 usually result from warmwater discharges (primarily
 from some type of cooling process) into a lake or its
 tributaries. This temperature  increase adversely af-
 fects the sport fishery that prefers cool water. Reser-
 voir releases or withdrawal of cool bottom water may
 also  limit  or destroy  the habitat  for coolwater
 fisheries. Flow alteration can impair lakes in  various
 ways. Most  typical is  either decreasing  inflow or in-
 creasing outflow, both of which lower the water level.
 This may limit fish habitat and recreational activities.
   Acidic conditions can also adversely affect the fish
 population of a lake. pH is a measure of the hydrogen
 ion concentration in the water and is used to indicate
 acidity or alkalinity. A pH of 7.0 is considered neutral,
 pH less than 7.0  is technically acidic, and pH greater
 than 7.0 is alkaline.  According to the National Acid
 Precipitation Assessment Program (NAPAP), most
 fish populations  tolerate pH levels between 6.0 and
 9.0 without apparent difficulty; significant impact on
 some species  begins at pH = 5.5; serious damage
 for almost all species occurs below 5.0; and relatively
 few species  can sustain populations in waters below
 pH = 4.5. The pH at which a State considers a lake
 impaired may vary  depending on various charac-
teristics of the lake  and fish species present. The
lake's ability to offset  changes in pH  (buffering
capacity) must also be considered since small chan-
ges in pH can harm aquatic life.
   Although only a few States have assessed the ex-
tent of  adverse  impacts resulting  from  excessive
acidity, it appears that relatively few lakes have low
pH values. For example, only 9 lakes with pH values
less than 4.5 were reported in  Massachusetts and 4
lakes  in New Hampshire.  New  Hampshire also
reported 27 lakes with pH between 4.5 and 5.0. Of the
 1,000 lakes sampled in Maine, the State reported 50
 with a pH less than 5.0, and Wisconsin estimated be-
 tween 100 and 200 lakes are acidic. However, States
 indicated that many more lakes are considered sen-
 sitive to acidic inputs because of their low buffering
 capacity. Acidic  inputs to a lake may result from
 precipitation, mine drainage, or naturally decompos-
 ing humic material.
    Toxic is defined by EPA as any pollutant or com-
 bination of pollutants that harms aquatic or terrestrial
 life or adversely affects human health. Although low
 dissolved oxygen, pathogens, and acidity may have
 toxic effects on aquatic life, most States reported
 their toxic  problems in terms  of  more priority
 toxicants such as pesticides, organics, metals, and
 inorganics. Most  of these toxicants can accumulate
 in the food chain and thereby pose a public health
 problem if contaminated fish are consumed. These
 toxicants are considered "priority" in that they are
 listed as such by the Environmental Protection Agen-
 cy pursuant to Section 307(a) of the Clean Water Act.
   Twenty-one  States reported the detection of
 priority  toxicants,  most  often  PCBs,  pesticides
 (chlordane, atrazine, alachlor), metals, and mercury.
 These pollutants were found in lake water,  sediment,
 and fish tissue. Priority pollutants usually are  not
 found statewide,  but in specific local areas, where
 they result from  extensive urban  or agricultural
 runoff, mining  activities,  or  industrial point source
 discharges.
   In many instances, levels of priority pollutants war-
 rant fishing bans or consumption advisories such as
 have been in place for sport fish consumption in Il-
 linois d uring the past few years. New York also has is-
 sued consumption advisories for almost 40 water
 bodies and banned fishing in the Upper Hudson be-
 cause of high levels of PCBs in fish. To control fish
 consumption, fishing at Syracuse's Onondaga Lake
 was once banned. Even though it is now allowed as
 recreation, people are warned not to eat their catch.
   Pesticides are  chemical  compounds   used  to
 destroy pests in both agricultural and urban areas.
 They include chemicals such as chlordane, atrazine,
 alachlor,  dieldrin,  DDT, and  toxaphene. In Kansas
 lakes, detectable concentrations of agricultural pes-
 ticides (e.g., atrazine and alachlor) were found in 34
 percent of the 128 lakes sampled for pesticides. As-
 sessment of fish tissue, a more sensitive indicator
 than lake water of some toxicants, demonstrates a
 more widespread  effect. Fifty-seven percent of the
 lake acres assessed in Kansas exceeded the Nation-
 al Academy of Science guidelines for protection of
 predators, with chlordane,  PCBs, dieldrin,  and hep-
tachlorthe principal causes.
                                                11

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  Urban activities have also affected
Kansas lakes, with two 1986 intensive
lake surveys finding elevated levels of
chlordane residue in the edible portion
of fish. A correlation was established
between high chlordane  levels and
urban areas.
  Priority  organics   include  such
chemicals  as  PCBs,  phenols, and
dioxin. PCBs are most often reported
as  a  problem in lakes. PCBs are a
group of toxic,  persistent  chemicals
used  to  insulate transformers and
capacitators  and to  lubricate gas
pipeline systems. Of the lake acres
monitored for toxicants in  New York,
approximately  20 percent were  af-
fected to some degree by PCBs or
pesticides, with fish consumption ad-
visories in effect for several lakes be-
cause  of  PCB-contaminated sedi-
ments.  Ground-based sources such
as landfills appear to be the source of
these pollutants.

Sources of Pollution
States classified the sources of pollu-
tion causing use impairment as either
point  source,  nonpoint  source,  or
natural.  Table  4  summarizes these
sources by  State, with 76  percent
originating from nonpoint sources, 14
percent from point  sources,  and 10
percent from natural sources.
    Point sources are defined as dis-
crete  conveyance discharges (e.g.,
through a pipe) and include municipal
and industrial  discharges and com-
bined sewer overflow. Most nonpoint
source pollutants are transported by
surface runoff,  groundwater,  and at-
 mospheric deposition. These  pol-
lutants originate from streets, lawns,
 construction sites, forests, mines, and
 agricultural lands. Point sources  are
 usually chronic and site-specific in im-
 pact,  whereas nonpoint sources  are
 episodic and/or diffuse.
    An objective definition  of "natural"
 sources  of  pollution has not been
 developed; therefore this report relies
 on the States  categorization and is
 somewhat variable. For example, one
Table 4. - Major known sources of pollution in lakes with
impaired uses (%).
STATE
CT
FL
IL
IN
KS
KY
LA
ME
MD
MN
MS
MO
NH
NM
NY
NC
ND
OH
OK
PR
Rl
SD
VA
WA
WV
POINT
SOURCE
49
12
4
58
0
8
12
2
3
27
0
0
0
0
6
35
0
17
0
1
0
2
1
2
46
NONPOINT
SOURCE
20
88
96
42
2
26
87
98
97
73
100
100
70
100
94
63
100
83
100
55
100
96
63
98
54
NATURAL
31
0
0
0
98*
66
1
0
0
0
0
0
30
0
0
2
0
0
0
44
0
2
36
0
0
PREDOMINANT
CATEGORY
Municipal
Agriculture
Agriculture
Municipal
Mineral-Intrusion
Lake Sediments
Agric./Urban Runoff
-
Agriculture
-
Agriculture
Flow Modification
Acid Precipitation
Agric./Recreation
-
In-place contaminants
Agriculture
Agriculture
Agriculture
Urban Runoff
-
Agriculture
Agric./Urban Runoff
Agriculture
Resource Extraction/
Industrial
 AVERAGE  11
76
                                   12
 * Use impairment in Kansas is identified by the violation of water quality criteria. The
 criteria established in the state of Kansas do not adequately reflect the agricultural
 NPS impacts on the lakes. Additional information shows well over 50 percent of the
 total lake impacts result from agricultural NPS pollution.
 states not listed in the table either did not report the information or reported in a way
 that was inconsistent with the format of the table.
                                                  12

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 State considered in-place contaminated  lake sedi-
 ments as a nonpoint source whereas another State
 considered  contaminated  sediments  a  natural
 source of pollution. Generally, mineral intrusion and
 salinity are considered natural sources of pollution
 and reflect the geology of the area, except in heavily
 irrigated sites.
   Figure 3 shows  how nonpoint sources such as
 precipitation, surface runoff, and groundwater, plus
 the natural geology and topography of the land can
 influence the water quality of lakes. This hydrologic
 cycle illustrated the balance between water inputs
 and outputs that influences lake water quality. Inputs
 include direct precipitation, groundwater, and sur-
 face runoff; whereas outputs are surface  discharge
 (outflow), evaporation, losses to groundwater, and
 water withdrawn for domestic, agricultural, and in-
 dustrial purposes.
   Most States find  nonpoint sources of pollution
 responsible for most of the use impairment in lakes,
 several attributing 100 percent of the impairment to
 nonpoint sources.  Agricultural  nonpoint  source
 runoff  was the  most frequently reported source.
 Nebraska observed that "even where domestic point
 sources are indicated as being partially responsible
 for this problem, it is suspected that the effect of non-
 point sources would still preclude support of the use
 if  the  point sources  were  eliminated." Vermont
reported   nonpoint   sources  "now  the  most
widespread remaining water pollution problem af-
fecting the quality of the State's water."
   One notable exception to these observations is
shown  in Table  4. Kansas attributed nearly all its
major lake problems to  natural conditions such as
low inflow and mineral intrusion that result in viola-
tions of the State dissolved oxygen and metal criteria.
Kansas measures use impairment based on its water
quality criteria, which do not reflect the agricultural
nonpoint source impacts on lakes. Additional infor-
mation showed that well over 50 percent of the total
number of lakes affected in Kansas could be traced
to agricultural runoff.
   Kentucky  also  considers natural  conditions
responsible for most of  the use impairment in that
State's lakes. This assessment reflects the release of
iron and manganese from the lake sediments under
anoxic  conditions.  Selenium-contaminated  lake
sediments are also responsible for use impairment in
North Carolina lakes; however, North Carolina con-
siders contaminated sediment a nonpoint source.
  Although States  use varying criteria to determine
whether a lake is maintaining its uses, most causes of
pollution in lakes are rooted in  nonpoint sources.
Even some pollutants identified as occurring natural-
ly or originating from specific causes, often can  be
controlled as nonpoint sources.
                                               PRECIPITATION   /
        -EVAPORATION
                  INFILTRATION

                  GROUND WATER FLOW

                  WATER TABLE
  SEEPAGE
Figure 3.—Hydrologic cycle.
                                                    BEDROCK
                                                13

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       Pollution  Control  and  Lake  Restoration
 Introduction

 The source of pollution to a lake will determine the ap-
 proach used to protect or restore lake uses.  Point
 sources are usually controlled through permit restric-
 tions on wastewater discharges. Nonpoint sources,
 because of their diffuse nature, are best controlled by
 effective watershed management. As point sources
 are brought under control in most areas, the impact of
 nonpoint sources becomes more visible and relevant.
   The 1986 305(b)  Water Quality Inventory found
 that 76 percent of use impairment in lakes resulted
 from nonpoint source pollution; this 1988 report con-
 firms that assessment, also finding 76 percent of the
 impairment caused by nonpoint sources. The 1988
 State data on which this report is based reflect, how-
 ever,  assessments of 63 percent more lakes than
 were surveyed for the 1986 Inventory.
   Once the sources of pollution have been success-
 fully addressed, in-lake restoration activities may be
 appropriate. Lake restoration works only when all
 parties concerned cooperate in its design and im-
 plementation.  In  developing restoration  plans for
 specific lakes, EPA Regions work with a number of
 State  and Federal agencies,  among them the  local
 Soil and Water Conservation District, the Agricultural
 Stabilization and Conservation Service County Com-
 mittee, the Soil Conservation Service, the U.S. Fish
and Wildlife Service, the U.S. Geological Survey, the
U.S. Army Corps of  Engineers, and any  other or-
ganization involved with lakes.
 Pollution Control

 • Point Sources. Over the past 20 years, the States
 have made great strides in controlling point sources
 of pollution through  National Pollutant Discharge
 Elimination System (NPDES) permits, State permits,
 construction of wastewater treatment facilities, and
 industrial pretreatment programs.
   Wastewaters from  cities, industries,  businesses,
 and  homes comprise a source of pollutants affecting
 lake water quality. Wastewaters receive  different
 treatment based  on the water quality needs of the
 receiving  stream. Treatment levels are generally
 referred to as primary, secondary, and advanced.
   Primary treatment  plants used by municipalities
 and  industry generally remove about 35 percent of
 pollutants on  the  average; secondary treatment
 around 85 percent. Neither primary nor secondary
 treatment removes phosphorus and nitrogen (which
 significantly affect lakes)  except as these  nutrients
 are attached to solids. Large cities and manufac-
 turers use advanced wastewater treatment  plants to
 remove these nutrients.
   Small-scale  systems, including septic  systems
 (which can also act as nonpoint  sources) may be
 used  by  communities  and  individual   property
 owners.  The effects of these small waste  disposal
 systems on water quality depend on their location:
the soil characteristics, groundwater tables, usage
conditions, and slope of the terrain.
                                             15

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   Effective operation and maintenance are key fac-
tors in assuring that waste disposal systems avoid
degrading water  quality. No matter how large or
small the system — whether it serves a city of millions
or a household of two — it must be properly installed
and operated, and maintained on a regular schedule.

• Nonpoint  Sources.  Daily, natural, and  routine
human activities - be they on the lakeshore or many
miles upstream in the watershed (the land that drains
into the lake) - contribute nutrients, sediment, and
other pollutants to a lake, principally as runoff from
streets,   construction  sites,  forests,  mines,   and
agricultural land. Effective control of nonpoint sour-
ces  could prevent  lake water  quality problems,
eliminating the need for costly restoration projects.
The  approaches that can be taken to reduce or
eliminate nonpoint source pollution are discussed in
the following paragraphs.
   Best management practices,  commonly referred
to as BMPs, are designed to prevent or reduce the
quantity of pollution entering a lake. BMPs have been
successfully applied to control the potential nonpoint
source pollution associated with many land uses, in-
cluding agriculture, silviculture,  construction, mini-
ng, and  urban activities. Among these BMPs are
conservation tillage, integrated  pest  management,
animal waste management, porous pavements, road
and skid trail management, land surface roughening,
stormwater management,  bank  stabilization  and
riprapping, lakeshore management, sedimentation
traps, runoff diversions, redesigned streets and park-
ing  lots,  and  detention/sedimentation   basins.
Knowledge developed by activities authorized under
Section 319 of the Water Quality Act will significantly
increase citizens' ability to control nonpoint sources
of pollution.  In addition, various Department of
Agriculture programs,  such  as the Conservation
Reserve Program, play an important role in address-
ing agricultural sources of lake pollution.
   A growing number of communities protect lakes
with regulations and ordinances that require BMPs to
prevent problems caused by erosion and pollution.
In the State of Washington,  for  example, the com-
munity of Mountlake Terrace regulates construction
to minimize its contribution to nonpoint source pollu-
tion. Where possible, planned development within a
lake's watershed can limit the entry of pollutants into
a lake.
   Pollution control  also is often brought about by
local opposition to activities that may degrade a lake,
prompting direct State or local agency intervention.
Throughout the Nation, citizens are forming lake as-
 sociations to protect, manage, and  restore their
 lakes.  These associations often promote local  or-
 dinances that restrict land use activities to control
 pollution. For example, Kentucky's mining regula-
 tions contain a petition process that allows land in a
 lake's watershed to be declared unsuitable for mini-
 ng. Such a petition process has been used to protect
 the water quality of Cannon Creek Lake in Kentucky.


 State Programs

 Several States have enacted legislation and set up
 lake management and nonpoint source pollution con-
 trol programs.  Although a few programs  have a
 regulatory component, they are predominantly volun-
 tary and  are based  on cost  sharing,  incentives
 promoting good land management, technical assis-
 tance, and information/education.
   South Dakota controls nonpoint source pollution
 through a combination of regulatory and voluntary
 measures that focus on their major nonpoint source
 problem:  agricultural  runoff.  The  South  Dakota
 Erosion and Damage Control Act regulates and per-
 mits "any land-disturbing activities within the  State
 which result in soil erosion and sediment damage."
 Also, the  State's Surface Water Quality Standards
 specify eight parameters that can be considered in-
 dices for nonpoint source pollution. Examples are (1)
 suspended solids likely to be  associated with  most
 agricultural  land-disturbing  activities,  (2) total dis-
 solved solids and conductivity associated principally
 with irrigation return flows, and (3) coliform bacteria
 associated with livestock operations. The State notes
 that its water quality standards are inadequate for
 documenting the impact of agricultural runoff.
   Slightly more  than  half  of the States use a
 regulatory approach to control pollution  through
 site-specific criteria and lake water quality standards.
 These  standards  are derived  largely  from  profes-
 sional judgement and literature values, with monitor-
 ing data also used. Washington, which  has long had
 standards, modified them in 1988 to establish both a
 site-specific nutrient (total phosphorus) criterion for
 Long Lake Reservoir and criteria for toxic substan-
 ces. Also, in 1988, Washington began taxing tobacco
 products to fund water pollution control  programs.
 Up to 20 percent of the $45 million generated  each
 year is earmarked  for nonpoint source  control;
 another 10 percent, for protection of lakes and rivers.
 In reality, lakes benefit from both funds because of
the close connection between lake water quality and
 nonpoint source pollution.
                                                16

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   Some States have established State lake manage-
 ment programs designed specifically to protect, en-
 hance,  and restore their lakes.  Among them are
 Maine,  Indiana, Illinois,  Massachusetts, New York,
 New  Jersey, South Dakota, Connecticut,  Florida,
 Minnesota, Idaho, North Dakota,  New Hampshire,
 Ohio, Wisconsin, North Carolina, and Michigan.
   The Illinois lake program is a good example of a
 comprehensive State lake  management program.
 The major program components include monitoring,
 lake classification to guide decisionmaking, develop-
 ment  and  implementation  of  lake/watershed
 management plansfor public lakes underthe Federal
 Clean Lakes Program, and education, technology
 transfer, technical assistance, and coordination.
   Since the program began in 1977, the Illinois En-
 vironmental Protection Agency (IEPA)  has compiled
 assessment information and baseline water quality
 and sediment  data  under Illinois' Ambient  Lake
 Monitoring Program  (ALMP).  The ALMP  defines
 trends  in  significant  lakes and  diagnoses  lake
 problems,  evaluates  progress in pollution  con-
 trol/restoration programs, and updates the State lake
 classification system.
   More than 700 volunteers have participated in
 monitoring 250 lakes under Illinois' Volunteer Lake
 Monitoring Program (VLMP), which, in addition to in-
 creasing citizen knowledge and encouraging local
 involvement, gathers fundamental information on the
 State's  lakes.  A  historic data baseline is being
 developed, as are lake protection and management
 plans.
   The IEPA has also developed a lake classifica-
 tion/needs assessment that can be used to establish
 protection, monitoring,  and technical assistance
 priorities, rank watershed land treatment projects,
 plan for recreational use, and screen candidates for
 Clean Lakes Program assistance.
   Educational and technical assistance to citizens,
 lake  managers,  and  local government officials
 promotes a better  understanding of  Illinois'  lake
 ecosystems  and  encourages  comprehensive
 management of these resources.
   Several States  have acted to reduce the precur-
sors of acid precipitation through  emission control
programs. For example, New York was the first State
to mandate reductions in emissions that contribute
to acid precipitation (State Acid Precipitation Control
Act, 1984).  The State is now proposing to formally
adopt the Federal New Source  Performance  Stand-
ards for emissions of oxides of nitrogen.
   Michigan has also  acted to reduce emissions.
From 1974-86, sulfur dioxide emissions from station-
 ary sources in the State were cut by 82 percent with
 all sulfate emissions standards met by 1987.
   Both New Hampshire and Vermont believe that
 reducing out-of-State emissions must be the first
 step in addressing the effects of acid precipitation in
 their States. Pointing out that 99.9 percent of the pol-
 lutants  responsible for the damage in the  State
 originate outside its borders, Vermont said that the
 problem will not be solved by treating the symptoms
 without treating the causes.
 Lake Restoration

 Lake restoration corrects lake  problems,  using
 ecologically sound principles to improve the lake on a
 long-term basis. To successfully restore lake water
 quality, the source of the problem must be identified
 and appropriate control measures then implemented.
   A lake problem is usually best controlled when ad-
 dressed   in  its  watershed  by  the  procedures
 described previously in this Report. After the sources
 of pollution have been eliminated or reduced to the
 appropriate level, some  in-lake measure such  as
 sediment removal can also restore water quality for
 long periods  of time. Others -  alum  treatment, for
 example, —  restore water quality on a short-term
 basis to  reduce loss of user days while watershed
 controls are being put in place. Unless the source of
 pollution is addressed, in-lake restoration efforts be-
 come repetitive and costly.
   Before restoration can begin, a thorough diagnos-
 tic study of the lake must be completed to determine
 the cause of  the problem, as well as the feasibility
 both of restoration itself and of the proposed restora-
 tion techniques. A technique that works  well for one
 lake may not be appropriate for another. The existing
 lake and watershed conditions  and characteristics
 are key factors in a successful  restoration project,
 and influence  the  potential  for improvement  in
 various lakes. In areas with high precipitation and
 easily erodible soils that contain excessive nutrients
 or organic materials, a lake can be improved only
 minimally, and will probably never be transparent and
 pristine. Therefore, the best attainable water quality
 should  be determined   before  deciding  on the
 feasibility of restoration and the appropriate restora-
 tion techniques.
   Restoration techniques for lakes continue to be
 developed. The  lake  restoration demonstration
 projects  in the  mid-1970s pioneered  many techni-
 ques that have since been refined. The principal res-
toration  techniques  briefly  described  here are
explained more fully in the Lake  and Reservoir Res-
toration Guidance Manual (LRRGM)  published by
                                               17

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 EPA in response to legislative mandate to compile in-
 formation about restoration techniques for public
 use. Further information on lake restoration will be
 available to the public in technical updates to the
 LRRGM.
    The States that have reported lake restoration ac-
 tivities are summarized  in  Table 5.  These  lake
 rehabilitation  techniques  are designed  to improve
 the lake; not all of them necessarily target the source
 of the problem.
    As mentioned previously in this Report, excessive
 nutrients and siltation caused significant impairment
 of use in lakes. Nutrient  input to  lakes encourage
 macrophyte growth and algal blooms. Also, as ex-
 plained  previously, the decomposition  process of
 algae and plants consumes oxygen, possibly lower-
 ing the dissolved oxygen  to a level that stresses or
 even  kills fish.  Sedimentation  may also stimulate
 algal and macrophyte growth by providing a suitable
 substrate for macrophytes and transporting  the
 necessary nutrients. Sediment input to  a lake can
 also reduce its depth - impeding boating and other
 water recreation.
   Because nutrients and  sedimentation have been
 recognized as major causes of lake use impairment,
 the  restoration techniques described in this Report
 focus  on abating their adverse effects, and  are
 presented according to the problems they cause.
 Also, as required by the legislation, techniques to
 mitigate the effects of acidity and toxics on lake water
 quality are discussed in this Report.
   Restoration techniques, therefore, are presented
 in the following categories (Table 6):
   1. Control of nuisance algae,
   2. Deepening to eliminate shaliowness,
   3. Removal of nuisance rooted vegetation,
   4. Improvement of fisheries,
   5. Acid mitigation,
   6. Toxics removal.
Control of Nuisance Algae

• Phosphorus  precipitation  and  inactivation:
Precipitation removes phosphorus from the water
column;  inactivation controls phosphorus release
from the sediments. Alum (aluminum sulfate) is most
frequently used because phosphorus binds tightly to
its salts under most conditions,  creating a floe that
settles out, leaving the water clear. If enough alum is
added, a layer of aluminum hydroxide will settle to the
bottom, preventing  phosphorus release. However,
 the lake should be deep enough to prevent resuspen-
 sion of sediments that precipitated via alum addition.
 This technique is most  effective  on  lakes where
 nutrient inflow  has been  diverted,  and has been
 proposed for both Delevan Lake, Wisconsin, and Hills
 Pond, Massachusetts.

 • Sediment removal: Controls nutrient release from
 sediments by removing the layer of the most highly
 enriched materials.  In this  procedure, a dredge
 (several types exist) loosens the sediment, which is
 then transported as a slurry through a  pipeline to a
 remote disposal area. Although the residue may (if it
 does not contain toxic material) be used as fill or fer-
 tilizer, the costs of dredge spoil disposal can be high.
 In small lakes, however, draining the lake and remov-
 ing sediments may be economically feasible. Sedi-
 ment removal can be effective, as demonstrated on
 Lilly Lake in Wisconsin and Lake Lansing, Michigan.
 Care must be taken in depositing the sediments, so as
 not to adversely affect adjacent wetlands.

 • Dilution and flushing: The nutrient concentration
 is lowered by introducing nutrient-poor water from
 another  source,  thus  starving  the algae.  Large
 amounts of additional water also can flush the algae
 from the lake faster than they can grow. This techni-
 que is limited by the availability of water from an out-
 side  source  and the rapid rate  of algal growth.
 Therefore, few examples  exist, with Moses Lake,
 Washington  being a notable exception.  At this lake,
 water from the Columbia River was diverted through
 the lake, producing dramatic improvement.

 • Biological controls:  Plant-eating fish and plant
 pathogenic organisms can be introduced into a lake
 to control nuisance aquatic vegetation. Grass carp, a
 non-native species originally imported from Malaysia
 in 1962,  can control, even eradicate plants  within
 several seasons. The Little Pond, Maine Clean Lakes
 Project successfully used this technique to control
 algal blooms. Six insect species imported by the U.S.
 Department of Agriculture under quarantine are being
 used  in the South to control alligatorweed and water
 hyacinth. The introduction of non-native species
 should be used with caution and with a comprehen-
 sive understanding of the native species/community
 interactions.  Significant negative environmental im-
 pacts, for example, reduction/elimination of native
 and/or desired species resulting from  over-competi-
tion of non-native species, are a possibility.

•  Aquatic macrophyte harvesting:  Vegetation is
mechanically  cut and removed from the lake. This
                                                18

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Table 5. - Lake rehabilitation technique
STATE
Cl
DE
FL
GA
IL
IN
IA
KS
ME
MD
MA
M
MN
M':
M;
H'J
NI
Nh
NJ
|S|V
ND
OH
OK
PA
Rl
SD
TX
VT
VA
W4
W,
NUTRIENT MANAGEMENT
X

X

X
X


X

X
X
X






X

X






X

X
PHOSPHORUS PRECIPITATION/INACTIVATION


X


X


X


X
X






X




X


X

X

SEDIMENT REMOVAL/DREDGING
X
X


X
X
X
X

X
X
X
X
X
X


X
X
X
X
X
X
X
X
X
X


X
X
DILUTION/FLUSHING
X

X

X
X


X



X






X









X
X
BIOLOGICAL CONTROLS


X




X



X
X








X




X


X

AQUATIC MACROPHYTE HARVESTING
X



X
X




X
X
X






X




X


X

X
X
ARTIFICIAL CIRCULATION




X
X




X
X







X

X






X

X
HYPOLIMNETIC AERATION




X
X

X
X






















FOOD CHAIN MANIPULATION


X








X
X



X













X
CHEMICAL CONTROLS
X



X



X

X

X




X
X





X


X

X
X
DIVERSION



X
X
X


X
X
X
X
X
X

X
X
X

X
X

X


X

X
X
X
X
SEDIMENT BASIN/TRAP



X
X
X



X
X
X
X

X

X

X
X

X
X


X


X

X
DRAWDOWN
X


X
X
X




X
X
X




X
X
X










X
SHADING/SEDIMENT COVER





X

























SEDIMENT OXIDATION











X



















HYPOLIMNETIC WITHDRAWAL
X




X




X
X
X







X










INTRODUCTION OF NON-NATIVE SPECIES








X






















states not listed in the table either did not report the information or reported in a way that was incons stent with the format of the table.
                  19

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                    Table 6. - Lake rehabilitation techniques by restoration objectives.
TECHNIQUE
Phosphorus Precipitation
Inactivation
Sediment Removal/Dredging
Dilution/Rushing
Biological Controls
Introduction of Non-Native Species
Aquatic Macrophyte Harvesting
Artificial Circulation
Hypolimnetic Aeration
Food Chain Manipulation
Chemical Controls
Diversion
Sediment Basin/Trap
Drawdown/Waterlevel
Management
Shading/Sediment Cover
Sediment Oxidation
Hypolimnetic Withdrawal
Nutrient Addition
CONTROL
NUISANCE
ALGAE
X
X
X
X

X
X
X
X
X
X



X
X

ELIMINATE
EXCESSIVE
SHALLOWNESS

X








X
X





REMOVE
ROOTED
PLANTS



X

X



X


X
X
X


IMPROVE
FISHERIES




X

X
X
X
X







ACID
MITIGATION




X




X


X



X
TOXICS
REMOVAL

X
X






X



X



procedure reduces the oxygen stress and fish kills as-
sociated with decaying vegetation. Harvesting also
increases open water and improves aesthetics. How-
ever, harvesting must be repeated regularly, and does
not completely address eutrophication over the long
term, because it  only reduces nutrient loading from
sediments and does not  eliminate external nutrient
loading to the lake. In some cases, such as Lake
Hopatcong, New Jersey, and Blackhawk Lake, Iowa,
it does remove significant amounts of nutrients. Har-
vesting may not be appropriate in some situations be-
cause it can stimulate growth and reproduction in
some plant species.
• Artificial  circulation: Circulation mixes the lake
waters, eliminating thermal stratification. It may con-
trol algal blooms by introducing dissolved oxygen to
the bottom, thereby  inhibiting phosphorus release
from the sediments. This technique has been used on
Hampton Manor Lake, New York.

• Hypolimnetic aeration: Not intended to destratify
the lake (as with artificial circulation), this procedure
brings cold hypolimnetic water to the surface of deep
lakes where  it is aerated by contact with the atmos-
phere and then returned to  the  hypolimnion. This
technique may be used to  maintain  a coldwater
                                                20

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fishery in a lake where the hypolimnion is normally
anoxic (oxygen-depleted), or to eliminate taste and
odor problems in drinking water withdrawn from a
cold hypolimnion. The Lake Como, Minnesota, Clean
Lakes Project is using this technique.

• Hypolimnetic withdrawal: Very little documenta-
tion exists on this procedure designed to withdraw
water from the deepest areas of a lake, which may be
extremely rich in nutrients. Spiritwood  Lake, South
Dakota, reduced algal blooms by removing nutrient-
rich water from the hypolimnion (in addition to im-
plementing  watershed  erosion  controls).  Lake
Warramaug, Connecticut, also has had  good results
using this technique.

• Food chain manipulation: Zooplankton grazing
might be used to control algae in the open water of a
lake or reservoir. This  requires analysis of the or-
ganisms that exist within the lake.

• Chemical controls: Perhaps the oldest and most
widely used method to manage weeds, herbicides
can rapidly reduce vegetation for periods of weeks to
months. Chemical control is not a long-term restora-
tion technique because  it does  not  address  the
causes of the problem, nor are nutrients and organic
matter removed from the lake. In fact,  nutrients se-
questered as plant biomass can be released back into
the water column as a result of decay of the plant
biomass. This can resuult in phytoplankton blooms.
Eola Lake in Florida is using this technique.

•  Diversion:  This method diverts nutrient-laden
water entering the lake into an alternative site, either a
treatment plant for waste disposal, or some form of
detention basin. The latter may be a settling facility or
a natural area such as a wetland. Sewage, septic tank
seepage,  and runoff  containing high  levels  of
nutrients are usually the waters targeted for diversion.


Deepening a Lake

•  Sedimentation basin:  Designed to hold  runoff
long enough for sediment to settle to the bottom of the
containment structure, sedimentation basins  are
positioned strategically in the watershed to trap the
runoff. This technique is both restorative and preven-
tive. Lake Tahoe in Nevada has used this technique.

•  Diversion: Described earlier as a technique for
removing nutrients, diversion also can be used to
prevent sediments from filling the lake. Diverted water
is  held in  a sedimentation basin for  settling long
enough for sediments to settle out.
•  Sediment removal (dredging): Also described in
a previous section, dredging is an effective technique
for deepening a lake and enhancing recreational ac-
tivities such as swimming,  boating,  etc. However, it
should be noted that the presence of some shallow
shoreline areas with aquatic macrophytes  is impor-
tant to the habitat and propagation of certain fish
species. In the restoration of a shallow lake a balance
between  the  maintenance and enhancement  of
recreational activities and fish habitat must be recog-
nized to ensure the overall health of the lake ecosys-
tem.
Control/Elimination of Nuisance Rooted
Vegetation

• Drawdown: Water is drawn from the lake to ex-
pose sediments to  prolonged freezing and drying
conditions that will kill plants. This procedure also al-
lows repair of dams and docks, sediment removal,
and other management practices. However,  some
plants are not affected by the exposure and in others
growth is stimulated. At most,  this technique should
be employed no more that every two years, to avoid
development of resistant weed species and damage
to benthic invertebrates. If the lake water level is con-
trolled by a dam, this is an inexpensive technique, al-
though costs will be associated with the loss  of the
use of the lake.

• Shading and sediment covers: Dyes can be ap-
plied to the water to limit light available for  plant
growth and sediments can be covered to stop such
growth. Sediment covers are most effective in small
areas where, if properly installed, they can completely
eliminate plants. Because  they are difficult to place
over growing plants, covers are best applied during
winter drawdown or early spring.

•  Sediment removal (dredging), biological con-
trols, macrophyte harvesting, and chemical con-
trols also  are  used to control  vegetation.  These
techniques were described previously.
 Improve Fisheries

 Many of the techniques previously described can be
 used to improve fisheries, with the selection of the
 specific technique dependent on the geographic area
 and characteristics of the lake. For example, in lake
 systems altered by  chemical  or  biological factors
                                                21

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(e.g., acidity), more acid-tolerant species may be in-
troduced.
  The most commonly used techniques to improve
fisheries  (all  described  previously)  include draw-
down, artificial circulation, food chain manipula-
tion,   hypolimnetic  aeration,  and   chemical
controls.
Acid Mitigation

Designed primarily to restore the aquatic ecosystem
to a pH level that ensures an adequate and healthy
fishery, restoration of an acidified lake involves two
basic strategies:
   1. Modification of the  physical and chemical
      environment, and
   2. Modification offish populations.
   The techniques selected  will depend upon the
geographic,  political, institutional,  and  economic
constraints within which the lake manager operates.
Many of the techniques involve liming and the use of
alkaline materials.

• Modification of the physical/chemical environ-
ment:  "Liming"  or  the  addition of other alkaline
materials is the most widely used technique for raising
the pH in lakes. Lime may be applied to the lake water
column,  lake sediments,  watershed,   or  feeder
streams.  Other less commonly used techniques to
mitigate high acidity in lakes are changing the land
cover,  managing  reservoir surges,  and adding
nutrients to alter the lake chemistry. Changing the
land  cover  involves eliminating   vegetation that
produces acidic litter (e.g., conifers). Reservoir water
drawdown and discharge can be altered to prevent
the acidic surge  that can occur with snow melt and
spring rains. Supplying nutrients to  a lake increases
its  biological  productivity,  thereby increasing the
lake's pH and acid neutralizing capability.

• Modification of fish populations: Five restoration
techniques are used to modify fish populations in
lakes affected by acidity. These include placing lime-
stone gravel in spawning beds,  stocking with adult
fish, stocking with acid-resistant fish, creating new
fisheries, and installing limestone filters in hatchery in-
takes.
   Four eastern States (Maryland, Maine, New York,
and Pennsylvania)  and  Michigan  described acid
mitigation efforts in the 1988 Lake Water Quality As-
sessments.  Maryland has been working extensively
over the past two years in an effort to control acidity
by liming streams and lakes.
   Approximately 200 surveyed Massachusetts lakes
either have been affected or are susceptible to acidic
inputs. Massachusetts has one State-funded  pro-
gram that addresses the issue: in the past two years,
this program has limed nine ponds. In June 1988, the
State  published  Acid Rain  in  Massachusetts, a
volume documenting the current status of the prob-
lem and the State's mitigation efforts to date.
   Pennsylvania, where State law prohibits discharge
of substances to State waters without approval, has
adopted  a policy of approving  the addition of
neutralizing  agents  only  as  part of  a  closely
monitored experimental  project designed to  study
the effectiveness and costs of liming.  Under this
policy, one lake (White Deer)  has been treated twice
with agricultural limestone (aglime).


Toxic Removal
Toxics may be present in a lake either in the water
column or in the sediment. The appropriate removal
technique depends on the location and nature of the
toxic  pollutants present. In general, techniques to
remove toxics from the water column include:

• Dilution/flushing. Dilution is the introduction of
toxic-free water that mixes with  the  contaminated
water and by thus reducing the relative concentration
of the toxics in the lake may minimize their adverse ef-
fects. Flushing the toxic-contaminated water from the
lake may improve the condition of the lake,  but may
also create a problem downstream.

• Chemical  treatment  and/or   pH  adjustment.
Under appropriate pH conditions  and/or upon treat-
ment with  particular  chemicals,  some toxics will
precipitate out of the water column and settle to the
bottom of the lake. Although this  removes the toxic
pollutants from the water column, it may result in a
problem with contaminated sediments.
   Removal  of toxic pollutants from bottom  sedi-
ments isthefocus of the five-year demonstration pro-
gram authorized  under Section  1l8(c)(3). Know-
ledge gained from this program should produce new
technology to control in-place pollutants. Current
techniques to remove or minimize the effects of con-
taminated lake sediments include:

• Dredging. The most commonly used method to
remove contaminated sediments from a lake  is by
dredging, which loosens the sediment and transports
it as a slurry through a pipeline to a remote disposal
                                                22

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areas. Since the dredge spoils are contaminated, the
disposal area must be completely contained so that
runoff will not recontaminate the lake, another area, or
leach into the groundwater. The physical action of
dredging may also resuspend toxics  in the water
column.

• Sediment covers. Contaminated sediments may
be covered with materials such as toxic-free sand,
gravel, or clay to protect the aquatic life from adverse
impacts of recycling toxics in the water column. How-
ever, unless the source of contamination is controlled
these covers will also become contaminated. Sheet-
ing material, such as a plastic-type liner that is resis-
tant to damage by the toxics present, may also be
used to line the bottom of the lake. However, these are
difficult to apply over large areas and may slip on
steep grades or float to the surface  after trapping
gases beneath them.
   Pollution  control  and lake restoration  are in-
separable: it is impossible to truly restore a lake on a
long-term basis without controlling the sources of
pollution to that water body. Some restoration techni-
ques (such as dredging and chemicals) work for the
short term, however, temporarily alleviating the prob-
lem  while the pollution is being  controlled. As the
States and their citizens become more aware and in-
volved in protecting and restoring their'lakes, they
are  realizing the need to thoroughly analyze the
lake's condition and the options for improving its
water quality before beginning  restoration proce-
dures.
                                                 23

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U.S. Environmental Protection Agency
Region 5, library (pi.. 12.0
77 West Jackson Boulevard, 12th floor
Chicago, II  60604-3590

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