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 ------- 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 ------- AT ------- Contents Foreword Executive Summary Problem Definition 1 3 5 Pollution Control and Lake Restoration 15 iii ------- 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. ------- 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 ------- 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. ------- 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 ------- 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 ------- 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 ------- 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. ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- 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 ------- (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 ------- 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 ------- U.S. Environmental Protection Agency Region 5, library (pi.. 12.0 77 West Jackson Boulevard, 12th floor Chicago, II 60604-3590 ------- |