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The State of Lakes in Maine

Lia d’Hemecourt, Brynna Patel, and Sophie Sarkar

Executive Summary

“The State of Lakes in Maine 2010” is the second chapter in The State of Maine’s Environment 2010, a report produced by the Environmental Policy Group in the Environmental Studies Program at Colby College in Waterville, Maine.  This is the sixth State of Maine’s Environment report published since 2004.

Lakes are a vital ecological, economic, and social resource for Maine.  On average, the water quality of Maine’s lakes is mesotrophic, and is comparatively better than lakes in other states.  Maine has 35 infestations of invasive aquatic plants, which is the least out of all New England states.  Consequently, Maine has the unique opportunity to prevent further spreading.  In total, lakes generate an estimated $2.5 billion annually in total direct expenditures, an amount equivalent to 5% of the state’s GDP.

At the same time, the water quality of Maine’s lakes is declining as a result of human and lake interaction.  Currently, all of Maine’s lakes are affected by mercury deposition from the atmosphere, and 30 lakes are further impacted by drawdowns or excess nutrients.  This is largely a result of the state’s industries, specifically agriculture and hydropower, as well as residential development.  Declining water quality impairs lake use and consequently decreases lake value.  Therefore, to sustain the benefits associated with lakes, the state and its localities should prioritize the protection of this important natural resource.


Maine has 5,785 lakes, which cover about a million acres of the state (Williams and Hill 2009).  Of this acreage, 97% is classified as great ponds, which are lakes over 10 acres if natural and 30 acres if manmade. Compared to other New England states, Maine has more lake acreage, better water quality, and fewer infestations of invasive aquatic plants (MDEP 2010b; USEPA 2010c; McPhredren 2010; CAES 2009; VTDEC 2010; Smagula 2010; RI DEM 2010).  As a result, lakes are an especially vital ecological, economic, and social resource for Maine.  The state’s clean lakes support healthy fish populations, provide suitable drinking water, generate money from tourism and property tax revenue, and are a primary location for recreation.  Currently, 64% of the state’s public drinking water comes from lakes, of which  58% is unfiltered because the water is clean enough to pass national drinking water standards (Tolman 2010).  Maine’s lakes also contribute to the state’s GDP and over 60% of Maine residents participate in lake-related recreational opportunities (Boyle, Scheutz, and Kahl 1997; MBPL 2009).

Figure 2.1 A spatial representation of the 5,785 lakes in Maine (MEGIS 2003)


Before colonization, Maine’s lakes were primarily used for fishing and transportation.  Some of the only known prehistoric sites of American Indians in Maine have been found near lakes, indicating that these early tribes depended on freshwater fish as a primary food source (Bourque 1995).  Additionally, many American Indian tribes, such as the Algonquin and Wawenoc, utilized Maine’s lakes and rivers as a transportation network; the tribes established a system of intricate canoe routes throughout inland and coastal Maine (Davistown Museum).  The 17th century marked the beginning of lake-related legislation.  Early European settlers created the Colony Ordinance of 1641-7, which established public access to any lake over 10 acres, known as a great pond (Stetson 1889). 

Industrial lake-use began in the 1800s.  Forestry brought coastal European settlers inland, and a waterway network was established to transport logs.  Within these waterways, lakes worked as storage areas from which logs would eventually be moved southward, towards mills (Hasbrouck 1995).  In the late 19th century, tourism became a more important part of the economy.  This transformation was paralleled by the increase in lake-related recreation and development.  Lake vacations for out-of-state visitors largely consisted of swimming, fishing, and canoeing.  Around this time, shoreline development increased and consisted mostly of large resorts and summer cottages.  Although Maine residents enjoyed the economic benefits associated with increased tourism, many felt that non-residents were exploiting their natural resource by overfishing  (Hasbrouck 1995; Wescott 1995). 

In the early 20th century, the number of lake resorts declined, largely as a result of fish scarcity, but the number of lakeshore properties increased as motorboat use became more common (Hasbrouck 1995).  Additionally, with the introduction of the automobile, many gravel roads were built to increase public access to lakes.  These roads are now one of the largest threats to lake health (Kallin 2010).  Today lakes are the basis for many of the state’s local economies.  Lakefront property values provide municipalities with year round tax revenue, and seasonal tourism continues to support local businesses.


This report seeks to compile and synthesize information about the lakes of Maine in order to create a comprehensive overview of their current state. First, we discuss the laws, institutions, and stakeholders that affect lakes. Then we examine some ecological aspects of lakes, specifically water quality and invasive aquatic plants, and evaluate how this compares to lakes across the US and New England.  Next, we discuss how lakes impact Maine’s economy, and, in turn, how industrial and residential development impact lakes. Then we examine some of the social aspects of Maine’s lakes, focusing on stakeholder engagement in lake stewardship.  Finally, we conclude with potential scenarios for how Maine’s lakes may change in the future and policy recommendations for how to preserve their health.


We reviewed government reports, books, journal articles, and documents issued by various lake organizations.  We also interviewed several lake experts at the Maine Congress of Lake Associations (MCoLA), the Maine Department of Environmental Protection (MDEP), the Bureau of Land and Water Quality (MBLWQ), and other lake associations. We gathered data from the MDEP Lake Water Quality Database, the last nine 303(d) lists published biannually by the MDEP, the PEARL Database, and reports published by the University of Maine Water Research Institute. We then graphed and analyzed this data using Microsoft excel.  In addition, we gathered spatial data from the Maine Office of GIS and the Atlas of Maine.  We used Geographic Information Systems (GIS) software to map the locations of invasive aquatic plants in Maine as well as the locations of impaired lakes in relation to some of the state’s major industries.

Laws and Institutions

Maine’s lakes are regulated by a number of federal and state laws.  National water quality standards in combination with state regulations on pollution, ecosystem preservation, and lakeshore development are used to manage lakes.  The laws relevant to our report can be divided into three categories: water quality standards, invasive aquatic plant management, and non-point source pollution regulation.

Table 2.2 The federal laws that regulate Maine’s lakes

Law Year Description Location
Federal Water Power Act 1920 Requires hydropower companies to obtain a license before damming a water body; overseen by the Federal Energy Regulatory Commission (FERC) USC Title 16 § 791-828c
Clean Water Act 1972 Establishes water quality standards to facilitate the protection and management of the nation’s water bodies; requires each state to create a 303(d) list of impaired waters; enforced by the EPA USC Title 33 §1251-1376
Endangered Species Act 1973 Lists and delists endangered species and facilitates their protection; Administered by the US Fish and Wildlife Services (USFWS) and the National Marine Fisheries Service USC Title 16 §1531-1544
Safe Drinking Water Act 1974 Establishes safe limits for contaminants in drinking water; outlines rules, schedules, and methods for water-testing and treatment; enforced by the EPA USC Title 42 §1400-1465

Table 2.3 The state laws that regulate Maine’s lakes

Law Year Description Location
Site Location of Development Law 1969 Mandates that all major development projects with potential to cause significant environmental damage be
approved by the Bureau of Land and Water Quality (BLWQ)
MRS Title 38 §481
Shoreline Zoning Law 1971 Mandates that municipalities issue zoning ordinances to govern where different types of development are permissible MRS Title 38 §435
Great Pond Law 1973 Grants public access to all water bodies classified as great ponds (lakes 10 acres of larger if natural and 30 acres or larger if man-made) MRS Title 38 §436-A
Maine Endangered Species Law 1975
Lists all endangered species in Maine and provides the basis for the Maine Endangered Species Program; overseen by the Commissioner of the Maine Department of Inland Fisheries and Wildlife MRS Title 12 §12803-12804
Standards for Classification of Lakes and Ponds Law 1985 Establishes all lakes as class GPA waters that must be suitable for multiple designated uses including drinking water, recreation, and aquatic habitat MRS Title 38 §465-A
Natural Resource Protection Act 1987 Requires permits to be obtained before  any development activities adjacent to areas of protected natural resources are undertaken MRS Title 38 §480-A
Waste Discharge Law 1989 Requires a permit to discharge pollutants into any aquatic ecosystem in Maine MRS Title 38 §413
Stormwater Management Law 1995 Requires that all new developments have a buffer between the water body and the development in order to decrease the amount of stormwater runoff into the water body MRS Title 38 §420-D
Erosion and Sedimentation Law 1995 Mandates that measures must be taken to minimize soil and sediment erosion resulting from development projects MRS Title 38 §420-C
Aquatic Nuisance Species Control Law 1997 Gives definitions of invasive aquatic plants (IAPs); mandates that MDEP take measures to increase public awareness about the threats associated with IAPs; gives MDEP permission to control IAP populations as deemed necessary MRS Title 38 §410-N
Prevention of the Spread of Invasive Aquatic Plants Law 1999 Prohibits the transport of all aquatic plants on the outside of vehicles or boating equipment on public roadways MRS Title 38 §419-C

Water Quality Standards

The Clean Water Act (1972), the Safe Drinking Water Act (1974), and the Standards for Classification of Lakes and Ponds Law (1985) establish water quality standards.  These standards classify surface waters, including lakes, by their designated uses.  In Maine the only classification for lake water quality is class GPA.  This establishes that lake water must be suitable for the following uses: drinking water supply, recreation in and on the water, aquatic habitat, fishing, agriculture, industrial process and cooling water supply, hydroelectric power generation, and navigation.  Additionally, class GPA waters must exhibit a stable or decreasing trophic state, defined by phosphorus, chlorophyll, or transparency measurements, and they must be free of reoccurring algal blooms (MRS Title 38 § 465-A 1985; USC Title 33 § 1251-1376 1972; USC Title 42 § 1400-1465 1974).

In fulfillment of sections 305(b) and 303(d) of the Clean Water Act and section 464.3 A of the State of Maine’s Water Classification Program, MDEP produces a statewide water quality assessment report every two years (USC Title 33 § 1251-1376 1972).  This assessment is designed to evaluate whether Maine’s surface waters are meeting the federal and state standards.  Both MDEP and the Lake Volunteer Monitoring Program (MLVMP) monitor, assess, and categorize the state’s lakes.  Lakes are designated into five categories (see table 2.3).  Category 4 and 5 lakes are lakes that are unable to fulfill their designated uses, and are considered to be “impaired” or “non-attainment”(MDEP 2010b).

Category 5 lakes are impaired by non-point source pollution, primarily phosphorus, and require a Total Maximum Daily Load (TMDL) report.  A TMDL estimates the amount of nutrients a lake can absorb without compromising water quality.  This is then used to determine land use policies to decrease runoff from development, forestry, roadways, and agriculture (Halliwell 2001).  Category 4 lakes are impaired but do not require a TMDL because they either already have one or are impaired by something other than pollution (such as a drawdown). The integrated water quality assessment report ends with a 303(d) list of all of the state’s impaired waters (MDEP 2010b).

Table 2.4 Attainment categories for the classification of lakes in Maine (MDEP 2010b)

Category Description Number of Lakes
1 Attains all designated uses and water quality standards 2,857
2 Attains some designated uses; no use threatened 2,892
3 Insufficient data and information to determine level of attainment 1
4 Impaired or threatened but does not require a TMDL report 29
5 Impaired or threatened by a pollutant; requires a TMDL report 1

Management of Invasive Aquatic Plants

There are two laws by which the state manages invasive aquatic plants (IAPs). The first is the Aquatic Nuisance Species Control Law (1997), which defines eleven aquatic plants as invasive to Maine. The law outlines how MDEP should educate the public on the threats associated with IAPs.  Lastly, the law delegates the power of monitoring and controlling the spread of IAPs to MDEP (MRS Title 38 § 410-N 1997).

Secondly, the Prevention of the Spread of Invasive Aquatic Plants Law (1999) prohibits the transport of any part of an aquatic plant on all public roadways; plant fragments must be removed from the outside of all cars, boat trailers, and boating equipment.  Additionally, the sale of IAPs is banned, and it is illegal to use an IAP in any way that could result in its introduction to a water body (MRS Title 38 § 419-C 1999).

Nonpoint-Source Pollution Regulation

There are a number of laws in Maine that seek to protect the integrity of aquatic ecosystems by managing development around water bodies. The laws below work to decrease the amount of nonpoint-source pollution from stormwater and erosion.

Development decreases the natural vegetative buffer along a shoreline, which in turn increases the amount of stormwater runoff. The Site Location of Development Law (1969) regulates the amount of stormwater that flows into lakes (MRS Title 38 §481 1969).  It is supplemented by the Stormwater Management Law (1995), which creates standards based on the nutrient composition of stormwater (MRS Title 38 §420-D 1995).  Under this law, MDEP is required to create a list of watersheds that are at risk of water quality impairment by current and potential development. This law also mandates that all new developments maintain riparian buffers along the shoreline. The National Resource Protection Act (1987) also recognizes the importance of buffers along shorelines. In 2001 the law was amended to regulate the removal of natural vegetation adjacent to water resources.  This law specifically states that lakes are a valuable aesthetic resource for Maine and their maintenance should be a priority (MRS Title 38 §480-A 1987).

In addition to stormwater runoff, erosion and sedimentation are also regulated by state laws. The Site Location of Development Law (1969) allocates the role of reviewing major development projects that may lead to erosion to MDEP  (MRS Title 38 §481 1969).  Similarly, the Shoreline Zoning Law (1971) regulates all types of development around lakes.  It requires that each municipality create a map of zoning ordinances to designate permissible activities in areas around lakes to  decrease erosion (MRS Title 38 §435 1971).  In conjunction with this law, the Erosion and Sedimentation Law (1995) requires that developers take measures to minimize erosion (MRS Title 38 §420-C 1995).


Maine has strong and progressive lake-related legislation.  However, the effectiveness of the laws is weakened by a lack of enforcement. This is in large part due to a shortage of funds available to MDEP. The Bureau of Land and Water Quality (BLWQ), which is the enforcement body of MDEP, has only three hired officials to enforce these laws.  Additionally, some of the strictest laws, like the Shoreline Zoning Law, are enforced by the local municipal governments. Often, municipalities hesitate to increase the stringency of standards, because more rigid standards could impede development and lead to a decrease in tax revenue (Bouchard 2010; Shannon 2010).


In Maine, lakes greater than 10 acres are considered a public good (MRS Title 38 §436-A 1973).  As a result, there are many stakeholders that affect the health of lake ecosystems in Maine. 

Government Bodies

The following government bodies have a stake in the enforcement of laws that protect Maine’s lakes. 

The Maine Department of Environmental Protection (MDEP)

The mission of MDEP is to prevent the degradation and pollution of the state’s natural resources, including its lakes.  The agency educates the public about threats to the environment and about how to engage in environmental stewardship.  MDEP also recommends legislation that will serve to protect the environment.  The Bureau of Land and Water Quality (BLWQ) is the enforcement body of MDEP; it protects and maintains Maine’s lakes and other water bodies through the enforcement of Maine laws.  BLWQ also provides information to the public about lake-related issues, threats to lakes, and lake protection initiatives (MDEP 2005a). 

The Department of Inland Fisheries and Wildlife (IF&W)

The Department of Inland Fisheries and Wildlife (IF&W) works for “the protection and enhancement of the state's inland fisheries and wildlife, while at the same time providing for the wise use of these resources”.  IF&W is responsible for creating and enforcing fishing regulations, issuing fishing licenses and permits, and educating the public about responsible fishing practices. The agency also stocks Maine's lake with fish, such as trout, for recreational purposes and strives to prevent the illegal stocking of non-native fish species that threaten the health of established fish populations (IF&W 2010).

Municipal Governments and Taxpayers

Municipal governments in Maine depend heavily on tax revenues from lakefront property owners; over 60% of municipal revenues are derived from property taxes (MDEP 2005c, 2005b).  Out-of-state residents often buy high-value second homes on lakes and pay high taxes on these properties.  Because they are only summer residents, they do not use public schools and other government-financed services.  These residents invest a considerable amount of money into the community without using many resources in return (Shannon 2010).Therefore, municipal governments have an interest in maintaining high property values around lakes by maintaining lake health (MDEP 2005c).

Municipalities in Maine each have their own democracy in which permanent residents vote on all of the town’s expenditures.  Since municipal boundaries are not consistent with watershed boundaries, all municipalities within a watershed must agree on an issue in order to create lake-wide policies.  This system also does not allow non-permanent or summer residents to vote.  Because their property taxes are often high, many of these part-time residents feel that they should have a say in how their tax dollars are spent (Shannon 2010).

Non-Governmental Organizations and Citizens’ Groups

Dozens of local and state-level lake associations and lake advocacy groups are active throughout Maine (Maine CoLA 2010).  The following are some of the largest groups with the greatest influence on lake-related issues. 

Maine Congress of Lakes Associations (Maine CoLA)

The Maine Congress of Lakes Associations (Maine CoLA) is a non-profit organization that seeks to improve and maintain the quality of lakes through community education and outreach programs. Their mission is “to promote the understanding, protection, and care of Maine’s lakes and watersheds”.  Maine CoLA fosters communication and information sharing between individuals and lake associations across the state by providing networking opportunities.  The organization raises public awareness about lake-related issues through various initiatives such as Project WET, which focuses on educating children and teachers.  Maine CoLA also provides technical assistance for its members working to monitor the health of their lakes or establish lake associations.  Maine CoLA is also an advocacy group.  Lobbying for legislation that benefits lakes is a large component of the organization’s activities (Maine CoLA 2010).

The Maine Volunteer Lake Monitoring Program (MVLMP)

The Maine Volunteer Lake Monitoring Program (MVLMP) is a non-profit citizen-based organization that trains and certifies volunteers to gather scientific data used to characterize the state of lakes in Maine (MVLMP 2010a). Founded in 1971 by MDEP, MVLMP is the oldest and largest organization of its type in the nation. It became an independent organization in 1992 but continues to receive financial and technical assistance from MDEP (Williams and Hill 2009).

Volunteers monitor the water quality of lakes and screen for the presence of invasive aquatic plants.  MVLMP volunteers have gathered both water quality and invasive aquatic plant data for hundreds of lakes in Maine (Williams and Hill 2009).  The findings are compiled into public documents that are provided to government agencies, municipalities, lake associations, and other interested organizations.  The data is also used to educate the public and raise awareness about threats to Maine’s lakes (MVLMP 2010a).


Many industries, such as water utilities and tourism, in Maine are heavily dependent on lakes.  In total, lakes support over 52,000 jobs in Maine (MDEP 2005c).  Water utilities rely on lakes; approximately 400,000 Maine residents use lakes for drinking water.  Clean lakes decrease the cost of providing public drinking water as cleaner water requires minimal to no treatment (MDEP 2005c).  Lakes also attract a large number of tourists to Maine.  Approximately 40 million people live within a day’s drive of Maine’s lakes.  Annually, over one billion dollars are generated from lake-related recreational tourism in the state, and 15% of that income comes from out-of state residents (MDEP 2005b).  Additionally, many industries, such as agriculture and hydropower, negatively impact lakes. Because they are not reliant on lake water quality, these industries have little incentive to engage in lake stewardship (MDEP 2010b).

The State of Lakes


The ecological state of lakes can be characterized by a number of chemical, biological, and physical factors.  First, we focus on the current state of water quality in Maine’s lakes, as measured by trophic status.  Second, we examine the causes and trends of lake impairment.  Lastly, we discuss the spread of invasive aquatic plants over time, and examine their impacts on lake health.

Water Quality

One way that water quality is defined is by trophic state. This is measured by secchi disk depth, total phosphorous, or chlorophyll concentration. There are four different trophic states: oligotrophic, mesotrophic, eutrophic, and hypereutrophic. Oliogtrophic lakes are clear and have sandy or rocky bottoms. They have minimal plant growth and high dissolved oxygen levels. Thus, they are able to support healthy fish populations and are the most suitable for recreational activities.  Eutrophic and hypereutrophic lakes are murky and have muddy bottoms.  They have a high amount of plant growth, which depletes dissolved oxygen (DO) levels and makes them unable to support many types of aquatic life. Eutrophic and hypereutrophic lakes have excess nutrients, are highly productive, and experience algal blooms.  Mesotrophic lakes are in a transitional stage between oligotrophic and eutrophic;  they are moderately clear and have medium nutrient and dissolved oxygen levels (MDEP 2010b; MVLMP 2010b, 2010a).

Table 2.5  Measurements used to determine the trophic state of a lake (MVLMP 2010b; USEPA 2010b)

Test Function Type of Test Measurements
Secchi Disk Reading Measures the clarity or transparency of the water Physical
Readings are taken at deepest part of the lake twice a month from May through October
Total Phosphorus Measures the level of both organic and inorganic phosphorus in solution and particulate form in the water Chemical
Samples are taken from a few inches below the water surface from early summer through end of October
Chlorophyll Concentration Measures the level of chlorophyll in water Physical/ Chemical Measurements taken throughout water column

Because it is the easiest and least expensive test to complete, MDEP and MVLMP primarily use secchi disk readings to determine trophic state. The secchi disk measures water clarity.  A high secchi disk depth indicates high water clarity, low trophic state, and high water quality.  The numerical guidelines used to define trophic status based on secchi disk readings are defined in table 2.6. 

Table 2.6  Numerical guidelines used to define trophic state based on secchi disk readings (MDEP 2010b)

Trophic state Secchi disk reading (meters)
Oligotrophic >8
Mesotrophic 4-8
Eutrophic 2-4
Hypereutrophic <2

The trend in Maine lake water quality from 1976-2006, measured by average secchi disk readings, is shown in figure 2.7.  The figure shows that while Maine lake water quality has fluctuated over the years, on average it has remained relatively constant within a mesotrophic range.  According to the 2010 Integrated Water Quality Assessment Report, approximately 7% of assessed lakes in Maine are oligotrophic, 58% are mesotrophic, and 35% are eutrophic.  In 2009 the USEPA surveyed a sample of lakes from each state to determine the overall water quality of lakes in the US.  According to this survey, approximately 16% of lakes are oligotrophic, 19% are mesotrophic, and 65% are either eutrophic or hypereutrophic . In combination, these results indicate that Maine lake water quality is comparatively better than the US (see Figure 2.8) (MDEP 2010b; USEPA 2010d).

Figure 2.7  The trend in the water quality of Maine’s lakes, measured by average secchi disk readings from 1976-2006 (Bacon 2006)

Figure 2.8  The trophic state of Maine’s assessed lakes compared to the US (USEPA 2010d; MDEP 2010b)

Impaired Lakes

Impaired lakes are those listed on the state’s 303(d) list required by the Clean Water Act (see Laws and Institutions).  This list is published biannually by MDEP in Maine’s Integrated Water Quality Assessment Report.  Currently, all of Maine’s lakes are impaired due to mercury deposition from the atmosphere, because mercury levels compromise fish consumption (MDEP 2010b).  As a result, MDEP recommends that adults and children eat no more than two freshwater fish meals a month.  Disregarding mercury content, 30 lakes, comprising approximately 84,319 lake acres, are considered impaired.  Of these 30 lakes, five have impaired aquatic habitats due to drawdowns in water levels, 23 are impaired by reoccurring algal blooms, and two are impaired due to deteriorating trophic status (MDEP 2010b).

Although drawdowns impair the most lake acres in Maine, algal blooms impair the largest number of lakes and are the primary reason for which lakes are listed (MDEP 2010b).  The majority of algal blooms are caused by phosphorus, which is a limiting nutrient in freshwater lakes.  Phosphorus comes from a variety of sources, including urban and agricultural run-off, commercial forestry, and commercial and residential land use (Halliwell 2001; MDEP 2010b).  Once a lake is declared impaired, the state and the impacted watershed district must develop a Total Maximum Daily Load (TMDL) report. Additionally, municipalities within the watershed are required to take action to reduce pollution.  For instance, their planning offices may tighten standards for site design and limit the allocation of stormwater permits.  The watersheds with impaired lakes are also more likely to be monitored, reviewed, and regulated by MDEP.  Lastly, these watersheds are more likely to receive funding from Section 319 of the Clean Water Act, which provides states with grants to address their nonpoint source (NPS) pollution problems (MDEP 2010b; Bouchard 2010).

Figure 2.9 A spatial representation of the 30 impaired lakes on Maine’s 303(d) list in relation to Maine’s major watersheds (MDEP 2010b; MEGIS 1990, 2003)

It is difficult to interpret the trend in the number of impaired lakes over time.  This is largely due to the “changing regulatory environment” (Bouchard 2010); changes in the number of lakes listed overtime often reflect shifting standards rather than decreasing eutrophication. Figure 2.8 shows all of the 303(d) impaired lakes in Maine since 1994.  The figure indicates a drastic increase in impaired lakes in 1996, followed by a drastic decrease in 1998.  These changes were not due to a pollution shock, but rather to the establishment of more rigorous selection guidelines.  Moreover, in 1998 MDEP began to change their guidelines from listing all blooming lakes to only listing lakes that had exhibited a history of repeated blooms during the five to ten years prior.  Additionally, before 1998, many lakes were listed because of downward trends in dissolved oxygen (DO) content.  Eventually MDEP decided to drop low DO levels as a cause of impairment due to a lack of consensus over how to differentiate between a naturally low level of DO versus a low level of DO due to human impact.  These two new selection guidelines have resulted in the steady decrease in impaired lakes since 1996 (Bouchard 2010).

Since 2002, the number of lakes impaired by algal blooms has remained relatively constant. For a lake to be removed from the list, it must exhibit normal coloration and be void of a summer time bloom for three out of five years (Bouchard 2010).  It is noteworthy that the same approximately 20 lakes have consistently bloomed since 1996.  This indicates that even with the implementation of stricter laws and TMDLs it is difficult to reverse the process of eutrophication in a lake.  In summary, the standards for attainment change relatively often to reflect better data and knowledge about lake systems. Therefore, the figure alone does not indicate a downward trend in eutrophication.  Instead, it demonstrates that water quality standards are subject to changes and that for the most part, changes in trophic status occur over long periods of time (Bouchard 2010; MDEP 1994, 1996, 1998, 2000, 2002, 2004a, 2006a, 2008b, 2010b)

Figure 2.10 The trend in lakes listed as impaired by algal blooms compared to all impaired lakes on Maine’s 303(d) list 1994-2010 (Bouchard 2010; MDEP 1994, 1996, 1998, 2000, 2002, 2004a, 2006a, 2008b, 2010b)

Invasive Aquatic Plants

Invasive aquatic plants (IAPs) pose a serious threat to Maine’s lakes (Williams and Hill 2009).  An IAP is any non-native aquatic plant species that has a negative impact on the area to which it is introduced (ITF 2002).  Infestations of IAPs in Maine’s lakes can have significant ecological, economic, and social impacts (Williams and Hill 2009).  These plants grow in dense beds that disrupt the ecological balance of a lake by out-competing native flora and fauna, reducing biodiversity, and increasing the rate of eutrophication (ITF 2002).  Lake-front property values decrease when a lake becomes overgrown with an IAP.  Additionally, the management and control of these plants once they are established is very expensive and resource intensive (Williams and Hill 2009).  Lake-related recreation is an important part of Maine’s culture, but IAPs threaten the quality of fishing, swimming, and other popular activities (ITF 2002).  Clear lakes are highly valued assets in Maine, and the influx of IAPs into the state is a direct hazard to the maintenance of these important natural resources (Williams and Hill 2009).

Infestations and Plant Varieties

Currently, there are five species of IAPs in Maine.  The presence of these species has been documented in 34 water bodies, 23 of which are lakes.  Two different species are present in Legion Pond bringing the total number of infestations to 35.  Of these 35 infestations, 31 have occurred in the past 10 years, and 19 of them are in lakes.  There were two documented infestations in the 1970s, zero in the 1980s, and two in the 1990s.  The remaining 31 infestations were identified in 2000 or later.  Figure 2.11 shows the progression of the spread of IAPs in Maine over four decades since the first infestation was documented in Sebago Lake in 1970. Figure 2.12 shows the cumulative rise in the number of infestations (McPhredren 2010).   

Figure 2.11  A series of maps showing the spread of invasive aquatic plants in Maine from 1970 to 2010 (McPhredren 2010; MEGIS 2003)

Figure 2.12  The trend in the spread of invasive aquatic plants in Maine from 1970 to 2010  (McPhredren 2010)

The five established IAP species are variable-leaf water milfoil (Myriophyllum heterophyllum), hydrilla (Hydrilla verticillata), Eurasian water milfoil (Myriophyllum spicatum L.), curly-leaf pondweed (Potamogeton crispus), and European naiad (Najas Minor).  There are also two documented infestations of a hybrid strain of variable-leaf water milfoil (McPhredren 2010).  Six other species pose imminent threats to Maine waters (PWD).  Though their presence has not yet been documented in Maine, these species are established in neighboring states, such as Massachusetts and New Hampshire, and in some bordering Canadian provinces (MDEP 2005d, 2005f).  They are Brazilian elodea (Egeria densa), fanwort (Cabomba caroliniana), frogbit (Hydrocharis morsus-ranae), parrot feather (Myriophyllum aqaticum), yellow floating heart (Nymphoides peltata), and water chestnut (Trapa natans) (PWD). 

Variable-leaf water milfoil is the most widespread IAP in Maine with 26 infestations (McPhredren 2010).  It grows in relatively shallow waters in very dense beds (UMCE 2004b).  Hydrilla, which is so far only present in two water bodies, is the most aggressive IAP established in Maine.  It “tolerates a wide range of environmental conditions including low light levels, high or low nutrient waters, and freezing temperatures”(MDEP 2005d).  Hydrilla can grow very rapidly; its stems can grow up to 30 feet in length  at a rate of one inch per day (MDEP 2005d; UMCE 2004a).  Like variable-leaf water milfoil, hydrilla forms dense mats of vegetation that block sunlight and increase nutrient levels in the water, thus accelerating the rate of eutrophication in a lake (UMCE 2004a).  Eurasian watermilfoil is also present in two waterbodies while curly-leaf pondweed and European naiad are each found in one water body (McPhredren 2010).  Table 2.13 summarizes some information about these five species.

Table 2.13 The five invasive aquatic plants present in Maine (MDEP 2005f; McPhredren 2010)

Name Year First Documented in Maine # of Infested Lakes/Ponds
Variable watermilfoil (Myriophyllum heterophyllum) 1970 26 (2 infestations are a hybrid form of Variable watermilfoil)
Hydrilla (Hydrilla verticillata) 2002 2
Eurasian watermilfoil (Myriophyllum spicatum L.) 2003 2
Curly-leaf Pondweed (Potamogeton crispus) 2004 1
European Naiad (Najas Minor) 2009 1
Mechanisms of Dispersal

IAPs can spread through several different means.  They can be dispersed through natural processes, but, most commonly, they are spread by humans (Bryson 2004).  One way that these plants propagate is through fragmentation.  A piece of a plant will break off and be transported to other areas by wind or water currents.  These fragments can also be transported to other water bodies by vectors such as animals, birds, or, most commonly, boats (RI DEM 2007).

One of the primary ways IAPs are transported from one water body to another is on boat propellers or other boating equipment.  Fragments of these plants become tangled around the propeller, and if not removed before the boat is launched into another water body, these fragments can take root and infest the new lake or pond (MDEP 2008a).  For species such as variable-leaf water milfoil, it only takes one plant fragment to infest a water body (UMCE 2004b).  Additionally, many plants can live out of the water for several days, so they can survive long periods of transport, increasing the risk of propagation (RI DEM 2007).

Tubers, dormant buds that grow off of plant stems either above or below ground, are another dispersal method.  These buds can remain dormant for years at the bottom of a lake.  Once they do begin to grow, the plants often develop very strong and complex roots systems that are difficult to eradicate.  One IAP that spreads primarily through this method is hydrilla (RI DEM 2007).

IAPs can also spread through seed dispersal.  Each year flowering plants produce seeds that scatter throughout a water body.  These seeds can be carried to new water bodies through the digestive tracts of birds and animals, resulting in new infestations.  Some of the seeds germinate the following spring but many remain dormant for up to ten years.  The seeds that do not germinate form a back-up seed supply and guarantee reproduction of the plant in the future (RI DEM 2007).

Control of Established Populations

Once IAPs are established, they are extremely difficult to eradicate.  IAP populations require constant attention and management.  If a species is successfully eradicated, the infested water body must be monitored for potential recurrences.  There are various chemical, biological, and physical control methods available for use in suppression and eradication efforts (Bailey 2008).  Only physical and chemical controls have been implemented in Maine (MDEP 2008a).

Three of the most widely implemented physical management techniques are hand-picking, cutting, and the use of benthic mats.  One study conducted by Bailey et al.  (2008) compared the effectiveness of these three techniques in controlling variable-leaf water milfoil in Maine lakes.  The study found that the best physical management plan for a lake depends on the nature of the infestation.  While all three methods were effective in lowering plant re-growth, it was found that each method has drawbacks. 

Hand-picking, which involves using scuba gear to dive to the bottom of a lake to remove each plant by its root system, is low-cost but time and labor intensive.  Cutting, a method that entails diving down and cutting each plant at the base of its stem, is also inexpensive.  However, it is even more time and labor intensive than hand-picking thus rendering it an inefficient control method.  The use of benthic mats, or installing mats of specially-formulated fabric over invasive populations for extended time periods, is the least time-consuming method but also the most expensive.  The study concluded that benthic mats are the best physical management technique for areas with dense growth spanning large areas.  Alternatively, they found that hand-picking is a more appropriate control measure for infestations that are less dense and occur in a concentrated area (Bailey 2008). 

Physical management techniques are the most frequently implemented in Maine to control IAP populations.  As of 2008, the DEP has given about $60,000 in grants to support volunteers in the implementation of manual removal techniques in ten water bodies.  Some lake associations have also begun using diver-assisted suction harvesting (DASH) machines, which are a kind of vacuum, to remove invasive aquatic plant species (MDEP 2008a).

Chemical controls, namely herbicides, are used infrequently in Maine (MDEP 2008a).  Herbicides have the potential to destroy the root systems of these plants, thus minimizing future growth (MDEP 2005d).  However, they can also be harmful to humans and native flora and fauna, persist in the environment, bio-accumulate, and pose other risks, so the DEP has limited their use in managing IAPs (MDEP 2008a).  Some plants, such as hydrilla, can become resistant to herbicides, making long-term chemical management plans impractical (Bailey 2008). 

The DEP has used herbicides in only four water bodies in Maine to control IAP populations.  All of these water bodies are lakes.  Two of these treatments, in Damariscotta Lake and Pickerel Pond, were for hydrilla infestations, and the two others, in Salmon Lake and Pleasant Hill Pond, were for Eurasian water milfoil infestations (Baldacci 2009, 2010; MDEP 2008a).  In one of the treated water bodies, Pickerel Pond, the use of the herbicide fluridone has reduced a hydrilla infestation by about 95% (MDEP 2005d, 2005f).

Prevention of the Spread of IAPs

Preventing the spread of IAPs is easier and less expensive than controlling populations once they have been established.  A University of Maine Cooperative Extension report states that “the best way to control…any aquatic invader is to prevent it from being introduced in the first place” (UMCE 2004b).  MDEP, in partnership with the Maine Volunteer Lake Monitoring Program and other associations, has taken numerous actions to try to stop the spread of invasive species (MDEP 2008a; Williams and Hill 2009).

MDEP has started initiatives such as the Courtesy Boat Inspection (CBI) program, which was initiated in 2000.  Trained volunteers inspect boats entering and leaving water bodies for invasive plant matter and educate boaters about the threats associated with IAPs.  Maine COLA and the Lakes Environmental Association train these volunteers to become inspectors.  In 2009 alone, 57,522 inspections were conducted, 1,849 of which found plant fragments.  Thirty of those fragments were IAPs that were intercepted before they could have entered a water body.  Additionally, 254 of the fragments were IAPs found on boats exiting a water body.  These finds could have prevented these fragments from entering another water body at a different launch site.  MDEP funds some local CBI programs with money acquired from the sale of a “Lake and River Protection Sticker” required for all registered watercraft operating in inland Maine (MDEP 2009).

MDEP has partnered with the Maine Turnpike Authority and the Maine Department of Transportation to place signs along all major roadways crossing into the state, as required by the Aquatic nuisance species control law.  The signs inform drivers that the transport of all aquatic plants is prohibited on public roadways in Maine. Additionally, the MDEP is required to place signs at all state freshwater boat launches to warn boaters that all boating equipment must be free of aquatic plant matter.  The law mandates that these signs be installed at other popular boat launch sites “as available funds allow” (USC Title 38 § 410-N 1997).  MDEP also places signs at boat launch sites on infested lakes to inform the public of the infestations (MDEP 2008a).

Additionally, MDEP has closed or limited use of boat launch sites on some infested water bodies in an attempt to minimize the risk of transport of IAP fragments from these water bodies to new water bodies.  The use of one launch site on a highly infested water body off of Route 27 has been limited.  Boat trailers are now prohibited at this site; boats are only allowed to be carried in and out of the water.  This lowers the risk of bringing IAP fragments into or out of the lake (MDEP 2008a).

Effectiveness of Prevention Measures

Compared to other New England states, Maine has been effective at minimizing the spread of IAPs.  As figure 2.14 shows, Maine has the lowest percentage of lakes infested with IAPs; only 0.6% of Maine’s lakes have infestations (McPhredren 2010; Williams and Hill 2009).  Rhode Island has the highest percentage of infested lakes: 15.6% (RI DEM 2010; RI HTL 2010).  Vermont, New Hampshire, and Connecticut have the second, third, and fourth highest percentages, respectively (VTDEC 2010, 2003; Smagula 2010; NHDES 2008; CAES 2009; CTDEP 2010). Data were not available for Massachusetts. 

Figure 2.14 The percentage of total lakes infested with invasive aquatic plants in Maine compared to other New England states (VTDEC 2010, 2003; Smagula 2010; NHDES 2008; CAES 2009; CTDEP 2010; RI DEM 2010; RI HTL 2010; Williams and Hill 2009; McPhredren 2010)

Maine also has the lowest number of lakes infested with IAPs, as is shown in figure 2.15.  Only 23 of Maine’s lakes have infestations (McPhredren 2010), compared to 100 in Connecticut  (CAES 2009), 66 in both Vermont and New Hampshire (VTDEC 2010, Smagula 2010), and 40 in Rhode Island (RI DEM 2010). Again, data were not available for Massachusetts.

Figure 2.15 The number of lakes infested with invasive aquatic plants in Maine compared to other New England states (VTDEC 2010, Smagula 2010, CAES 2009, RI DEM 2010, McPhedren 2010)

Between 2000 and 2004, 23 new infestations were documented in Maine.  However, between 2005 and 2010, only eight new infestations were found (McPhredren 2010).   The considerable decline in the rate of spreading, shown in figure 2.16, suggests that the measures that have been implemented by MDEP and other organizations to prevent the spread of IAPs have been effective. 

Figure 2.16  The number of invasive aquatic plant infestations documented each year 1970-2010 in Maine (McPhredren 2010)

Non-Native Fish Species

The costs of controlling invasive species are not limited to plants.  Invasive aquatic fish pose a growing threat to the health of the aquatic ecosystems in Maine as people transport them from one lake to another. 

There are a total of 67 varieties of fish in Maine’s waterways and only 70% of which are considered to be native (TNC 2009).  Although the number of introduced species in Maine is relatively low when compared to other areas in the United States (TNC 2009), the number is increasing.  The DIFW currently stocks lakes with sport fish, such as trout, but illegal fish stocking is becoming a more prevalent issue as people transport fish from one lake to another, acting as “bucket biologists” (Bowley 2009). 

Introduced fish species fall into three categories.  First, non-native to North America, second, non-native to Maine, and third, native to Maine but non-native to the specific water body.  Common introduced fish include: large and smallmouth bass, northern pike, black crappie, white and yellow perch, rainbow smelt, white sucker, and a variety of minnow species commonly used as bait (MDIFW 2010). 

Fish stocking first began in Maine about a hundred years ago as a way to improve the fishing in the state.  However, whether legal, illegal, or accidental, the spread of non-native fish types throughout the waters in Maine is increasing, causing detriment to the native wildlife populations of the infested waters.  For example, since 1945, the amount of largemouth bass in lakes has increased by six fold, and the amount of white suckers has increased by over 90% (TNC 2009).  From 2005 to 2007, the DIFW documented fifty new cases of introduced fish species (TNC 2009).  This trend is devastating the biodiversity of the freshwater ecosystems in Maine (MDIFW 2010).  As biodiversity is lost, ecosystem stability is compromised and thus the health of entire ecosystems is harmed.  Introduced fish outcompete the native fish species, thereby potentially eliminating entire populations from lakes.

Illegal fish stocking is also a problem for the fishless ponds of Maine.  Fishless ponds provide for homes for a variety of organisms, such as damselflies and salamanders (Carpenter 2009).  However, these species only thrive in locations where fish are absent.  The introduction of fish therefore harms the ability of these organisms to survive.  In a report done for the DIFW by Cynthia Loftin of the University of Maine, it was estimated that out of the 107 lakes that were historically fishless in Maine, over half are now contain fish (Carpenter 2009). 

Moreover, the removal of an introduced species from a lake is an expensive and arduous process.  Big Reed Pond, in Piscquatis County, is home to a genetically unique population of Artic char, and it is one of the only twelve lakes in Maine to contain the species.  However, since rainbow smelt and creek chub were introduced to the lake in the 1990s, the native population of char has decrease significantly.  This is because the char are forced to compete with the alien fish for food resources and young char have become prey for these fish.  Ecologically, since the smelt were introduced, the water quality has significantly declined (MDIFW 2009).  Also, the eradication of a non-native fish species is impossible to do without affecting the other life forms within the aquatic ecosystem.  Further, the eradication of the introduced species comes at a high economic cost.  To carry out an initiative to remove the smelt and chub from Big Reed Pond, rotenone, an organic compound that is lethal to fish, was used after all non-target fish were removed (Holyoke 2010).  On top of this, in June of 2010, eight of the char were airlifted to a fishery so as to provide a safe habitat in which they could procreate (Carpenter 2010).


Maine’s lakes are one of its most important natural resources.  Lakes add tremendous value to the state’s economy through recreation, property values, drinking water, and commercial use.  Additionally, since lakes are not confined to a specific region, the economic benefits are shared throughout the state; while many lakes in southwestern Maine are used for recreation and generate copious tourism dollars, other lakes in western Maine are dammed for hydropower generation.  At the same time, economic growth can negatively impact lakes.  In fact, many of the industries and residents who profit from lake-use are also responsible for lake impairment (MDEP 2010b).  This can be described by a feed-back system where the failure to protect water quality results in decreasing lake-use, and in turn, decreasing economic value (Perrings, Dalmazzone, and Williamson 2000).

Value of Lakes

Boyle et al. (1997) conducted the only available comprehensive economic valuation of Great Ponds in Maine, estimating the value of significant lakes based on direct expenditures.  Specifically, the authors estimated the amount of money spent on lake recreation, lake-front property investment and tax revenue, drinking water, and commercial lake use (Boyle, Scheutz, and Kahl 1997).  In combination, these estimates illustrate the aggregate effect of lakes on the state’s economy.

Table 2.17  The total annual direct expenditures on Maine’s significant lakes in billions of 2010 dollars (Boyle, Scheutz, and Kahl 1997; USBLS 2010)

Use Resident Non-Resident All Users % of GDP
Recreation 1.285 0.220 1.505 3
Lakefront property tax revenue 0.363 0.121 0.484 1
Other uses 0.263 0.032 0.543 1
Total direct expenditures 1.912 0.373 2.532 5

Given the lack of a recent statewide valuation of Maine’s lakes, we adjusted the data from the Boyle et al. (1997) study to describe the current economic impact of lakes.  First, we converted  the values from 1996 dollars to 2010 dollars using the US Bureau of Labor Statistic’s inflation calculator (USBLS 2010).  In so doing, we were able to compare the value of lakes to more recent economic data available for other Maine industries. Additionally, we assumed that aggregate state trends in housing and recreation over the last ten years could be extrapolated to lake regions.  Under this assumption, the value of lakes estimated in Boyle et al. (1997), even after accounting for inflation, underestimate the value of Maine’s lakes in 2010 for three reasons: the increase in housing development and property values, tourism, and recreation from the time of the study to present (MBPL 2009; USCB 2000a, 2009).  We describe the three features in more detail below.

Following the national trend, Maine has experienced a net increase in housing development and property values since 2000.  The number of housing units in the state increased by approximately 8% from 651,901 in 2000 to 704,574 in 2009. Additionally, after adjusting for inflation, the median value of owner-occupied housing units increased by approximately 44% from $122,966 in 2000 to $177,500 in 2009 (USCB 2000a, 2009).  There also has been an upward trend in many lake-related recreational activities, including kayaking, canoeing, and fish photography, from 1995 to 2009.  The number of fishing licenses sold has also increased by approximately 20,000 or 7.4%, during the same time period.  Lake and pond swimming also remains one of the most popular recreational activities in the state, with approximately 64.4% of residents participating.  The increased participation in some lake-related recreational activities combined with the sustained popularity of others should reflect a net increase in direct lake recreational expenditures from 1997 to 2010 (MBPL 2009; MDEP 2005c).

Given these assumptions, we used the 1997 valuation as a low estimate of the current economic impact of lakes in Maine.  After adjusting for inflation, the study estimates that Great Ponds contribute approximately $2.5 billion annually in total direct expenditures to the state’s economy.  This amount is equivalent to about 5% of Maine’s 2008 gross domestic product (GDP) of $49.7 billion (BEA 2008).  The percentage demonstrates the importance of lakes to Maine’s economy.  Figure 2.17 compares the lake industry to some of the largest commercial sectors that make up Maine’s GDP.  The direct expenditures generated from lakes are comparable to the billions generated from the wholesale trade and technical services industries.  Using total direct expenditures, if lakes were considered a sector on their own, they would rank eighth in terms of contribution to the state’s GDP (Boyle, Scheutz, and Kahl 1997; BEA 2008).  One problem with this comparison, however, is that direct expenditures on lakes may be endogenous in the values of the other commercial sectors.  For example, some of the money generated from the construction or accommodation sectors may include expenditures on lake-front property construction or lake-related recreation.  In other words, these expenditures would be counted multiple times.  Therefore, a better comparison is the economic impact of lakes to other natural resource industries in Maine (see figure 2.18).

Figure 2.18  The total direct expenditures on lakes compared to other industries that contribute to Maine’s GDP in billions of 2008 dollars (BEA 2008; Boyle, Scheutz, and Kahl 1997)

In the comparison of total direct expenditures in the forest, ocean, state park, and lake industries, lakes come in second to forests (NOEP 2004; Morris, Roper, and Allen 2006; NESFA 2007).  Although total direct expenditures on forests are nearly three times more than on lakes, the marginal direct expenditure is higher for lakes.  Since there are about 19 times more forest acres than lake acres in Maine, per acre direct expenditures in lake use are much larger, at about $2,540 per acre, compared to $414 spent per forest acre.  These marginal direct expenditures may be useful for assessing the potential costs and benefits of lake conservation. Moreover, the money generated from logging an acre of forest near a lake, may not be worth the potential impairment of the lake, which is associated with more value per acre (Boyle, Scheutz, and Kahl 1997; NESFA 2007).

Additionally, lakes generate more money through recreational expenditures than any of the other natural resource industries compared in this study. Out of the total direct expenditures on lakes, over half is generated through recreation. The $373 million generated by non-residents can be used to proxy for out-of-state tourism funds. This value makes up approximately 4% of the $10.1 billion in goods and services generated by tourism, Maine’s largest industry (MBPL 2009).

Figure 2.19  The total direct expenditures on all lake uses, including recreation, compared to other natural resource industries in billions of 2010 dollars in Maine  (NESFA 2007; NOEP 2004; Morris, Roper, and Allen 2006)

Lastly, over $1 billion is generated from lake uses other than recreation.  This number is largely comprised of drinking water supply and property tax revenue.  Lakes provide the state with about 64% of its public drinking water, worth approximately $192 million.  Consequently, the high water quality of many of Maine’s lakes saves the state from spending money on developing new filtration plants (Boyle, Scheutz, and Kahl 1997; Tolman 2010).  Additionally, lake-front property provides the state with over $424 million in property investment and tax revenue.  As mentioned above, it is likely that this is a low estimate given the increase in housing units and property values since the time of the study (Boyle, Scheutz, and Kahl 1997; USCB 2000a, 2009)

Residential Development, Industry, and Lake Impairment

Given the considerable economic value of Maine’s lakes, their preservation should be a top priority for the state and its residents. However, many of the residents and industries who profit from lakes also contribute to their impairment. Impairment here is defined as lakes listed on the 303(d) list for not attaining one or more of their designated uses (see water quality). Specifically, impaired lakes either suffer from water level drawdowns, declining trophic status, or algal blooms. The former impairment is related to dams, and the latter two are related to pollution.

Figure 2.20  The acres of Maine’s lakes in 2010 impaired by source in thousands (MDEP 2010b)

By acreage, the three leading sources of lake impairment are hydrostructural flow modifications (dam construction and operation), residential districts, and agriculture.  All of these sources are human related. Furthermore, the data indicate that lake impairment is specifically related to industrial and residential development (MDEP 2010b). The relationship between residential development, industry, and impaired lakes is illustrated spatially by figures 2.21, 2.22, and 2.23.

Five of the 30 impaired lakes, comprising 48,964 acres, are impaired due to drawdowns, which affect the aquatic habitat use of lakes. The term “drawdown” specifically refers to the downward manipulation of water levels as a result of damming a lake or the streams and rivers to which it is connected (MDEP 2010b). Three of the five lakes impaired by drawdowns are located in the high elevations of the Northwest where there is greater hydropower potential. All of the five lakes are located near a dam used for hydropower generation. Many of Maine’s streams, rivers, and lakes are dammed to provide the state with hydroelectric power, which makes up approximately 30% of the state’s energy generation (SMPUC 2009). However, the benefits of hydropower generation on or near lakes come at the cost of over 48,000 acres of impaired aquatic habitat. This is an example of how an industry that benefits from lake water may also be a leading source of lake ecosystem impairment (MDEP 2010b).

Figure 2.21  The spatial representation of impaired lakes compared to hydropower potential, measured by elevation, and the location of nearby hydropower dams in Maine (MDEP 2010b; MEGIS 2004)

The 25 lakes impaired by pollution are concentrated in the southeastern and northern Presque Isle regions of Maine.  According to the 2010 draft Integrated Water Quality Assessment Report, 22,655 lake acres are impaired by agriculture and 35,477 lake acres are impaired by residential districts.  In figure 2.22, agricultural intensity is measured by cropland density, the percentage of land covered by crops and pasture within a 2.5 km radius of any point. In figure 2.23., residential development is measured by population density, the number of people per acre of land. These figures illustrate the spatial relationship between areas afflicted with impaired lakes and areas with high levels of agriculture and population. The southeast region of the state, which has both a high population density and cropland density, is the location of 57% of the state’s impaired lakes. Northern Aroostook County, which has high cropland density, is the location of 23% of impaired lakes (Ambrogi 2009; MDEP 2010b; MEGIS 2004; USCB 2000b).

Figure 2.22 The spatial representation of impaired lakes compared to the level of agriculture measured by cropland density in Maine (Ambrogi 2009; MDEP 2010b)

Figure 2.23 The spatial representation of impaired lakes compared to the level of residential development measured by population density in Maine (MDEP 2010b; USCB 2000b)

The three maps in combination imply a strong relationship between industry, specifically hydropower and agriculture, population density, and lake impairment. Moreover, the economic benefits that lakes provide to property owners and water-reliant industries often come at the cost of declining water quality (Boyle et al. 1998; Gibbs et al. 2002).


Maine’s lakes have proven vital to cultural development through recreation and the creation of livelihoods. In 2000, MDEP conducted a survey of stakeholders in about 138 lakes in Maine, with 614 surveys returned.  On average, survey respondents had been visiting or living on their lake for 32 years. The respondents felt that the lake was an integral part of their life (MDEP 2001). Moreover, a 2009 report issued by the state government found that almost 65% of Maine residents swim in lakes as a common outdoor activity and nearly 60% participate in boating.  Fishing is the third most common outdoor recreation activity in Maine. Furthermore, Maine’s economy relies heavily on the health of the state’s natural resources, as recreation-based tourism is a key sector of the economy. Tourism is now Maine’s largest industry, employing 140,000 people, earning $425 million in tax revenue, and bringing over $10 billion into the state annually  (MBPL 2009).  However, changes in lake ecosystems because of human action are threatening the health of the lakes of Maine.

Private Home Development and Lake Water Quality Degradation in Maine

As lakes age, they naturally accumulate sediments and move from oligotrophic to eutrophic. However, when this change is accelerated by human activity, it is becomes an issue of cultural eutrophication (MDEP 2006b). As this pertains to Maine, gravel or unpaved roads and exposed shorelines of lakefront houses increase the ability of rainwater to carry nutrients directly into a lake.  The increase in nutrients causes algal blooms, which in turn decreases the amount of available oxygen in a lake. Fish, such as Maine’s salmon and trout, cannot survive in eutrophic lakes.

In 1972, the Clean Water Act created standards that were to be met within twenty years on the quality of fishable and swimmable water. However, these goals were not attained in Maine. Scientists originally thought this was due to lake water pollution from large industrial effluent, but in the late 1980s they began to realize that this was in primarily due to the poor drainage of residential areas, or non-point source pollution (MBLWQ 2005a).

Shoreline Development

A developed watershed with 40% forest cover and 60% development increases the amount of phosphorous able to enter a lake by 720% as compared to a completely undeveloped shoreline (Dudiak). This is in large part due to the estimated 40 to 60% of rain that runs off of lawns into lakes rather than being absorbed into the soil (MBLWQ 2005a).  Once the process of eutrophication begins, a chemical change occurs within the lake that results in the release of more phosphorous from the sediment, which perpetuates the algal bloom cycle  (MDEP 2006b).


Sixty five percent of Maine roads are private camp roads (Shannon, 2010) and many of them were constructed before the 1960s, when much of the private lakefront home development in Maine occurred (Dudiak). Due to their poor condition, the roads funnel rain water directly into lakes. As the water flows across the dirt and gravel roads, it acquires and increased amount of particles and nutrients.


Erosion is harmful to lake health because it disrupts natural habitat. It has been shown to irritate the gills of fish as well as destroy their breeding grounds. Erosion also leads to algal blooms and erases much of the shoreline around lakes.

In 2008 MDEP reported the major threats to the lakes of Maine and found the most serious threat to be erosion. Fifty eight percent of erosion was due to development and landscaping around residential areas, 20% was due to private roads and driveways, 11% was due to state and town roads, and 11% was due to other causes such as logging (MDEP 2008d).

According to the National Lakes Assessment of 2010, lakes with poor lakeshore habitat are three times as likely to be in poor biological condition as those with a healthy lakeshore habitat (USEPA 2010b). This is defined by healthy vegetation and natural buffers along the water’s edge. Additionally, lakes with high nutrient levels, namely nitrogen and phosphorous, are two and a half times more likely to be in poor biological health than those with lower levels of these nutrients. Therefore, when looking at how to minimize human impact on lakes, best management practices of development must be implemented.

Best Management Practices

Best management practices (BMPs) include a variety of actions, but the main focus is to decrease the amount of stormwater runoff into lakes. Ways in which this can be executed include: the maintenance of a buffer of natural trees and shrubs between the home and the water, the creation of gardens to help absorb rain, the repaving of roads with a porous pavement, the maintenance of septic systems, and the minimization or elimination of fertilizer and pesticide use (MBLWQ 2005a).

Separating, understanding, and mitigating factors that negatively impact watershed health is a complex process.  Each watershed in Maine and the number of water bodies of which it is comprised have unique characteristics. They therefore require individual attention when forming sustainability and restoration plans (USEPA 2010b, 2010a).  The physical characteristics of the lake coupled with its location and climate all work to dictate water quality.  However, despite these variations, human actions play a major role in determining water quality (Maine CoLA 2010).  It is therefore important to use best management practices when living within a lake ecosystem. 

We sent an e-mail questionnaire to all lake association contacts provided by Maine CoLA. Among other questions, we asked, “What is the largest threat to the lakes of Maine?” After reviewing the approximately fifty responses, we found that the primary perceived threat to the health of the lakes is the lack of awareness of people who interact with the lake. Examples given by survey respondents were boaters unknowingly bringing invasive plant species into a lake region, people not realizing the need for buffer zones between their yards and the shores, and a lack of reporting violations of zoning laws.

Public-Private Partnerships

One way in which to maintain the water quality of the lakes in Maine is through the formation of public-private partnerships. Furthermore, although the enforcement power of MDEP is limited by a lack of available resources, the protection of lakes is enhanced by collaborations with local community associations who are able to work directly with residents (USEPA 2010).


The LakeSmart Program was started in 2002 by MDEP and works to promote the improvement of water quality in Maine by positively reinforcing the execution of best management practices. LakeSmart is working to shift the cultural norms of lake property owners so as to change popular practices of lakefront property landscaping.

MDEP is currently partnered with 26 lake associations in Maine to implement the program (MDEP 2008c). However, because of time and limited resources, the program is currently only implemented in areas where the associations can make a three year commitment to the program.

The LakeSmart evaluation process involves a site visit by a MDEP certified Soil and Water Conservation District employee who asks the property owners questions about the property and surveys the plot. The evaluator awards points based on the following five criteria: road and driveway, structures and septic system, lawns and footpaths, the shorefront, and any undeveloped land on the property.

Ideally, the program hopes to award 15% of shoreline properties with a LakeSmart certification. This number is based on the Social-Marketing Theory, which argues that 15% is the number needed to change community behaviors(MBLWQ 2005a, 2005b). However, one of the largest barriers to LakeSmart has been the cost. The price per year is about $48,800, making the cost per evaluation $529 (MDEP 2008c). As a result, from 2002 to 2008 only 140 properties were given a LakeSmart award.

Mousam Lake Restoration Project

The effectiveness of partnerships between the DEP and lake associations on lake health is evidenced by the Mousam Lake Restoration Project (USEPA 2010).

Mousam Lake, located in Acton and Shapleigh, is 863 acres in size and a popular destination for tourists and sport fishermen.  However, because of the development of over 700 homes along its shore, the water quality began to decline in the late 1970s as an increase in stormwater runoff sparked excess algal growth and changed water chemistry(Anderson 2008). In 1998, the lake was listed on MDEP’s 303(d) list for its inability to support aquatic life.

In response to a TMDL report conducted in 2003 that showed shoreline development as responsible for 51% of the excess phosphorous in the lake, 45 priority sites were identified and almost 80 homeowners were helped to implement best management practices. A 319 grant from MDEP was used to hold local workshops, such as septic socials where the importance of BMPs and the various ways to implement them were shared with the public. The project also established a Youth Conservation Corps that helped to install BMPs in 17 sites (MDEP 2004b).

In 2003, Mousam Lake was removed from the 303(d) list, and its water is now approximately three feet clearer than it was in 1992. Community involvement in the restoration process was key to the improvement of Mousam Lake. A significant portion of the funding for the projects ($400,000 out of $1.1 million) came from the local communities. Furthermore, without their participation in remediation efforts through the installation of BMPs, the success of the project would have been limited (MDEP 2004b).


Consequences of Lake Impairment

The system in which industry and residents benefit from lake use at the expense of lake health is not sustainable. Poor water quality impedes recreation, limits the use of lakes for drinking water, and decreases property values. Moreover, coupled lake and human interactions are characterized by a feedback loop, where the failure to protect one’s lake results in declining water quality, and in turn, decreasing economic value (Poor, Pessagno, and Paul 2007; Zhang and Boyle 2010; Michael, Boyle, and Bouchard 1996; Boyle et al. 1998; Boyle, Poor, and Taylor 1999).  One example is drinking water. Currently, 64% of drinking water comes from lakes, of which 58% is not filtered. If the water quality of a lake used for drinking water decreases, and no longer reaches national drinking water standards, the state will have to develop new water filtration facilities (Tolman 2010).  This will come at a large cost, thereby decreasing the value of Maine’s lakes.

Furthermore, several studies have illustrated the connection between lake water quality and property values, measured through hedonic pricing valuations (Michael, Boyle, and Bouchard 1996; Boyle et al. 1998; Boyle, Poor, and Taylor 1999; Poor, Pessagno, and Paul 2007).  Worsening water quality decreases property values within a watershed, regardless of whether they are waterfront (Poor, Pessagno, and Paul 2007).  In Maine, a one meter worsening of water quality, can reduce property values by 4 to 16% (Boyle et al. 1998; Michael, Boyle, and Bouchard 1996). Using the mean of this range, a one meter decrease in water clarity would cause a 10% decline in water front property value; if a house were worth $100,000 before the decline, it would be worth $90,000 after.  This would also mean that the municipality, given a 1.5% tax rate, would lose $150 on one property. When this is multiplied by 500 lakefront properties, the municipality loses $75,000.

In addition to water clarity, invasive aquatic plant species have also been shown to have detrimental economic impacts through decreasing property values (Perrings, Dalmazzone, and Williamson 2000; Zhang and Boyle 2010; Bouchard).  Consequently, the exponential growth rate of invasive species in Maine over the last 10 years is a noteworthy concern.  A recent study on IAPs in Vermont showed that IAP infestations can reduce property values by 1 to 16% per incremental increase (Zhang and Boyle 2010).  Considering that Maine’s localities depend largely on property tax revenue, decreasing water quality and increasing IAP infestations would have major economic effects at both the household and municipal levels (MDEPf 2005).

However, many of these studies find that the feedback system works in reverse; if stakeholders engage in positive conservation action, and water quality improves, the result will be increasing economic value.  Boyle and Bouchard (2003) report that lakes with greater water clarities have higher property values; a one meter improvement in clarity increases property values by 2.6 to 6.5%.  Moreover, if stakeholders engage in positive conservation behavior, and water quality improves, property values and tax revenue will also increase (Boyle et al. 1998; Boyle, Poor, and Taylor 1999).  Therefore, conservation efforts in lake water quality are vital for sustaining the economic value of lakes.  Though these estimations are subject to many limitations, they are effective in demonstrating the interaction between lake ecology, stakeholder behavior, and the economic value of lakes.  Studies such as these provide policymakers with a mechanism by which they can more appropriately weigh the costs and benefits of lake related policies. 


Alien Invasion: The Continued Spread of Invasive Aquatic Plants

If adequate prevention measures are not undertaken to stop the spread of IAPs, then many more of Maine’s lakes could become infested.  IAP infestations diminish water clarity and quality, leading to declines in lake-front property values and minimizing the recreational appeal of lakes (Williams and Hill 2009).  Infestations are also very expensive to control; each infested acre costs between $200 and $2,000 annually to manage by chemical or mechanical means (Bouchard).  Therefore, the further spread of IAPs would result in serious social, economic, and ecological costs.  Furthermore, once IAPs become a widespread issue in Maine, their transfer to un-infested water bodies would become even more difficult to prevent.  All of Maine’s major lakes could become infested if actions are not taken to stop IAP spread. 

Lakenomic Crisis: A Net Decrease in Lake-Related Expenditures

In the absence of enforced zoning laws and conservation efforts, residential and industrial development will continue to negatively impact the lakes of Maine.  Future increases in development, coupled with a lack of lake stewardship, will lead to an increase in the number of impaired lakes and thus a decline in lake water quality on the aggregate. The negative results of this will be threefold.  First, there will be a reduction in expenditures related to lake recreation. This would harm the businesses that support recreational activities, thereby crippling local economies.  Second, lakefront property values will decrease to the levels of non-lakefront property.  This would mean that lake-town municipalities will suffer from a loss in property tax revenue.  As their budgets shrank expenditures on public services would decrease, also harming the local communities.  Lastly, costly filtration facilities to process drinking water would need to be built to ensure that lake water meets the standards set by the Safe Drinking Water Act.

Cry me a Lake: Global Warming Increases Stormwater

The weather in Maine is becoming wetter, and this increase in stormwater means an increase of runoff into lakes (MVLMP 2009).  When looking at projected impacts of climate change on New England, it is hypothesized that by the year 2100 precipitation will have increased by 10 percent in the spring and summer and up to 60 percent in the winter (New England Aquarium 2010).  As more nutrients are washed into the lakes due to the increase in precipitation, the eutrophication process of lakes will be catalyzed.  Algal blooms will decrease the available oxygen in the water and many species of fish will be unable to survive.  The water would also become murkier and less conducive to swimming and other recreational activities.  Thus, property values on the degraded lakes would fall and local businesses reliant on tourism would collapse.  Because lakes are such a fundamental part of Maine’s economy, this would have widespread repercussions throughout the state.  Furthermore, it is important to note the growing need to implement BMPs along lake shorelines.  As a reactive measure, this scenario could lead to an increase in spending on the installation of lakefront properties, but given the smaller municipal budgets due to the loss in property tax revenue, it would come at an even greater cost to the society as a whole.

So Smart LakeSmart: A Wide-Spread Implementation of BMPs

Given the effectiveness of public involvement in restoring lake water quality, an increase in education initiatives in communities would have a positive impact on lake health.  If education measures are continued throughout the state and initiatives such as the Youth Conservation Corps of Mousam Lake are integrated into every community, the implementation of BMPs will become the norm as children educate their parents and community members educate one another on the importance of engaging in lake stewardship. 

In tandem with this, if LakeSmart extends to more lakes in Maine, a LakeSmart certification could become a widespread goal for lakefront homeowners in Maine.  Ideally, certified homes would sell for higher prices and every home on a lakeshore would actively work to implement BMPs.   One group especially important to involve in this scenario are the seasonal residents.  As it stands, in many lake communities the relationship between year-round and seasonal residents is strained due to financial disparities (Shannon 2010). However, working towards the common goal of lake protection through stewardship would improve these relationships. 


On average, Maine’s 5,785 lakes have remained mesotrophic, and their water quality is comparatively better than that of the US.  This, coupled with the fact that Maine has fewer infestations of IAPs than its neighboring states, has enabled the lakes to continue to be a vital natural resource for Maine’s economy and society.  Ecologically, lakes are an asset to the state as they provide unique habitats that support a diversity of aquatic life.  Economically, the total direct expenditures on lakes are equal to 5% of the state’s GDP.  Socially, the lakes of Maine support many local communities and their use has become of cultural importance (MRS Title 38 §436-A 1973). 

However, human activity threatens the health of Maine’s lakes.  Currently, 22,000 acres of lakes are impaired by agriculture and over twice that is impaired due to hydropower (MDEP 2010b).  Residential development also jeopardizes the health of Maine’s lakes as development has been shown to increase the amount of nutrients entering a lake by over 700% (Dudiak).  Industry and residents benefiting from lake use at the expense of lake health is not sustainable.

Public education has proven crucial to the preservation of Maine’s lakes.  Government initiatives to increase public awareness about the threats associated with IAPs has lead to a decrease in their spread in recent years.  Also, lake health can improve through public engagement in the implementation of BMPs.  In order to maintain the quality of Maine’s lakes, and in turn the services they provide, Maine’s population should prioritize their protection. The more residents and industries are aware of the consequences of lake degradation, the easier it will be to facilitate their protection.


Expand Prevention Measures for the Spread of IAPs

As a state with relatively few infestations, Maine has the fortunate opportunity to prevent its lakes from being overrun by IAPs as the lakes of neighboring states have been.  The prevention measures that have been undertaken by DEP should be expanded, and new measures should be developed and implemented.  Public education will be a key component of any plan to prevent the spread of IAPs. 

We recommend that more warning signs be installed at boat launches, along roadways, and at other key sites to inform the public of the threat of the spread of IAPs.  Increased signage identifying already infested water bodies will also be important.  The DEP has purchased some yellow buoys to mark areas infested by variable-leaf water milfoil, but they have not yet been implemented (MDEP 2008a).  These buoys could be very effective at reducing boat traffic in infested areas, minimizing disturbance to these areas, and thus decreasing the risk of propagation of milfoil through fragmentation.  Similar buoys could also be used in areas infested with other IAP species. 

Volunteer monitoring has been and will continue to be crucial to the prevention of the spread of IAPs.  Volunteer monitors have discovered most of the documented IAP infestations in Maine (Williams and Hill 2009).  More funds should be allocated by the DEP to finance programs such as the Maine Volunteer Lake Monitoring Program and the Courtesy Boat Inspection Program.  Early detection of infestations is crucial to preventing their spread. Therefore, we recommend that programs should also be developed to educate the general public on what IAPs look like, so that more lake-users know how to identify IAP infestations.

Overall, Maine has been proactive in attempting to halt the spread of IAPs, but more should be done.  More measures should be undertaken to increase public awareness of the issue.  Maine has an opportunity that many other states do not to prevent its lakes from becoming characterized by the presence of IAPs; this opportunity should not be passed over. 

Tax Incentive for Agricultural and Residential Best Management Practices

Given the negative effects of agriculture and residential development on lake health, it is necessary to engage both farmers and residents in positive lake conservation behavior.    Water quality conservation in agriculture requires reduced artificial fertilizer and pesticide use, careful manure management and storage, and riparian buffers (Bellows 2002). Currently, the National Resource Conservation Service of the USDA funds conservation initiatives related to agriculture that reduce erosion and NPS pollution (USDA 2010).  However, given that there are still over 23,000 lake acres impaired by agriculture, we recommend the state also fund similar projects to incentivize agriculturalists to engage in water quality protection.  This could be done through an income tax credit for farmers who voluntarily implement best management practices or a cost-share program that subsidizes BMPs by up to 75%, both of which have been initiated in Virginia (VDCR 2010).  The costs of these programs should be outweighed by the long-term economic benefits of good water quality

Additionally, given that a decline in water clarity may lead to a subsequent decrease in property values (Michael, Boyle, and Bouchard 1996; Boyle et al. 1998; Boyle, Poor, and Taylor 1999), it is in the interest of municipalities to take action to protect their lakes from pollution. In order to decrease the cost of lake stewardship for homeowners and businesses, we recommend a residential and commercial tax break for those who engage in best management practices. Although this will come as a short term cost for the municipality, in the long run it will improve water quality, and maintain property tax revenue.

Regular Valuation Studies

Currently, there is only one comprehensive valuation study that provides information on the value of lakes in Maine, and it is dated by 13 years.  Valuation studies are important because they attach a quantitative value to public goods that are not directly marketable.  This enables policymakers to more accurately weigh the costs and benefits of related policy.  Moreover, in the absence of information on lake value, policymakers may underestimate the benefits of initiating further policy to protect lakes.  Therefore, we suggest that MDEP initiate an annual or biannual valuation of lake use and related expenditures.  If lakes continue to significantly contribute to the state’s economy, the government should react by prioritizing funding towards protecting water quality by, for instance, increasing the enforcement of the Shoreline Zoning Act.

Increase Stringency of Existing Laws

The 2000 DEP survey of lakefront property owners found that although most respondents felt that their lake was in good health, the majority would like the existing laws to be more stringently enforced and strongly support education for community members on how to preserve the lake water quality (MDEP 2001).  The two laws we recommend strengthening are the Stormwater Management Law and Shoreland Zoning Law. 

The Stormwater Management Law currently requires that all new developments have natural buffers of vegetation between the water and the property.  However, we agree with the DEP in the need to expand the law so that it applies to old developments as well.  Since most of the lakefront homes in Maine were built before the 1960s, the amount of stormwater runoff would be decrease exponentially. 

Because of the home rule process inherent in the governance of municipalities in Maine, we see it necessary to increase education programs on lake stewardship in communities.  One way to do this would be through a change in the existing Shoreland Zoning Law.  The law should be expanded so as to provide municipalities with tiers of zoning regulations and standards so as to provide citizens with direct and informed road maps on how to best protect the lake given the specific needs of the municipality.  Currently, the law states that all areas within 250 feet of the high-water line of a great pond cannot serve as development sites, and that municipalities must issue zoning ordinances for development in other locations near a water body.  As suggested by the DEP, towns could be awarded as having gold, silver, or bronze standards.  We also feel that these laws should be uniform throughout watersheds.  In many cases, there are a number of towns that border a lake and thus comprise its watershed.  To maximize the level of stewardship, we feel that the most stringent zoning regulations chosen by one of the municipalities should be uniformly enforced throughout the lake shoreline, regardless of town boundaries. 

Coordinate Lake Association Efforts

Our group was given a list of lake association contacts from Maine CoLA, but after the majority of the e-mails that were sent were returned due to invalid addresses, it is clear that the list needs to be updated, and a few of the contacts responded saying they were no longer affiliated with the association.  On the Maine CoLA website, there is a portion where the lake associations in Maine can be found and contacted, but it has not been updated since 2005.  We feel that the lake associations, through Maine CoLA, should increase their collaboration.  Through the creation of an open forum where lake associations can discuss strategies for everything from funding to ways to connect with certain population demographics, their impact could be strengthened. 

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