Contents
Winter 2010 Home Page
General Notices
President's Message
Lakeside Notes
Littorally Speaking
Welcome Aboard New Monitors
National Lakes Assessment
Algal Toxins
Thank You Supporters!
Customize Your Monitoring Packet
Passings
The EPA has published the draft findings of the first-ever baseline study of the nation’s lakes. The National Lakes Assessment (NLA) provides estimates of the condition of both natural and man-made lakes, ponds and reservoirs greater than 10 acres in surface area and at least one meter deep. The draft study rated 56% of the lakes in the United States as good, and the remainder as fair or poor. This study marks the first time that EPA and its partners have used a nationally consistent approach to survey the ecological water quality of lakes. A total of 1,028 lakes were selected at random for the study, which took place during the summer of 2007. Ten Maine lakes were included in the study, as the map below shows.
A wide range of indicators of lake health were assessed in the study, including water quality (nutrients, dissolved oxygen and algal density); biological indicators (algae and zooplankton); recreational indicators (pathogens and toxins from algae), and physical habitat (lakeshore and shallow water habitat cover). Peter Silva, Assistant Administrator for EPA’s Office of Water, indicated that the NLA is a first step in evaluating how successful efforts have been to protect and restore the quality of lakes throughout the country. Silva also stated that future surveys of this type will help to advance our understanding of important regional and national patterns in lake water quality.
Findings and Implications for the Nation’s Lakes
While it is certainly good news that 56% of the lakes in the U.S. are in relatively good condition, the fact that the remaining 44% are in fair or poor condition is a dramatic and troubling finding. Why are so many of our lakes in trouble?
Degraded lakeshore habitat, which was rated “poor” in 36% of the lakes in the study, was the most significant of the problems that were assessed. The removal of critical buffer vegetation, including trees and shrubs along shoreline and riparian areas, and the construction of docks, marinas, homes and other structures along lake shores contributed to the findings. The study concluded that: “Poor biological health is three times more likely in lakes with poor shoreline habitat.”
The second biggest problem for U.S. lakes is high nutrient levels, with about 20% of the lakes in the study having high levels of phosphorus and nitrogen. Lakes with excess nutrients are two and a half times more likely to have poor biological health, and are likely to experience algae blooms, excess weed growth, reduced water clarity and other problems, such as adverse impacts on a wide range of aquatic life, drinking water and recreation.
The NLA also looked at how lakes that were impacted by wastewater in the 1970’s (particularly direct discharges to lakes, which are now virtually nonexistent) were affected by treatment systems and other pollution control activities. It found that 75% of that group of lakes had either improved, or showed no change since that time, suggesting that investments in systems to treat wastewater discharges to lakes since that time appear to be working, even as lakes and their watersheds have become more populated.
The survey findings suggest that our lakes are vulnerable to excess human disturbances, and it supports reports from state lake management programs throughout the country which increasingly report that development pressures on lakes are steadily growing.
The survey also suggests that degraded shoreline habitat causes significant stress to lake systems, which in turn makes the case for a need for stronger management of lakeshore development. The NLA looked at lakes and their shorelines, including the effects of shoreline development on lakeshore habitat. It did not directly assess the effect of watershed development, which also has a strong influence on the health of lake ecosystems. However, it is reasonable to assume that the water quality findings of the survey reflect conditions in lake watersheds, as well.
The conclusions reached in the National Lakes Assessment do not come as a great surprise! In fact, they vindicate efforts used in Maine for four decades by the Maine DEP and VLMP volunteers to monitor, assess and protect the State’s lakes and ponds.
It is important to note that the NLA survey describes the target group of lakes that were sampled, and makes general conclusions about the nation’s lakes. Information for this article was extracted from EPA summaries of the NLA survey, and from an overview of the study prepared by EPA Scientist, Neil Kamman.
The draft NLA study is available online at:
Maine Volunteer Lake Monitoring Program
vlmp@mainevlmp.org
24 Maple Hill Road, Auburn, ME 04210
(207) 783-7733
www.MaineVolunteerLakeMonitors.org
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