A study by volunteers for a lake-monitoring program found nearly 65 percent of Maine’s lakes were clearer in 2010 than their historical averages.

The improved condition after two years of declining water clarity was the result of last year’s dry weather, according to Scott Williams, executive director of the Maine Volunteer Lake Monitoring Program.

Williams said the finding is the result of data gathered by several hundred certified lake monitors who took nearly 4,000 transparency readings on about 450 lakes throughout the state in 2010.

Water clarity is measured by lowering a small disk attached to a chain into the lake. Trained volunteers watch until it disappears. The depth at which the disk is no longer visible is considered the “Secchi depth,” and is taken as a measure of the transparency of the water.

He said last year’s findings contrasted significantly with those in 2008 and 2009, which were among the wettest years on record.

Williams said increased rainfall translates into increases in runoff, soil erosion and other pollutants that affect water clarity.

“We looked at lakes about the state and determined 64.9 percent of those lakes, in varying degrees, were clearer than their individual historical average,” Williams said.

“What’s interesting about that is, in 2009, it was very much in the other direction. A much smaller percentage, well under half, were clearer than their historical average.”

He said most people believe heavy rains and runoff flush and cleanse lakes and make them clearer.

But as shorelines and their watersheds become more developed, he said, runoff from melting snow and rain carries more pollutants, such as eroded soil particles and fertilizers. Lake water becomes cloudy with algae growth and silt.

Williams said the use of simple conservation practices like vegetated buffer strips to help filter pollutants from stormwater runoff can result in clearer, cleaner and healthier lakes.

“The other positive message that we see in this phenomenon is that lakes here in Maine appear to be resilient,” he said. “When we have a year like 2009 and have all that stormwater runoff, lakes seem to rebound to a degree fairly quickly in 2010.”

Founded in 1971, the Maine Volunteer Lake Monitoring Program is a statewide nonprofit conservation organization whose mission is to foster stewardship of Maine’s lakes and their watersheds.

The group accomplishes its mission by training and certifying volunteers in technical monitoring skills to collect lake data, and providing information concerning lakes to Maine people.

More than 850 individuals work in the group, including 600 volunteers who are certified to monitor water quality.

Williams said the group was founded 40 years ago, the same year the federal Clean Water Act was enacted.

“During the first part of its history, we were part of state government,” he said.

“But in the early 1990s, due to political changes and budget shortfalls, the decision was made to try and establish it as an entity outside state government … as a nonprofit organization,” he said.

“But we still work closely with the Department of Environmental Protection and have a diverse number of funding sources including state and federal governments and foundations and donations.”

For more information, visit www.mainevolunteerlake monitors.org.