The latest news about Maine lakes and ponds.

Local Environmental Organization Make Sure Lakes Stay Clean

August 29, 2007 - Naples -- As stiff winds stirred up choppy waves and rocked the dock, the participants leaned over the edge and placed yellow devices in the water.

They were learning to use depth readers, instruments that looked like flashlights on first glance but use sonar to measure the distance to the lake bottom. It was just part of a hands-on demonstration on Long Lake that provided a glimpse into the involved process of water quality testing.

Colin Holme and Bridey McGreevy of the Lake's Environmental Association, known as LEA, led the program last week. It was the third installment in a new summer education series that traces the journey of water from precipitation in the western foothills to the ocean.

In each part of the series, participants learn about environmental monitoring techniques used in various contexts.

LEA, based in Bridgton, collects water samples from 37 lakes and ponds and analyzes the results each winter. The information, which is passed on to the Maine Department of Environmental Protection and the US Environmental Protection Agency, can affect a body of water's eligibility for certain projects.

Testing of Long Lake involves a time-consuming process of gathering samples from three sites.

"This is by far the trickiest one to test, but we do get a whole lot of help," said Holme, the organization's field service director.

The process requires a lot more than just pulling water out of the lake. Special equipment is needed, as are specific procedures. Some equipment, for example, needs to be flushed with lake water three times so the results of sensitive tests, like those of phosphorus, will not be skewed.

The testing also involves a lot of logistical coordination. Luckily, the organization is assisted by people who give testers a ride to sites, lend their boats or allow access through their properties.

A Secchi disk -- a black and white circle connected to a tape measure-like device, is one way to evaluate water clarity. The disk is lowered into the water while a tester watches through a view scope, a big tube placed in the water. These kinds of measurements provide insight into the amounts of sendiment or algae, which thrive with nutrients like phosphorus and nitrogen.

Electronic probes measure dissolved oxygen and temperature at every meter of the water column.

In warm weather, layers form on the lake. The warm layer sits on top; under it is the thermocline -- where temperatures change rapidly with depth; and a stagnant cold layer lies at the bottom.

The combination of too much algae and not enough oxygen can kill cold water fisheries, like salmon and trout.

A long, clear core tube is used to pull samples from various depths. McGreevy, LEA's watershed education director, demonstrated how to trap water in the tube by plugging the open end with a thumb, the way a kid might play with a straw.

The samples are tested in a lab for qualities like pH, conductivity, color, chlorophyll content and phosphorus.

A grab sampler picks up phosphorus from lower depths. The device consists of a clear tube with blue stoppers held open by connections to a trigger mechanism. A weight sent down the line activates the trigger and closes the stoppers. Because of limited funds and the high costs of these tests, they are done only in August.

Although she is a board member who lives on Long Lake, the water quality testing demonstration was eye-opening for Jane Dann.

"I just can't imagine all this goes on!" she said.

This article originally appeared in the Portland Press Herald, August 23, 2007

Lakes: Long Lake
Regions: Sebago


Print this story

Email this story

return to Lake News