Drawdown of Lake Waukewan scheduled/ DES favors lower water levels

Following a lengthy study and two public meetings, the Dam Bureau of the New Hampshire Department of Environmental Services (DES) has scheduled a drawdown of Lake Waukewan.

Steve Doyon of the bureau said Friday that the level of the lake will be dropped to 540 feet immediately and, after 30-day period for public comment, another eight or nine inches in November. The drawdown, Doyon explained, was intended to provide sufficient storage capacity to mange the snow-melt and spring rains. Since March the water level has averaged 540.4 feet.

In recent years the level of the lake has become a source of mounting concern to both waterfront residents and state officials. After collecting information and data for a year, the bureau last month hosted meeting in Center Harbor and Meredith to sound residents about the management of water levels on Lake Winona and Lake Waukewan in anticipation of developing an operating plan for 2010 and ultimately a long-term plan.

Although there were some dissenters, most of the nearly 100 people who attended the meeting at the Meredith Community Center maintained that at 540 feet the lake level is too high, causing shoreline erosion and compromising water quality.

Jim Weber of the Dam Bureau said that because there are no gauges in the watershed, historical records of water levels are sketchy. However, records kept between 1926 and 1935, indicate that the average high water level was 539.8 feet, the average low water level 536.1 feet and the average water level 538 feet while the maximum high water reached 542.2 feet and the minimum low water 534.2 feet.

The Waukewan watershed, which is part of the greater Lake Winnipesaukee watershed, stretches over 13 square miles and consists of two lakes — Waukewan and Winona — joined by the Snake River and three ponds — Hawkins, Bear and Otter. Lake Winona covers 154 acres and Lake Waukewan 953 acres. Both lakes have a mean depth of about 22 feet. The shorelines of Lake Waukewan and Lake Winona measure 8.1 miles and 3.1 miles respectively and both are largely developed.

The dam at the Inn at Mill Falls has controlled water levels throughout the watershed since the early 19th century. Weber described the dam as "unique and complicated," explaining that water flows from an inlet at the southeast corner of Lake Waukewan into a canal lined by stone, then through a penstock to the surge tower before spilling into the flume and passing to the lake. The crest of the spillway was lowered 18 inches in 1975 when a hydro unit, along with a penstock and gate leading to it, were removed and another six inches in 1982 when the penstock was repaired. Weber said that the modifications to the dam ensured that its discharge capacity remained unchanged. "The discharge capacity is no different today than it was 100 years ago," he said. With all the flashboards removed, the water level will drop a half-an-inch a day.

Jody Connor, director of the limnology center at DES, is among those who insist that lake levels have been kept too high in recent years. He pointed out that because of the capacity of its outlet, it takes Lake Waukewan 18 months to flush, twice the median for New Hampshire's lakes and far less than Paugus Bay, for instance, which flushes a dozen times a year. Consequently, pollutants and nutrients linger longer and accumulate faster than in other lakes.

High water, Connor said, first defoliates trees and plants growing on the shoreline. Ultimately they decompose, drawing oxygen from the water and depositing nutrients in the sediment. Without the vegetation, high water hastens the erosion of the shoreline, which carries more nutrients and silt into the lake. At the same time, he said that the high surface water raises the groundwater level, compromising septic systems. When septic systems can no longer effectively treat phosphorus, it is carried to the lake by the groundwater. Connor stressed that as more phosphorus enters the lake, the more algae and cyanobacteria, which can be toxic to humans and animals, is generated and the more water clarity decreases.

The first cyanobacteria bloom was reported on Lake Waukewan in 2004 and blooms have occurred in each of the past three years. Connor said that there is no treatment for cyanobacteria since destroying the cells by boiling or chlorinating the water causes the toxins to be released. He said that the only way to reduce the likelihood of cyanobacteria blooms is to restrict the amount of phosphorus and nitrogen entering the lake.

"If the water level of the lake," Connor wrote in a memorandum last month, continues to remain at a point where it is negatively impacting properties, terrestrial plants and trees and shoreline, there will be a further degradation of water quality and continuation of cyanobacteria blooms."

Connor said that run-off has most likely increased as the extent of impervious surface within the watershed as expanded with development. At the same time, significant rain events in recent years have raised the lake level, which climbed to 541.8 feet after the heavy storm in August 2008. He emphasized that water quality required a management plan that would ensure sufficient storage capacity to address major rain events and maintain the lake at levels that prevented further erosion of the shoreline.

Meredith draws the supply for its public water system from the south end of Lake Waukewan, near where the town's treatment plant is located.