An annual drawdown of 3ft is utilized at Onota Lake to protect against flooding during spring runoff, protect against shoreline destruction from ice, and to provide limited control of invasive species. The current ability to drawdown the lake is limited by the size of the existing outflow pipe. During reconstruction of the Onota Lake dam in 1995, the 4 foot diameter outlet pipe previously in place was replaced with a 2 foot diameter pipe. This, inevitably, reduced the maximum outlet flow to twenty five percent (25%) of the previous capacity. With the current outlet pipe it has been difficult to achieve drawdown within the ideal timeframe and climate. There are concerns regarding flooding, p
roperty damage and increased shoreline erosion due to limited drawdown capacity and time required to drawdown the lake.
In addition, drawdown is a potentially effective means of controlling nuisance aquatic species within shallow areas of Onota Lake. Since nuisance plants such as E. watermilfoil, and Curlyleaf Pondweed are most problematic in shallower areas, this management technique may be particularly effective for the control of nuisance plants. An annual drawdown of 4 ft would be expected to reduce milfoil and curlyleaf pondweed cover over 257 acres of the lake. Additionally, a drawdown of 8ft would be expected to increase the aquatic plant management area to over 324 acres of total coverage area. (Wagner, 1996) The LOPA Drawdown Committee reviewed lake bathymetry and existing data in 2003. The committee estimated that an annual drawdown of 6ft would approximately double the aquatic plant management area and recommended periodic deep drawdowns. The City of Pittsfield has received a grant from the Department of Environmental Protection under their Nonpoint Source Pollution Grant Program to improve the infrastructure of the dam to achieve more effective drawdowns. This is just one component of the grant, which includes the development of this website.