Impacts of winter lake drawdowns on downstream flows and stream ecosystems
September 2019 - June 2022
- Water Resources Institute Program
- Massachusetts Division of Fisheries and Wildlife
Winter lake drawdowns, whereby lakes are drawn down in fall and refilled in spring, are a common lake management tool in Massachusetts. Over the last 6 years, the MA Coop Unit has studied the impacts of drawdowns on lake littoral communities. Not only do winter lake drawdowns impact the hydrology of the lake, but they also cause unintended hydrologic alteration of downstream ecosystems. For example, in the fall during lake water level reductions, water releases cause higher flows than normal. In the spring during refill, flows are greatly reduced during a season when flows are normally the highest. There are general guidelines for drawdowns that include timing of drawdown, limiting maximum flows downstream during drawdown, and maintaining minimum flows downstream during refill; however, it is unknown the extent to which these guidelines are followed, and whether they protect downstream habitats and biota.
This project will build off preliminary work conducted by MassWildlife, the Massachusetts Division of Ecological Restoration (MDER), the Housatonic Valley Association, and the USGS MA Coop Unit downstream of Onota lake in Pittsfield, MA where we observed improved macroinvertebrate assemblages following restoration of flows in Peck’s Brook. MDER has identified priority sites for streamflow restoration downstream of winter drawdown lakes and conducted flow monitoring using time-lapse cameras in 2018. We will also use lake hydrology data from 18 drawdown and 3 non-drawdown lakes in Massachusetts to guide site selection. For this project, we will monitor hydrology, habitat, temperature, and biotic assemblages in streams to assess ecological responses to winter drawdowns.