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USGS Explores Climate Change Threats to Popular Lake Maintenance Practice
U.S. Geological Survey (USGS) researchers are investigating whether winter lake drawdowns, a widespread low-cost lake management technique, may become less effective as the climate changes. Allison Roy, Unit Leader, USGS, Massachusetts Cooperative Fish and Wildlife Research Unit, and a team of researchers at the University of Massachusetts Amherst are using satellite mapping and hydrologic modeling to provide insights into the future of the practice in the Northeast and Midwest U.S. This work is funded by the USGS Northeast Climate Adaptation Science Center.
“I've been in the Coop Unit for almost 12 years, and winter lake drawdown was the very first topic the state fish and wildlife agencies wanted addressed,” Roy says. “They didn't know much about who was doing it, when, how often, and what the impacts are – they felt underprepared to make management recommendations.”
“Drawing down” a lake is like opening the drain of a bathtub, allowing water to flow into neighboring streams to expose a few feet of shoreline. Lake managers and homeowners across the Northeast and Midwest U.S. often partially drain their lakes in the winter to kill plants that accumulate along shorelines, prevent ice damage to docks and other infrastructure, and provide flood storage. Many see drawdowns as greener alternatives to chemical invasive species control.
Yet as the climate warms, there is a real concern that there will eventually not be enough winter ice to kill aquatic weeds, or enough rain or snowfall to refill the lakes the following spring.
The team is using remote sensing data to identify lakes being drawn down across the Northeast and Midwest, particularly lakes that don’t have state permits and thus aren’t in existing databases. From there, they are modeling potential future ice cover on the lakes given different climate change scenarios, allowing managers to understand which areas may eventually be too warm to ice out invasive plants. They are also projecting how long it could take for the lakes to refill after drawdowns, helping managers decide how much (or little) water to drain.
Based on these data, Massachusetts has updated its state winter drawdown guidelines, with suggested limits on how much water lake owners release and when they start refilling to ensure lakes are able to refill to healthy levels by the following spring.
“This is about as rewarding as science gets,” Roy says. “We’ve worked closely with the folks at the Massachusetts Department of Environmental Protection and the Division of Fisheries and Wildlife and give them the information they need to make important changes.”
Roy’s ongoing climate modeling complements her previous work looking at the environmental impacts of winter lake drawdowns on lake and stream ecosystems. Through a series of projects by former Ph.D. student Jason Carmignani, the team assessed the extent and ecological impacts of winter drawdowns in Massachusetts, funded by the Massachusetts Division of Fisheries and Wildlife. They found that the practice can harm shoreline species like mussels and insects, and that it disrupts physical habitats. It also creates seasonally unnatural stream flows – open dams create high water levels in the normally dry fall, while closing the dams to recharge lakes creates low water levels when streams have high flows due to spring snowmelt.
“There are still so many questions,” Roy says.
Next, her team will explore using satellite imagery to measure algal blooms in drawn-down lakes and model how climate change could affect future water quality in these bodies of water.
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