Citation:

Fergus, C., Reneej Brooks, Phil Kaufmann, Steve Paulsen, A. Pollard, AND M. Weber. PATTERNS OF LAKE HYDROLOGIC CHARACTERISTICS RELATED TO WATER LEVEL DRAWDOWN ACROSS THE CONTERMINOUS U.S. Association of Sciences of Limnology and Oceanography, Victoria, BC, CANADA, June 10 - 15, 2018.

Impact/Purpose:

Communities benefit from the ecosystem services provided by the Nation’s lakes and reservoirs, particularly the hydrologic capacity to buffer against the impacts of flooding and drought. However, changes to lake water levels can adversely affect a lake’s physical habitat, water quality, and plant and animal communities. Disturbances such as land use conversion, water extraction, and changing climate may significantly alter lake water-level regimes and impact lake condition and delivery of ecosystem services. However, lake hydrologic condition across the nation is poorly understood. Using the USEPA National Lake Assessment (NLA), we describe how hydrologic characteristics vary across lake types (natural vs. reservoirs) and across regional settings. The patterns we found suggest that water management activities and not climate alone are important drivers of lake water levels, especially in western regions. Identifying the regional patterns of lake and reservoir drawdown and evaporation can help inform management strategies to identify hydrologically vulnerable systems in the face of changing climate and water use demands. In addition, it helps provide the lake and landscape context to better understand the drivers of lake hydrologic condition across the nation.

Description:

Lake hydrologic characteristics related to water levels, such as drawdown distance and evaporative water loss, affect the physical, chemical, and biological condition of lakes. Disturbances such as water withdrawal and changing climate may alter water-level regimes and impact lake integrity. Predicting how systems may respond to altered climate and increased demands on water resources should improve if we understand how hydrologic characteristics vary across lake types (natural vs. reservoirs) and ecoregions. We describe lake and reservoir hydrologic characteristics across the conterminous U.S. using data collected in 2007 and 2012 from >1000 lakes during the US EPA’s National Lakes Assessment. Measured lake hydrologic variables include vertical and horizontal drawdown distances, and water stable isotope values that were used to derive evaporative water loss and water residence time. Reservoirs and natural lakes differed in their hydrologic patterns across ecoregions, with reservoirs generally being more drawn down, whereas natural lakes were more evaporated. Reservoirs in western regions had high drawdown distances and natural lakes in the plains had high evaporation. These patterns suggest that water management activities and not climate alone are important drivers of lake water levels, especially in western regions. Residence time was greater in natural lakes compared to reservoirs. Examining these patterns can inform management strategies to identify hydrologically vulnerable systems in the face of changing climate and water use demands.

Record Details: