You are here:
WHAT FACTORS INCREASE THE RISK OF SEVERE LAKE WATER-LEVEL DRAWDOWN IN THE U.S.
Citation:
Fergus, C. Emi, J. Renee Brooks, Phil Kaufmann, R. Hill, A. Herlihy, A. Pollard, M. Weber, AND Steve Paulsen. WHAT FACTORS INCREASE THE RISK OF SEVERE LAKE WATER-LEVEL DRAWDOWN IN THE U.S. ASLO 2019 Aquatic Sciences Meeting, San Juan, Puerto Rico, February 23 - March 02, 2019.
Impact/Purpose:
Natural lakes and constructed reservoirs provide important ecosystem services that include water sources for human activities (e.g., drinking water, recreation), habitat for wildlife, and buffers against adverse effects of drought and flooding. Disturbances such as land use intensification, water extraction and diversion, and changing climate may significantly alter lake water-level regimes and lead to declining water levels. However, across the United States lake hydrologic condition and its major drivers are poorly understood. We combined U.S. EPA National Lakes Assessment survey data with geospatial data in LakeCat (USEPA) to examine drivers of lake water-level drawdown. We modeled and predicted the probability of lake drawdown severity class using hypothesized lake morphology, watershed, and climate variables for natural and man-made lakes distributed across the conterminous U.S. Our study identifies lake characteristics and landscape and climate contexts that are associated with large water level declines in U.S. lakes. This information can help inform management strategies to identify water bodies that are particularly vulnerable to changing water use demands and climate.
Description:
The severity of lake water-level drawdown negatively impacts the physical, chemical, and biological condition of lakes. EPA’s National Lakes Assessment (NLA) determines lake drawdown severity of sampled lakes, but it is not well understood what landscape and climate variables are associated with severe drawdown at regional to continental extents. We combined NLA data on >2,000 lakes distributed across the conterminous U.S. with geospatial data in LakeCat (USEPA) to examine drivers of lake water-level drawdown severity based on least-disturbed reference lakes within the respective ecoregions. We modeled the probability of lake drawdown severity class for natural and man-made lakes using random forest models based on hypothesized lake, watershed, and climate variables. We found that drawdown severity was related to watershed hydrology and climate attributes, but these relationships were not always consistent between lake types. As expected, drought-like conditions were associated with a greater probability of severe water-level drawdown in both natural and man-made lakes. However, high percentages of groundwater contribution minimized drawdown severity in natural lakes, but increased risk in high elevation man-made lakes, which may be related to water management activities in those landscape contexts. Identifying how environmental and climate variables influence drawdown severity can inform management and improve risk predictions under changing landscape and climate conditions.