Natural and anthropogenic controls on lake water-level decline and evaporation-to-inflow ratio in the conterminous United States.
C Emi Fergus, J Renée Brooks, Philip R Kaufmann, Amina I Pollard, Richard Mitchell, G John Geldhof, Ryan A Hill, Steven G Paulsen, Paul Ringold, Marc Weber
Author Information
C Emi Fergus: Oak Ridge Institute for Science and Education, U.S. Environmental Protection Agency, Corvallis, OR. ORCID
J Renée Brooks: US EPA, Office of Research and Development, Center for Public Health and Environmental Assessment, Pacific Ecological Systems Division. ORCID
Philip R Kaufmann: US EPA, Office of Research and Development, Center for Public Health and Environmental Assessment, Pacific Ecological Systems Division. ORCID
Amina I Pollard: US EPA, Office of Water, Washington D.C. ORCID
Richard Mitchell: US EPA, Office of Water, Washington D.C.
G John Geldhof: Oregon State University, College of Public Health and Human Sciences, Corvallis, OR. ORCID
Ryan A Hill: US EPA, Office of Research and Development, Center for Public Health and Environmental Assessment, Pacific Ecological Systems Division. ORCID
Steven G Paulsen: US EPA, Office of Research and Development, Center for Public Health and Environmental Assessment, Pacific Ecological Systems Division. ORCID
Paul Ringold: US EPA, Office of Research and Development, Center for Public Health and Environmental Assessment, Pacific Ecological Systems Division. ORCID
Marc Weber: US EPA, Office of Research and Development, Center for Public Health and Environmental Assessment, Pacific Ecological Systems Division. ORCID
Lake water levels are integral to lake function, but hydrologic changes from land and water management may alter lake fluctuations beyond natural ranges. We constructed a conceptual model of multifaceted drivers of lake water-levels and evaporation-to-inflow ratio (Evap:Inflow). Using a structural equation modeling framework, we tested our model on 1) a national subset of lakes in the conterminous United States with minimal water management to describe natural drivers of lake hydrology and 2) five ecoregional subsets of lakes to explore regional variation in water management effects. Our model fit the national and ecoregional datasets and explained up to 47% of variation in Evap:Inflow, 38% of vertical water-level decline, and 79% of horizontal water-level decline (littoral exposure). For lakes with minimal water management, Evap:Inflow was related to lake depth ( = -0.31) and surface inflow ( = -0.44); vertical decline was related to annual climate (e.g., precipitation = -0.18) and water management ( = -0.21); and horizontal decline was largely related to vertical decline ( = 0.73) and lake morphometry (e.g., depth = -0.18). Anthropogenic effects varied by ecoregion and likely reflect differences in regional water management and climate. In the West, water management indicators were related to greater vertical decline ( = 0.38), whereas in the Midwest, these indicators were related to more stable and full lake levels ( = -0.22) even during drought conditions. National analyses show how human water use interacts with regional climate resulting in contrasting impacts to lake hydrologic variation in the US.
