Natural and anthropogenic controls on lake water‐level decline and evaporation‐to‐inflow ratio in the conterminous United States

Abstract

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 fits 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 (β = À0.31) and surface inflow (β = À0.44); vertical decline was related to annual climate (e.g., precipitation β = À0.18) and water management (β = À0.21); and horizontal decline was largely related to vertical decline (β = 0.73) and lake morphometry (e.g., depth β = À0.18). 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 (β = 0.38), whereas in the Midwest, these indicators were related to more stable and full lake levels (β = À0.22) 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 United States.

Reservoir Drawdown Highlights the Emergent Effects of Water Level Change on Reservoir Physics, Chemistry, and Biology

“…Water levels in many lakes and reservoirs are changing due to altered climate and water management practices (Kraemer et al., 2020; Wada et al., 2014; Ye et al., 2017). While global climate change is driving a general trend of decreasing water levels in lakes and reservoirs (Fergus et al., 2022; Yao et al., 2023), local human activities also cause water level changes over multiple timescales (e.g., Furey et al., 2004; Hannoun & Tietjen, 2023; Liu et al., 2019; Rimmer et al., 2011). In particular, many human‐made reservoirs experience large water level fluctuations on daily to annual timescales due to management for flood control, hydropower, fish passage, irrigation, and drinking water provision (Fergus et al., 2022; Hamilton et al., 2022; Jiang et al., 2018; Keller et al., 2021; Wada et al., 2014).…”

“…While global climate change is driving a general trend of decreasing water levels in lakes and reservoirs (Fergus et al., 2022; Yao et al., 2023), local human activities also cause water level changes over multiple timescales (e.g., Furey et al., 2004; Hannoun & Tietjen, 2023; Liu et al., 2019; Rimmer et al., 2011). In particular, many human‐made reservoirs experience large water level fluctuations on daily to annual timescales due to management for flood control, hydropower, fish passage, irrigation, and drinking water provision (Fergus et al., 2022; Hamilton et al., 2022; Jiang et al., 2018; Keller et al., 2021; Wada et al., 2014). The seasonal variability of water level in managed reservoirs is, on average, more than four times greater than in natural waterbodies (Cooley et al., 2021), and extreme, non‐seasonal water level fluctuations may also be more common in these managed systems.…”

Diverse response of shallow lake water levels to decadal weather patterns in a heterogeneous glacial Boreal Plains landscape

“…The timing and amplitude of lake water level fluctuations (WLFs) affect the physical, chemical, and biological processes that are integral to lake structure, function, and ecosystem services (Bayley & Prather, 2003; Fergus et al, 2022). Lakes occur abundantly in belts across mid‐latitudes and the boreal, largely associated with recent glacial activity (Hutchinson, 1957).…”

“…The hydro‐geoclimatic setting varies tremendously across these latitudes, which also coincide with regions experiencing greater non‐stationary climatic forcings (Stralberg et al, 2020; Tetzlaff et al, 2013). Natural spatiotemporal patterns in lake hydrology and WLF, and thus lake function, vary among lake types and hydro‐geoclimatic settings, and are influenced by multiple anthropogenic factors (Fergus et al, 2022; Kraemer et al, 2020). Lake hydrology studies that capture regional differences in climate, geology, and topography across spatial and temporal scales are needed for developing conceptual frameworks (Buttle, 2006; Devito, Creed, & Fraser, 2005; Devito, Creed, Gan, et al, 2005; Fergus et al, 2021; Winter, 2001) to improve our understanding and prediction of natural ranges in lake hydrology and WLF and disentangle the relative influence of land‐use and climate change on ecosystem function.…”

Disentangling natural and anthropogenic effects on benthic macroinvertebrate assemblages in western US streams

“…Structural equation modeling (SEM) offers an analytic framework to evaluate hypothesized networks of interrelated variables (Grace et al, 2010) and has been applied to address complex questions pertaining to coupled natural and anthropogenic systems (e.g., Fergus et al, 2022; Meißner et al, 2019; Palt et al, 2022; Schmidt et al, 2018; Tang et al, 2020). Unlike conventional statistical analyses like multiple regression, SEM offers greater application and flexibility to model complex systems by mathematically representing multivariate networks of response and predictor variables.…”