National framework for ranking lakes by potential for anthropogenic hydro-alteration

Lake hydrology faces multiple stressors from human activity. Land use (e.g., irrigated agriculture) and dams can alter lake inflows and outflows beyond natural ranges and changing climate conditions may exacerbate these disturbances. Broad-scale hydrologic disturbance measures are needed to assess human impacts on lake hydrology at regional and national extents. We developed a framework to rank lakes by the potential for anthropogenic alteration of lake hydrology (HydrAP) caused by dams and land use activities using national-scale datasets. We ranked lakes in the US EPA National Lakes Assessment (NLA) on a scale from zero to seven, spanning lakes with no apparent human hydrologic disturbances to lakes with large dams and/or intensive land use with potential to alter water levels. We inferred population HydrAP distributions in the conterminous US (CONUS) using the NLA probabilistic weights. About half of CONUS lakes were estimated to have moderate to high hydro-alteration potential (HydrAP ranks 3-7) and the other half had no to minimal hydro-alteration potential (HydrAP ranks 0-2). Water residence time (τ) and lake water-level change were associated with HydrAP ranks and support the framework’s ability to identify human infrastructure and activities that can alter lake hydrology. Lake τ were shorter in high HydrAP-ranked lakes. However, water-level change and HydrAP relationships varied by ecoregion and likely reflect different regional water management strategies that can promote or suppress large water-level fluctuations. The HydrAP framework is a robust tool to estimate human hydrologic disturbances and offers promise to support large-scale lake hydrologic assessments.

Impact/Purpose

National framework for ranking lakes by potential for anthropogenic hydro-alteration Both natural and constructed lakes and reservoirs provide valuable water-related ecosystem services such as drinking water, irrigation, cooling, flood control, recreation, and hydropower. Dams and landscape modifications such as ditches and canals facilitate and enhance these ecosystem services, but in turn can alter lake hydrology. These anthropogenic structures and activities can dampen or increase natural lake water-level fluctuations, impairing recreation, nearshore physical habitat, and water quality. Regional and national lake monitoring and assessment programs need to account for how these structures may alter lake hydrology. A clear system to integrate landscape metrics that indicate the potential for human hydrologic alteration would help to separate the geoclimatic and anthropogenic influences on lake level fluctuation. The authors developed a practical framework to rank lakes on a gradient of potential human hydrologic alteration (HydrAP) based on the presence of anthropogenic structures and activities that can alter lake hydrology: dams and land use. The premise of the HydrAP framework is that dam height and proportions of land use activities such as irrigated agriculture are indicators of the potential for human water management to alter lake water levels. The HydrAP framework uses readily accessible, national-scale geospatial information from NLA (US EPA), LakeCat (US EPA), and the National Inventory of Dams (US Army Corp of Engineers), so that lakes distributed across the conterminous US can be ranked using common data sources. The authors applied the HydrAP framework to lakes in the 2007 and 2012 NLA surveys to characterize the abundances and distributions of anthropogenic structures and activities with potential to affect water levels on CONUS lakes. The HydrAP framework is structured as a decision tree with modular components that can be adapted to different landscape contexts. This robust tool can support lake monitoring and assessment across the nation by providing critical insights on the relative influence of natural and anthropogenic influences on lake hydrologic condition and water quality and habitat attributes affected by lake level fluctuations.

Citation

Fergus, E., J. Renee Brooks, Phil Kaufmann, A. Pollard, A. Herlihy, Steve Paulsen, AND M. Weber. National framework for ranking lakes by potential for anthropogenic hydro-alteration. North American Lake Management Society Annual Meeting (NALMS 2020), Virtual meeting, OR - Oregon, November 16 - 20, 2020.