Sectoral contributions to surface water stress in the coterminous United States

Abstract

Here, we assess current stress in the freshwater system based on the best available data in order to understand possible risks and vulnerabilities to regional water resources and the sectors dependent on freshwater. We present watershed-scale measures of surface water supply stress for the coterminous United States (US) using the water supply stress index (WaSSI) model which considers regional trends in both water supply and demand. A snapshot of contemporary annual water demand is compared against different water supply regimes, including current average supplies, current extreme-year supplies, and projected future average surface water flows under a changing climate. In addition, we investigate the contributions of different water demand sectors to current water stress. On average, water supplies are stressed, meaning that demands for water outstrip natural supplies in over 9% of the 2103 watersheds examined. These watersheds rely on reservoir storage, conveyance systems, and groundwater to meet current water demands. Overall, agriculture is the major demand-side driver of water stress in the US, whereas municipal stress is isolated to southern California. Water stress introduced by cooling water demands for power plants is punctuated across the US, indicating that a single power plant has the potential to stress water supplies at the watershed scale. On the supply side, watersheds in the western US are particularly sensitive to low flow events and projected long-term shifts in flow driven by climate change. The WaSSI results imply that not only are water resources in the southwest in particular at risk, but that there are also potential vulnerabilities to specific sectors, even in the 'water-rich' southeast.

Nonstationarity of low flows and their timing in the eastern United States

“…The region is one of the wettest parts of the US, receiving 700-1600 mm of precipitation per year. However, due to population growth and associated increased use of surface and groundwater resources, the future is expected to bring water stress for this area (Averyt et al, 2013). Some of these changes are already being observed.…”

Projecting water yield and ecosystem productivity across the United States by linking an ecohydrological model to WRF dynamically downscaled climate data

“…The WaSSI model simulates the full monthly water (ET, Q, and soil moisture storage) and carbon balances (GPP, ecosystem respiration, and net ecosystem productivity) for each land cover class at the given watershed scale. This model has been tested in a variety of geographical regions, and widely used for quantitatively assessing combined or individual effects of climate change, land use/cover change (LUCC), and population dynamics on water supply stress and ecosystem productivity (i.e., carbon dynamic) over the CONUS (Sun et al, , 2011aLockaby et al, 2011;Caldwell et al, 2012;Averyt et al, 2013;Tavernia et al, 2013;Marion et al, 2014;Sun et al, 2015a, b). The model has also been applied internationally in Mexico, China (Liu et al, 2013b), and Africa (McNulty et al, 2016).…”

Future Water Budgets and Water Supply Stress under Climate Change and Urbanization in the Upper Neuse River Basin, North Carolina, USA

“…The WaSSI model has been used to assess the combined or separate effects of climate change, land cover change and anthropogenic water use on historic and future water supply stress and ecosystem productivity over the US, Mexico, China and several African countries (Lockaby et al, 2011;Averyt et al, 2013;Tavernia et al, 2013;Liu et al, 2013;McNulty et al, 2015). For this study, the focus is on the combined impacts of urbanization and climate change on annual and long term water yield.…”