Estimating future groundwater recharge rates over the Contiguous United States

Abstract:

Groundwater is an important source of potable water and is used for crop irrigation by millions of people in the United States, so it is vital to understand current and future rates of recharge to predict and manage groundwater availability. Understanding the spatial distribution of groundwater recharge at high resolution and how it is expected to change over time is especially important for water resource managers during this time of modern climate change. Predicting future recharge rates may help managers prepare for and mitigate the impacts of climate change on vulnerable populations that rely on groundwater.

This study estimates future groundwater recharge rates across the Contiguous U.S. at 800 m resolution using a water budget approach where quick flow and evapotranspiration are subtracted from effective precipitation. These three budget components were calculated for future climate change scenarios using previously-developed regression equations developed using historical datasets (Reitz et al., 2017), including atmospheric, geologic, and land cover data. Effective precipitation is estimated as the sum of precipitation and irrigation applied to crops and golf courses; the quick flow regression considers precipitation, hydraulic conductivity, and surficial geology type; and the evapotranspiration regression considers land cover, temperature, and precipitation.

Future groundwater recharge estimates were calculated for the Contiguous U.S. using predictions of future temperature and precipitation from down-scaled CMIP5 climate projections. Here we present these preliminary high spatial resolution predictions of future recharge to the year 2099, which 1) shows that both regional increases and decreases in recharge rates will occur across the Contiguous US, and 2) suggest long term trends in recharge that should be considered by water resource managers.

Reitz, M., Sanford, W. E., Senay, G. B., & Cazenas, J. (2017). Annual estimates of recharge, quick‐flow runoff, and evapotranspiration for the contiguous US using empirical regression equations. JAWRA 53(4), 961-983.