DOI: 10.5061/dryad.cc2fqz65x
title: Sustainable use of groundwater may dramatically reduce irrigated production of maize, soybean, and wheat

description: Groundwater extraction in the United States (US) is unsustainable, making
 it essential to understand the impacts of limited water use on irrigated
 agriculture. Here, we integrate a gridded crop model with satellite
 observations, recharge estimates, and water survey data to assess the
 effects of sustainable groundwater withdrawals on US irrigated
 agricultural production.  Our model agrees with
 satellite-based estimates of evapotranspiration (R2 =
 0.68), as well as survey production estimates from the United States
 Department of Agriculture (R2 = 0.82 – 0.94 for county-level
 production and 0.37 – 0.54 for county-level yield). Using the optimistic
 assumption that groundwater extraction equals estimated effective aquifer
 recharge rate, we find that sustainable groundwater use decreases US
 irrigated production of maize, soybean, and winter wheat by 20%, 6%, and
 25%, respectively. Using a more conservative assumption of groundwater
 availability, US irrigated production of maize, soybean, and winter wheat
 decreases by 45%, 37%, and 36%, respectively. The wide range of simulated
 losses is driven by considerable uncertainty in surface water and
 groundwater interactions, as well as accounting for adaptation and the
 many aspects of sustainability, including environmental flows. These
 results demonstrate the vulnerability of US irrigated agriculture to
 unsustainable groundwater pumping, highlighting the difficulty of
 expanding or even maintaining irrigated food production in the face of
 climate change, population growth, and shifting dietary
 demands. Our findings are based on reducing pumping by fallowing
 irrigated farmland, so alternate pumping reduction strategies or
 technological advances in crop genetics and irrigation technologies could
 produce different results.
description: The archived data consists of 9 raster files, all of them
 in Network Common Data Form (NCDF). All files represent the continental
 United States at a 5 arc minute resolution. The first
 three files contain the calibrated SLPF parameter for pDSSAT. They have
 two dimensions, i.e. latitude and longitude, and one variable, SLPF. The
 first three characters of the file name indicate the name of the crop
 simulated, namely mai for maize, soy for soybean, and wwh for winter
 wheat. The last five characters of the file names are
 "_slpf". The other six files contain the
 pDSSAT model output. These files have  have 3 dimensions and 5 variables.
 The dimensions of the files are latitude, longitude, and time. The
 dimension time has 5 levels, one for each growing season simulated. The
 following variables are stored in these files:  total evapotranspiration
 between planting and harvest (mm; ETCP), yield (kg [dm]/ha; HWAM), season
 irrigation (mm; IRCM), physiological maturity date (YrDoy; MDAT), and
 planting date (YrDoy; PDAT). Same as the parameter files described above,
 the first three characters of the character file names indicate the name
 of the crop simulated. The last two characters indicate if the simulation
 is irrigated (Ir) or rainfed (Rf).