Timely drought impact assessment for agriculture using a water–food systems approach

We present an integrated drought impact assessment framework to capture the cascading effects of drought on water supply, agriculture, and the broader economy, using California’s 2020–2022 drought as a case study. The assessment was conducted as the drought unfolded, applying a top-down methodology to estimate changes in agricultural water supply, cropland adaptation responses, and spillover effects across downstream sectors. Despite data limitations, we demonstrate a replicable framework for predicting land fallowing and estimating economic impacts, relevant for timely drought assessments in California and other semi-arid irrigated regions worldwide. The framework leverages diverse, readily available datasets, including remote sensing based evapotranspiration estimates, records of reservoir storage and allocations, crop insurance claims, and regional economic statistics, combined with economic modeling tools. Our results indicate that in both 2021 and 2022, surface water deliveries in the Central Valley declined by about 43%, with varying spatial footprints. To partially offset these reductions, groundwater pumping rose by 51% in 2021 and 41% in 2022, with the largest increases occurring in the Tulare Lake region. These shifts resulted in an estimated 212 thousand hectares (8.2% reduction) of fallowed land in 2021 and 282 thousand hectares (10.9% reduction) in 2022, with direct crop revenue losses of 1.2 and 1.5 billion dollars, and 8.9 and 10.2 thousand jobs lost. Regional value added declined by 1.3 billion in 2021 and 1.9 billion in 2022 from both crop production and downstream food processing industries. Ex-post validation using newly released state water balance and crop mapping datasets shows that aggregate fallowing and water supply impacts were captured within −13% to +2% at the Central Valley scale, with more variable performance across individual crops and hydrologic regions. We highlight both the strengths and limitations of the framework while demonstrating its usefulness for timely drought impact assessment and mitigation planning.