Impacts of climate extremes on agricultural water scarcity under historical and future periods and the spatial scale effect

BackgroundBoth blue water and green water contribute to agricultural water scarcity, which is subjected to impacts of escalating climate extremes, e.g., precipitation and temperature extremes. However, an explicit quantification of the possible effects of compound climate extremes on agricultural water scarcity index (AWSI) under historical and future climate is absent and current research often overlooks how different spatial scales influence agricultural water scarcity.MethodsWe applied an integrated AWSI, which incorporates blue water and green water, to estimate agricultural water scarcity in provincial and basin scales in China, and to determine the association of AWSI with compound climate extremes over the historical period 1971–2010 and for future period 2031–2070.ConclusionsOur results indicate a marked escalation in AWSI during dry years and periods of elevated temperatures, and precipitation significantly impacts AWSI more than temperature variations. In secondary basins, AWSI was about 25.7% higher than the long-term average during dry years, increasing to nearly 49% in exceptionally dry conditions. Comparatively, in tertiary basins, the increases were 27.7% and 55%, respectively. In years characterized by high temperatures, AWSI rose by approximately 6.8% (7.3% for tertiary basins) from the average, surging to around 19.1% (15.5% for tertiary basins) during extremely hot periods. Future climate change would further intensify AWSI and amplify the effects of climate extremes, particularly in Inner Mongolia with changes of AWSI over 200%. Southwestern China could also experience expanding agricultural water scarcity under future climate scenarios. Improving irrigation efficiency has potential to alleviate water scarcity by up to 30%. Moreover, it illustrates that AWSI assessment at the tertiary basin level could better capture the influence of climate extremes on AWSI compared to assessments at the secondary basin level. As a whole, the investigation offers an in-depth evaluation of the influence of compound precipitation and temperature extremes and research scale on water scarcity.