PNNL

Abstract

Agricultural irrigation experienced rapid expansion, and its growing freshwater consumption is potentially exacerbating water scarcity issues. Previous studies predominantly relied on observations or land-only simulations, often neglecting land–atmosphere interactions or failing to capture the long-term evolution of irrigation practices at large scales. Here we analyse the effects of historical irrigation expansion on water fluxes and resources using seven Earth system models. Results show that irrigation expansion in many regions substantially decreases the net water influx from the atmosphere to land, further aggravating the existing drying trends caused by climate change. For example, irrigation expansion changed the trend of this net influx from -0.664(±0.283) to -1.461(±0.261) mm yr-2 in South Asia after 1960, from -0.209(±0.048) to -0.299(±0.031) mm yr-2 during 1901-2014 in Central North America. Consequently, regional terrestrial water storage depletion rate is substantially enlarged by irrigation expansion in some regions (e.g., -2.559(±0.094) to -16.008(±0.557), and -4.177(±0.059) to -11.000(±0.286) mm yr-1 in South Asia and the Mediterranean, respectively). Our results attribute the land water loss to irrigation expansion and climate change, calling for immediate solutions to tackle the negative trends.