Crop irrigation water requirements mismatch the actual water allocation in the anthropogenic-regulated Yellow River Basin

Abstract

Study area: The Yellow River Basin (YRB) in China is a critical grain-producing region that experiences severe water scarcity and intense competition for water resources. Study focus: Agricultural irrigation is the primary water use in the YRB. However, the spatiotemporal patterns and alignment between irrigation water requirement (IWR) and supply remain unclear. This study quantified the spatiotemporal variations in IWR in the YRB, focusing on the alignment within the irrigation system. A process-based crop water model was used to calculate IWR for five major crops from 2001 to 2100, with future projections under three Shared Socio-economic Pathways. The spatiotemporal patterns of total IWR and whether they align with actual irrigation water use and supply were analyzed. New hydrological insights for the region: IWR in the highest irrigation areas exceeded 500 mm/yr. Two annual peaks were identified: March to May and July to August. Spatial and seasonal mismatches in the irrigation system were evident. Spatially, irrigation water use exceeded requirements in the source regions and upper reaches but failed to meet requirements in the middle and lower reaches. Seasonally, irrigation water supply peaked earlier than crop water requirements. Future projections suggest that seasonal mismatches will persist and may intensify due to delayed requirement peaks and increasing requirements. These findings highlight the importance of institutional adaptation in enhancing water resilience and sustainability in the Anthropocene.