Response of irrigation water supply to demand in China and its effects on yields

Irrigation is the most significant human water withdrawal globally, playing a pivotal role in ensuring food security. However, the lack of detail irrigation datasets across spatial and temporal dimensions limits our comprehensive understanding of how historical irrigation water supply has responded to demand fluctuations and, consequently, its effect on agricultural yields. In this study, we employed a combination of remote sensing products, meteorological data, and various statistical datasets to estimate gridded monthly irrigation water demand and supply in China at a spatial resolution of 0.1° during the period 2000-2019. The results indicate that the national annual irrigation water demand is 122.23 km³, with rice accounting for the highest share (39.25%), followed by wheat (36%) and maize (24.75%). While the annual irrigation water supply is measured at 317.42 km³, with rice (62%) dominating, trailed by maize (21.13%), and wheat (16.87%) contributing the least. The mismatch in the distribution of irrigation water supply and demand among crops underscores variations in irrigation systems and the availability of water sources for irrigation. Notably, in the downstream of the Yellow River Basin and the Huaihe River Basin, the irrigation water supply falls short of demand when not accounting for irrigation efficiency, primarily attributed to a scarcity of water during the wheat growing season in spring (Mar. to May), indicating a potential water stress on wheat yield in this region. This study enhances our understanding of the intricate relationship between irrigation water supply and demand in China, offering valuable insights to support regional water resources management and allocation strategies.