The impact of cropland spatial shift on irrigation water use in China

As the utmost component of water utilization, irrigation water use (IWU) has raised extensive concerns of academics who devoted to achieve regional water security. IWU per unit area of cropland varies across regions due to changing natural physical factors; thus, cropland spatial location change would drive regional total IWU variation even if the total area of cropland remains unchanged. Here, based on CROPWAT model and multi-source data, we estimated the IWU change caused by cropland spatial shift in China. Results show that cropland centroid in China moved to the northwest by approximately 56 km during 1990–2015, leading to national IWU increase by about 18 billion m3 (7.3%). By region, IWU in the northwest enhanced the greatest with nearly 23 billion m3, which was mainly caused by the high IWU per unit area of cropland (759–810 mm) which was more than five times as the national average. Furthermore, irrigation water productivity in the northwest (0.66 kg/m3) was relatively low, which was only 15% of the national average. Therefore, for alleviating water-grain contradiction, emphasis should be placed on raising yield and declining IWU per unit area on existing croplands rather than reclaiming new cropland in the northwest, which requires advanced production and irrigation technologies to be prioritized for the northwest. This research could provide valuable references for policymaking in order to achieve regional sustainable land-water management.