Spatio-temporal variation of irrigation water requirements for wheat and maize in the Yellow River Basin, China, 1974-2017

Irrigation is a prerequisite for the sustainable development of agricultural production. With the existing of water resources shortage and climate change, it is of great importance to explore the variation of crop irrigation water requirement (IWR) in the Yellow River Basin (YRB). Based on 1974-2017 meteorological dataset from 96 stations, we analyzed the spatio-temporal variation characteristics of meteorological factors and crop IWR during the growing seasons of four main crops including spring wheat, winter wheat, spring maize and summer maize, respectively. Furthermore, we explored the dominant meteorological factors of the crop IWR variation. The results indicated that daily mean temperature (T) had a significant upward trend, while the effective precipitation (P-eff) did not change significantly during the growing season of each crop in the past 44 years. Crop IWR had increasing trend with 9.9 mm/decade, 4.3 mm/decade, 6.4 mm/decade for spring wheat, winter wheat, spring maize respectively, while a slight decreasing trend with -1.7 mm/decade for summer maize. It is noted that extremely significant increase in crop IWR were mostly located in Ningxia, southern Gansu and eastern Qinghai. Moreover, P-eff, net radiation (R-n) and relative humidity (RH) were identified as the dominant meteo-rological factors influencing variations of IWR for all crops. In the context of significant increase in T and un-certain future precipitation patterns, IWR for spring wheat, winter wheat and spring maize in the YRB has shown an upward trend which is not favorable to the sustainable development of water resources. It is urgent to take effective water-saving measures to hedge the adverse impact of climate change on agriculture. These findings can provide scientific basis for rational allocation of agricultural water resources in the YRB.