Water footprints of irrigated crop production and meteorological driving factors at multiple temporal scales

Abstract

The water footprint (WF) of crop production indicates the water consumption for crop growth in a specific area over a certain time, enabling comprehensive water use efficiency assessments to be achieved for different types of water in an irrigation district. Daily and monthly blue (irrigation water) and green (rainfall) water resources are unevenly distributed in monsoon climate areas. However, the intra-annual evolution of the WF of crop production for a monsoon irrigation district is lacking. In the current study, maize and wheat production in the Baojixia Irrigation District (BID) of Shaanxi in China selected as the case study for the period 2008–2017, where the WF of crop production was analyzed based on a regional distributed hydrological model and the associated meteorological driving factors on daily, monthly, and yearly scales were identified. Results reveal that the method of WF of crop production established in the study can be applied to hydrological simulation of irrigated areas without drainage system. The blue WFs of maize and wheat production accounted for 34% and 36% of the irrigation water supplies, respectively. On a yearly scale, precipitation had the greatest impact on the green and blue WFs of maize, while sunshine hours and temperature had the greatest impact on those of wheat, respectively. On daily and monthly scales, different meteorological factors played key roles in the WF of crop production in different typical years. The time scale effect existed in the impact of meteorological driving factors on the WF of crop production, reaching its maximum on a monthly scale. Both water shortages and water waste coexist in BID. The irrigated area should rationally allocate blue water and effectively utilize green water resource to improve crop yield. Meanwhile, the time scale effect in the WF assessment of crop production and driving factors cannot be neglected. The irrigation strategy should be adjusted to cope with the impact of meteorological conditions according to the results and actual situation.