Regional Differentiation Of Water Consumption For Grain Crop Production And Responses To Changing Environment In China

Agriculture has always been a major water user in China,accounting for 61.6% of the country’s total water withdrawal.Wheat,corn,rice and soybean account for more than90% of the water consumed for grain crops production nationwide.The high spatial heterogeneity of natural resource endowments and the still uneven socioeconomic development levels among regions have led to significant spatial differences in water use efficiency for grain production within China.Previous studies on water consumption for food production in responses to the future changes have ignored the intranational disparity in economic and social development levels,so that the relevant results and recommendations are difficult to be concretely implemented in agricultural water resources management at the prefecture level.In the face of the increasingly intense intersectoral competition for water and the uncertainty of water shortage crisis under climate changes,quantitative analysis of regional differences in water consumption in grain production and associated responses to the changing environment at the prefecture level is a key basis for implementing the strictest water resource management and maximizing agricultural water use efficiency.In this study,four major grain crops,wheat,maize,rice and soybean,were selected as research objects,and 357 prefectures in mainland China were used as spatial units to construct a dynamic identification index system and method for grain production water consumption hotspot regions based on crop water footprint accounting;the spatial and temporal evolution characteristics of hotspot regions in terms of each subject function in water consumption of grain production from 2004 to 2018 were clarified;the responses of regional differentiation of grain crop water consumption hotspots to future climateeconomic-social change scenarios were analyzed;the evolution of grain crop related water consumption and virtual water flow patterns in typical hotspot regions were analyzed.The main results are as follows:(1)The dynamic identification index system and method of water-consuming hotspot areas of food production were constructed.By selecting four typical representative elements at the dimension of agricultural production,natural resources,economic level and social development,a system of indicators for identifying waterconsuming hotspot areas in food production based on crop water footprint accounting was constructed;the number of hotspot area types was determined by the maximum silhouette coefficient method,taking into account the historical long-term formed human-land relationship and stability of the regional system;the K-means cluster analysis method was applied by calculating the classification center of the baseline year.The dynamic identification method of water-consuming hotspot areas of grain production was developed.(2)The regional differentiation characteristics of water consumption in grain production and the functional spatial and temporal evolution characteristics of hotspot regions in China from 2004 to 2018 were clarified.Based on the established index system and method for dynamic identification of hotspot areas,the historical evolution process and differentiation characteristics of each index at the four dimensions of agricultural production,natural resources,economic level and social development were considered comprehensively.Eight types of hotspot areas for water consumed in grain production were identified at prefectural level.The results show that during 2004-2018,1/3 of the prefectures in China belonged to extremely high and high water-consuming area types for grain production,where the total water consumption for grain production accounted for2/3 of the national total,mainly in the Northeast and Yellow-Huai-Hai Plain regions.(3)The regional differentiated response characteristics of water consumption for grain production in China under future changing environment were elucidated.Based on the shared socioeconomic paths(SSPs)-representative concentration paths(RCPs)scenario framework,the future spatial and temporal evolution of each index at the four dimensions of agricultural production,natural resources,economic level,and social development,as well as the response characteristics of regional differentiation in China’s grain production,were analyzed.The results show that water consumption for grain production in China will likely continue to increase in the future,and the largest increase will occur under the SSP5-RCP8.5 scenario,with most of the prefectures remaining spatially stable in terms of hotspot region types;nearly one-fifth of the prefectures will still undergo functional transformation,with nearly half of them changing from lowwater-consuming regions under the SSP2-RCP4.5 and SSP5-RCP8.5 scenarios to high or very high water-consuming regions(2080s).(4)The evolution of water consumption and multi-scale virtual water flow patterns for grain production in typical hotspot areas was analyzed.Taking Shandong province,a typical high-water-consuming region for grain production,as an example,the water consumption of grain production,as well as grain related international,interprovincial,and inter-prefectural virtual water flow patterns under the changing environment were further analyzed.The results show that the annual average water footprint of grain production in Shandong province was 40.44 billion m3/a;in 2018 as a net grain virtual water importer,the international,inter-provincial and inter-prefectural grain virtual water flows was 13.77 billion m3/a,31.1 billion m3/a and 0.76 billion m3/a,respectively.Under future climate-economic-social changes,the trends of water consumption changes in grain production vary among scenarios,with water consumption for grain production decreasing by 3.0% by 2050 s under SSP1-RCP2.6,and increasing by 1.4% and 3.5%under SSP2-RCP4.5 and SSP5-RCP8.5 scenarios,respectively;the virtual water export of grain will be on an increasing trend.The regional agricultural water saving potential can be effectively enhanced by adjusting the diet structure on the consumption side.In conclusion,this study constructs a dynamic identification index system and method for hotspots in terms of water consumption for food crop production,and applies it at the prefectural level in mainland China to clarify the spatial and temporal evolution and associated responses under the past and future changing environment,further analyzes the evolution of water consumption and virtual water flow patterns in grain crop production in typical hotspot regions,and initially proposes corresponding regulation strategies.The analysis are intended to provide scientific basis and methodological references for improving water conservation and efficiency in agriculture and coping with global changes.