| Agriculture is one of the most sensitive industries to climate change.In the future climate change,the high proportion of agricultural water consumption severely restricts regional social and economic development and ecological security.Reducing agricultural water footprint is an important way to achieve regional sustainable development.In view of the shortcomings of agricultural water footprint research under climate change at home and abroad,guided by the water footprint theory,this paper takes the Shule River Basin in the arid region of northwest China as the research area,based on meteorological station data,CMIP5 global climate model simulation data and crops production data,etc.,using the CROPWAT8.0 model,calculated and analyzed the change characteristics of water demand per unit area and virtual water per unit quality of various crops in the Shule River Basin and counties(cities)from 1999 to 2014 and 2020-2050.Referring to the "Water Footprint Evaluation Manual",accounts the water footprint of agricultural production,agricultural consumption and per capita agricultural consumption from 1999 to 2014 in Shule River Basin,analyzes its changing characteristics,and clarifies the net output of agricultural virtual water in the Shule River Basin.Then,on the one hand,from the perspective of water footprint of agricultural production,the multi-objective optimization model was used to carry out an optimized simulation study of the water footprint of agricultural production after optimizing agricultural planting structure in Shule River Basin under the climate change of RCP2.6,RCP4.5 and RCP8.5 from2020 to 2050.On the other hand,From the perspective of the water footprint of agricultural consumption,referring to the "Guide to Healthy Diet for Chinese Residents(2018)",on the premise of ensuring human nutritional balance and health,the simulation was carried out,which of the water footprint of agricultural consumption and the per capita agricultural consumption in Shule River Basin afterthe dietary structure adjustment under the climate change scenarios of RCP from 2020 to 2050;Finally,accounts the net agricultural output of the Shule River Basin under the three climate change scenarios of RCP from 2020 to 2050,and analyzes the potential for the reduction of agricultural water footprint in the basin.The main conclusions are as follows:(1)The water demand per unit area of various crops in Shule River Basin and various counties(cities)showed obvious characteristics of periodic fluctuations from1999 to 2014,and the variation trend of virtual water per unit quality of various crops was obviously different.From 2020 to 2050,under the three climate change scenarios of RCP,the overall water demand per unit area of various crops is increasing,and the virtual water quantity per unit quality of various crops is generally decreasing fluctuantly.The multi-year average value of water demand per unit area and virtual water quantity per unit quality of various crops in 2020-2050 is generally higher than that of 1999-2014.(2)From 1999 to 2014,the water footprint of agricultural production in Dunhuang City,Guazhou County and Yumen City was much larger than that of Subei County and Aksai County,which is related to the type and area of crops planted in each region.The multi-year average per capita agricultural consumption water footprint of various counties(cities)in the Shule River Basin generally in order from Guazhou County,Yumen City,Aksai County,Subei County,Dunhuang City.and the water footprint per capita of agricultural consumption in Guazhou County,Yumen City and Aksai County exceeds the average of the basin.The multi-year average of water footprint of agricultural consumption of various counties(cities)in the Shule River Basin shows in order from Yumen City,Guazhou County,Dunhuang City,Subei County,Aksai County.The water footprint of agricultural production is much larger than the water footprint of agricultural consumption in Dunhuang City,Guazhou County,Yumen City and the whole Basin,the water footprint of agricultural production is slightly larger than the water footprint of agricultural consumption in Subei County,and the water footprint of agricultural consumption is 1.5332 million m3 larger than the water footprint of agricultural production in Aksai County,which indicates that the Shule River Basin is the net output area of agricultural virtual water,and the main output areas of agricultural virtual water are Dunhuang City,Guazhou County,and Yumen City.(3)Aimed to maximize agricultural economic returns and minimize the water footprint of agricultural production,optimization simulation of the planting structure of the Shule River Basin is carried out under the climate change scenarios of RCP2.6,RCP4.5 and RCP8.5 from 2020 to 2050.Taking the agricultural economic returns and the water footprint of agricultural production in 2014 as the baseline in the Shule River Basin,the agricultural economic returns after the optimization of the planting structure have been significantly improved(The multi-year average growth rate of agricultural economic benefits are 59.71%,61.20%,and 61.29%),and the water footprint of agricultural production after the optimization of the planting structure is significantly reduced(The multi-year average declines in agricultural production water footprint are 14.72%,13.36%,and 13.52%).In the optimized agricultural planting structure,economic crops are mainly vegetables,medicinal materials,spices,etc.,and food crops are mainly wheat.(4)With reference to the “Guide to Healthy Diet for Chinese Residents(2018)”,on the premise of ensuring human nutritional balance and health,the reasonable diet structure of the Shule River Basin is adjusted.The results of the water footprint of agricultural consumption after the dietary structure adjustment under the three climate change scenarios of RCP2.6,RCP4.5 and RCP8.5 in 2020-2050 are as follows: take the water footprint of agricultural consumption as the baseline in 2014 in county(city)of Shule River Basin,under the climate change scenarios of RCP from 2020 to 2050,the water footprint of agriculture consumption in Guazhou County is less than the baseline,the water footprint of agricultural consumption in Aksai County,Subei County and Yumen City is greater than the baseline,and the water footprint of agricultural consumption in Dunhuang City and the whole Shule River Basin will gradually change from larger than the baseline to being smaller than the baseline.(5)The net output of agricultural virtual water in the Shule River Basin showed a significant downward trend from 2020 to 2026,with a less change after 2026.Taking the net output of agricultural virtual water as the baseline in 2014 in the Shule River Basin,the multi-year average net output of agricultural virtual water declines are31.21%,29.86% and 30.10% under the climate change scenarios of RCP from 2020 to2050.On the premise of human nutrition balance and health,it's true that the optimization of planting structure can significantly reduce the net output of regional agricultural virtual water under the climate change scenarios of RCP from 2020 to2050.It's concluded that after optimizing the planting structure under the three climate change scenarios of RCP from 2020 to 2050 in Shule River Basin,the agricultural economic benefits are significantly greater than the baseline in 2014,and the water footprint of agricultural production are significantly less than the baseline in 2014.Taking human nutritional balance and health as a premise,the net output of agricultural virtual water after the optimization of planting structure and dietary structure is significantly less than the baseline in 2014.The optimization of planting structure is one of the important measures to reduce the agricultural water footprint of the Shule River Basin,which can provide a scientific basis for the rational use and regulation of agricultural water resources under the future climate change. |
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