| Uneven spatial and temporal distribution of water resources and low per capita availability are the main factors limiting agricultural development in China.The transportation of grain from the north to the south has intensified the pressure on water resources in the main agricultural regions in the north,and it is important to quantify agricultural water consumption in time to guide agricultural development.The agricultural water footprint can reflect the amount of water consumed in agriculture and is one of the most important indicators to measure the water used in the production and consumption of regional agricultural products.Reducing the agricultural water footprint is conducive to alleviating the regional water resources pressure,and adjusting the agricultural planting structure is an effective way to reduce the agricultural water footprint.Located in a semi-arid region,Dingxi City is one of the main agricultural production areas in Gansu Province and is currently facing the prominent problem of large water demand for agricultural development and insufficient water supply,and water shortage has been one of the decisive factors limiting the sustainable development of agriculture in the region.Therefore,how to optimize the agricultural planting structure in Dingxi City to achieve the dual objectives of improving agricultural economic efficiency and reducing agricultural water footprint,to alleviate the pressure on regional water resources,has become an urgent problem to be addressed in the region.This paper focuses on the study area of Dingxi City to quantitatively reveal the current situation of agricultural water footprint and simulate the optimization of agricultural planting structure in the region.The specific topics of the study include three aspects:(1)using CROPWAT8.0 model software to calculate and analyze the change characteristics of water demand per unit area and virtual water per unit mass of10 crops in the study area during 2009-2019;(2)studying the current situation of agricultural water footprint and analyzing the virtual water flow characteristics in Dingxi city from the perspective of production and consumption;(3)design a simulation scenario and establish a multi-objective optimization model to simulate and optimize the agricultural planting structure of Dingxi City.The main conclusions are as follows.(1)The total multi-year average produced water footprint of Dingxi City is26.67×108m~3,and there are spatial differences in the total produced water footprint of each county(district).The differences in the production water footprint of different types of crops are related to the planting structure,and the total multi-year average production water footprint of potatoes,corn,and herbs is the largest,accounting for more than 70%of the city’s production water footprint.The structure can change the regional agricultural production water footprint.At the same time,the multi-year average blue water footprint of the six counties(districts),except Min County,accounts for more than 40%of the produced water footprint,indicating that agricultural production in Dingxi City relies on irrigation water to a higher extent.(2)The total multi-year average consumption water footprint of agricultural products in Dingxi City is 10.4×108 m~3,and the per capita annual consumption water footprint is 370.9 m~3.The total consumption water footprint of counties(districts)is positively correlated with the total resident population,and the per capita consumption water footprint is negatively correlated with the urbanization rate,and increasing the urbanization rate can reduce the per capita consumption water footprint of agricultural products.(3)Dingxi City is a net virtual water output area,and there are certain problems in the agricultural planting structure.the average annual net output of virtual water in2015-2019 pieces is 16.08×108m~3,and all seven counties(districts)show a net virtual water output.There is a spatial mismatch in virtual water output,specifically in the northern water-scarce Anding and Tongwei areas with the largest net output,and in the southern relatively abundant precipitation Zhangxian and Minxian areas with small net output.There are differences in the virtual water flow of different types of crops,with potatoes,corn,herbs,and vegetables showing a net output and wheat,the main ratio,showing a net input,which indicates that the region is not completely self-sufficient in agricultural products.(4)Optimizing planting structure is an important way to improve agricultural economic returns and reduce the production water footprint.The results of the six simulation scenarios show that when the agricultural economic benefits are unchanged,optimizing the planting structure can reduce the regional agricultural water footprint by27%～40%;when the total agricultural production water footprint is unchanged,optimizing the planting structure can increase the regional agricultural economic benefits by 1.89～2.27 times.When the amount of available water resources in the region remains unchanged,the higher the degree of self-sufficiency of agricultural products,the lower the economic benefits per unit of water resources;when the degree of self-sufficiency of agricultural products is the same,the greater the amount of available water resources in the region,the greater the growth of agricultural economic benefits.According to the simulation results of the representative solution selected according to the target of the 14th Five-Year Plan of Dingxi City,the adjusted planting structure can reduce the water footprint of agricultural production by 1.05×108m~3 and the net virtual water output by 2.95×108m~3 when meeting the 72%growth of economic benefits,therefore,the development of medicinal herb industry in Dingxi City can better achieve the goal of improving agricultural economic benefits and reducing the water footprint of production,and alleviate the regional water resource pressure.In addition,an appropriate increase in the planting area of staple wheat is conducive to increasing the degree of food self-sufficiency in the region. |
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