Temporal And Spatial Relationship Between Virtual Water And Available Water Resources Of Main Crops In Northwest China

The shortage of water resources seriously restricts the healthy development of agriculture in arid and semi-arid areas.With the continuous growth of China’s population and the rapid expansion of cities,the development potential of cultivated land resources in the southeast is becoming more and more limited.The center of gravity of the main production areas of crops such as grain,melons and fruits is moving northward.The role of the northwest in ensuring food security is becoming more and more prominent.However,the water and soil resources in this area do not match.Under the current imbalance of large-scale production of crops and insufficient water resources,high water consumption agricultural production will bring great challenges to the water resources security in Northwest China.Therefore,the key to the sustainable development of agriculture in Northwest China is to clarify the impact of largescale crop production and trade on water resources in Northwest China,and to seek the basic ways to alleviate the pressure of agricultural water use.Based on water footprint and virtual water theory,combined with penman Monteith model,CROPWAT 8.0 and ArcGIS software,this paper calculates the production water footprint of 1 1 types of crops in 63 cities(prefectures and leagues)in Northwest China,systematically analyzes the temporal and spatial evolution characteristics of crop production water footprint,explores the law of crop virtual water flow,and evaluates the impact of crop production and trade process on water resource pressure.The following results were obtained:(1)The growth and development of most crops in Northwest China depend on irrigation water,and only the type of apple water consumption is mainly rainfall.There is less rainfall in Northwest China from March to may in spring,and the water consumption of crops is mainly irrigation water;From June to August in summer,it is rainy season,and the proportion of green water footprint of crops increases significantly;In autumn and winter,due to the reduction of the growth consumption of some crops,the blue-green water footprint gradually decreases.The spatial distribution of the green water footprint of crop yield per unit area is consistent with the regional rainfall,increasing from northwest to Southeast.On the contrary,the blue water footprint shows a spatial distribution pattern of high in Northwest and low in southeast,which is consistent with the distribution of large-scale irrigation areas.(2)From 2000 to 2019,the water footprint per unit yield of crops in Northwest China decreased by 38.8%,but the reduction rate of water footprint per unit yield of crops was less than the rate of output growth,and the water demand of crops increased by 40.7%.By 2019,the water consumption for crop production has reached 135.326 billion m3,and the growing demand for crop water consumption is not conducive to the sustainable development of regional agriculture and water resources.From the perspective of spatial distribution,due to different regional crop production structures,the total water footprint of crop production in cities(prefectures and leagues)in Northwest China varies.Due to the large scale of crop production,high water consumption areas are mainly distributed in Hulunbuir,Tongliao,Kashgar and Aksu.(3)In the past 20 years,the number of crop virtual water export areas in Northwest China has increased from 26 to 37,and the export areas have gradually gathered to the north.It has basically formed a virtual water output center represented by Hulunbuir City,Kashgar region and Hotan region and a virtual water input center led by provincial capitals in the southeast.The output center mainly exports corn and cotton,and the input center mainly imports rice.The provincial capital city alleviates the pressure of local water resources by importing crops,so as to use water resources for other industries with more functions of the provincial capital city.(4)Northwest China is short of water resources,and the available water for agriculture is further reduced.The water resources in some areas are under serious pressure due to the largescale production of crops.Xi’an City,as a representative of the high water resource shortage concentration area,has limited water resources.The local water resource shortage can be alleviated by expanding the import and trade volume of crops.The high water self-sufficiency concentration area represented by Changji Hui Autonomous Prefecture is less dependent on the outside,but the agricultural water pressure is increasing due to the continuous growth of crop output.The available water resources in Northwest China are unevenly distributed,and the agricultural production structure is not reasonable.In order to realize the healthy development of agriculture and the sustainable utilization of water resources,it is necessary to reasonably adjust the local water resources allocation,appropriately reduce the production of high water consumption products,effectively control the water footprint of crop production,and reduce the water pressure.From the perspective of water footprint and virtual water,this study evaluated the risk of agricultural water resources security on the basis of quantifying the water footprint and virtual water of crop production in Northwest China.In order to optimize crop production structure,coordinate the utilization of agricultural water resources and alleviate the pressure of agricultural water use in Northwest China Provide theoretical support.