Analysis On Temporal And Spatial Pattern Of Irrigation Water Demand Of Main Crops In China

Water resources are the basis for human survival and an important prerequisite for realizing the sustainable development of ecological environment.As a large agricultural production country,with the development of social economy and the increase of population,the shortage of water resources is becoming more and more serious,which has become the main factor restricting agricultural development in China.Therefore,it is of great practical significance to study the irrigation water demand of main crops,analyze its temporal and spatial pattern for realizing the long-term goal of agricultural sustainable development in China.Based on the meteorological data and rainfall data of 824 meteorological stations from 1978 to 2015,this paper selects the main crops in China,combining with the penman Monteith formula recommended by the Food and Agriculture Organization of the United Nations(FAO)and the single crop coefficient method,the crop water demand under the condition of no water stress is calculated.The effective rainfall during the crop growth period is calculated by using the SCS-CN model.It can confirm the irrigation water demand of crops and analyze its temporal and spatial pattern.In addition,in order to evaluate the water resources security of rainfed and irrigated agriculture in China,in this paper,the total crop water demand,effective rainfall,irrigation water demand and the best planting area in each province under the two conditions were calculated,so as to provide scientific basis and reference for the rational,efficient and optimal distribution of water resources in China.The main conclusions showed that:(1)From 1978 to 2015,the annual average value of rice irrigation water demand in China was between 3～551mm.The overall trend of its spatial change was that it gradually decreased from north to south,and the spatial distribution of multi-year average effective rainfall during rice growth period was uneven;The irrigation water demand of wheat in China decreased from West to East,and the effective rainfall increased from West to East,which was opposite to the spatial change trend of irrigation water demand;The spatial distribution of maize irrigation water demand in China generally shows a trend of high in the northwest and low in the southeast,which is reflected in the larger northern region,the second in the central region and the smallest in the south.(2)Under the condition of rain fed agriculture,the total water demand in China is about 585×10~9m~3,with total effective rainfall of 365×10~9m~3,with a total irrigation water demand of 220×10~9m~3。On the premise of knowing the demand for agricultural water resources and effective rainfall,this paper studies the rationality of the current planting area from the perspective of water resources security,and calculates the best planting area.The best planting area in China is 1184×10~9m~2,accounting for 88%of the original planting area.Therefore,under the planting structure in 2015,more irrigation water is needed to ensure food production.