Risk Prevention Of Agricultural Drought Based On Regional Water Balance

Drought refers to a kind of meteorological disaster which is harmful to human's production and life caused by severe or abnormal drought.The process of drought is slow and easy to be neglected,but the losses caused by drought can not be underestimated,among which agriculture is the industry most vulnerable to the direct impact of drought.Agricultural drought is a disaster caused by the failure of crops to grow normally due to the lack of soil moisture,resulting in a large area of yield reduction or failure.It is the result of the combined action of natural factors,social factors and ecological factors,which seriously restricts the development of agricultural economy in Hebei province.The direct consequence of agricultural drought will result in crop yield reduction and food shortage,while the long-term drought will lead to land resource degradation and ecological environment deterioration,and ultimately restrict the normal production and life of human beings and the sustainable development of social economy.Agricultural drought can be improved through the comprehensive development and utilization of multi-source water resources,the reducting of irrigation quota,the improvement of irrigation water utilization coefficient,and the optimization of crop planting structure.Selecting the crops with higher water suitability under the natural precipitation conditions and optimizing planting structure can improve the utilization rate of natural precipitation,reduce the agricultural water consumption and maintain a virtuous cycle of agricultural ecosystem,also can prevent and mitigate the impact of drought on human life,which has great practical significance to society.The agricultural production database of 17 counties in xingtai city was established based on the statistical yearbook data from 1994 to 2015 and the precipitation data from 1981 to2015;The theoretical water demand of total yield of winter wheat,summer corn and cotton was estimated under the condition of actual sown area and yield per unit area.According to the division natural precipitation data from 1966 to 2015 in annual precipitation type,selecting the low water year(2001),the low water year(2005),the high water year(2009),the high water year(2013),the flat water year(2015),using the temperature vegetation index model to interpret the drought situation of crops with large water deficit in the growth period and to determine the spatial distribution of the drought situation;the water ecological suitability of 9 main crops in Xingtai City under natural precipitation is evaluated and the most suitable crops under natural precipitation are determined,under the policy of prohibition and restriction of underground water exploitation,the agricultural layout of Xingtai City is adjusted according to the principle of"social-economic-ecological"co-development.The results show that:1)During the growth period of winter wheat,corn and cotton in Xingtai City,the winter wheat has the largest water shortage under both yield and total production conditions,and corn and cotton are water balance under natural precipitation conditions in most years,but real annual precipitation unevenly,a few years,water shortage water deficit is smaller.From the perspective of space,the water deficit of winter wheat in xingtai county in the western mountainous area during the growth period is 0.49×10~8 m~3 compared with that of natural precipitation;the winter wheat planting area of ningjin county and longyao county in the central piedmont plain belt is large,and the water deficit during the growth period is 1.5×10~8m~3 compared with the natural precipitation;the water deficit of winter wheat in weixian and linxi counties in the eastern plain area is relatively larger,the water deficit during the growth period is 0.69×10~8 m~3 compared with the natural precipitation.2)There was a relationship between winter wheat drought and precipitation year type,and the winter wheat drought was more serious in drought year than in high water year and normal water year.The space shows a relatively high level of drought in the western mountainous area and the eastern plain area,and a relatively low level of actual drought in the central piedmont plain because of the relatively rich shallow groundwater resources and low surface temperature.3)According to the index of water ecological adaptability,the water suitability of nine crops in Xingtai City is evaluated under different precipitation years.The order of water-suitability of crops in high-water years is as follows:sorghum>millet>soybean,maize>peanut>cotton>sweet potato>rape>sunflower;the order of crop water-suitability is as follows:sorghum,soybean>corn>millet>cotton>peanut>sweet potato>rape>wheat>sunflower;the order of water-suitability of crops in the year of plain water is sorghum>soybean>corn>millet>peanut>cotton>sweet potato>rape>sunflower;the order of water-suitability of crops in low water years is sorghum>soybean,maize>millet>cotton>peanut,sweet potato>rape>sunflower;the order of water-suitability of crops in dry years is sorghum>soybean>maize>millet>peanut>sweet potato>cotton>rape>sunflower.Generally speaking,sorghum,soybean,maize,millet,cotton,peanut and sweet potato have better water adaptability.4)Formulate the planting structure adjustment plan of xingtai county under the constraints of irrigation water,grain and oil security and sown area.The simulation results showed that the sown area of winter wheat in the city should be reduced by 25826 hm~2,and the sown area of winter wheat in ningjin county,longyao county and weixian county with large water shortage should be significantly reduced.The sown area of corn should be increased by 31094 hm~2,but the sown area of corn in nanhe county and ren county where water resources are relatively abundant should be reduced by 917 hm~2 on average.The soybean seeding area of the whole city should increase by 11194 hm~2,and the soybean seeding area should significantly increased in the counties of weixian and guangzong which are short of water resources.The planting area of sweet potatoes in the western mountainous area and the eastern plain area should be increased by a large amount,with a total increase of11684hm2 in the whole city.Cotton needs to reduce its planting area in weixian and nangong counties where water resources are relatively scarce.The planting area of groundnut in western mountainous area should be increased.The design scheme ensures the grain yield and economic benefits of each county,and can save 9.15×10~8 m~3 water resources in the city.In areas with large water shortage,such as longyao county and ningjin county,the water can be saved,and the simulated planting structure optimization effect is obvious.5)Considering the spatial water shortage,the optimization scheme of planting structure and the actual soil conditions,the spatial optimization scheme of planting structure design in Xingtai City is obtained.(1)The western mountainous areas should follow the existing policies,return farmland to forestry,vigorously develop forestry,develop ecotourism and other projects,and form a characteristic agricultural system.The sandy soil resources in neiqiu,xingtai and shahe counties with large water shortage are abundant.On the basis of reducing the sowing area of winter wheat,the sowing area of sweet potato,peanut and other rhizome crops should be appropriately enlarged.(2)The central piedmont plain belt is located in the overexploited area of shallow groundwater.The existing water resources should be reasonably utilized.Sandy loam and loam resources are abundant in the west of Ningjin and Longyao counties where water shortage is relatively large,reduce the sowing area of winter wheat,expand the sowing area of cotton,peanut and sweet potato,and realize the efficient utilization of water resources.(3)The eastern plain area is located in the prohibiting area of deep groundwater,this area groundwater resources are scarce,and in the south where water shortage is nangong,weixian and linxi counties need to reduce the sowing area of winter wheat,sow crops with good soil adaptability and water adaptability such as corn and soybean instead of winter wheat.The rest counties can expand the planting area of sweet potato,peanut and cotton in sandy areas such as qinghe county and weixian county,and expand crops with high water adaptability such as corn and soybean in areas where clay loam is suitable.Improve utilization rate of natural precipitation,promote the development of agriculture of use natural precipitation.