Agricultural Drought Assessment On The Key Growing Period Of Winter Wheat In Yongnian District,Handan City

With the warming of global climate,the climate of arid areas has changed significantly.Especially in recent years,due to the strong El Nino phenomenon,the middle and high latitudes in China have gradually become the new center of high temperature and drought.Yongnian District of Handan City is located in the south of North China Plain,which is an important grain producing area,but it has suffered from drought for a long time.Nowadays,the form of water use is increasingly severe,and the form of agricultural water supply is increasingly severe.Agricultural production is more vulnerable to drought,so it is necessary to turn agricultural drought resistance into agricultural drought prevention.Yongnian District of Handan city is a typical winter wheat growing area on the North China plain.Under the influence of multiple water conservancy engineering measures and strong human activities,the patchy and dynamic soil water changes with regional characteristics have been formed,which makes the prediction and early warning of regional agricultural drought more complicated and more realistic.Based on the analysis of regional soil water change,this paper constructed regional watershed hydrological model as a support,and finally realized the agricultural drought assessment in the key growing period of regional winter wheat.The main results are as follows:(1)The volume moisture content of soil in Yongnian region is spatially higher in the east and lower in the west.In the same period,the volume moisture content of the soil in the northern winter wheat growing area was lower than that in the southern.From the vertical variation analysis,the soil water content decreased faster at 0-20 cm,20-40 cm and 40-60 cm soil layers than at other soil layers.From the perspective of time change,the soil moisture content in each layer decreased with time after the winter wheat in Yongnian region entered the critical growth period,but there was an obvious increase of soil moisture content during the period.(2)The regional hydrologic model can describe the water cycle of farmland in detail,and obtain the simulated value of soil moisture in winter wheat.Through calibration verification,the final model area moisture data verifies that the average Nash efficiency coefficient is 0.88.(3)The analysis of rainfall in the yongnian region in the past 60 years shows that the precipitation in the low water years is mainly from June to September,and the precipitation in the growing period of winter wheat is less than 30% of the total annual precipitation.Through the simulation of a typical year,it was found that in a typical year of Drought,P=85%,P=90% and P=95%,the regional winter wheat experienced drought-non-drought-drought changes,among which P=90% and P=95% drought typical years occurred,and the central and eastern Yongnian region was prone to extreme drought in mid-April,which could be alleviated only in mid-May.(4)The analysis of agricultural drought evolution shows that the soil moisture condition,irrigation system and rainfall will affect the development of drought,and the soil moisture condition should be improved before the winter wheat enters the critical growing period in the dry year,and irrigation should be carried out timely according to the drought development in the early stage of drought development in mid-April.This study aimed at Yongnian district in handan area,with the characteristic of regional water resources in the parse area key growth period of winter wheat soil water on the basis of further explore the development situation of typical dry year rainfall drought,tries to analyze the whole different drought evolution law,can provide scientific basis for Yongnian district winter wheat drought control in the future.