Study On Rainfall Effective Utilization Coefficient Of Typical Plots In Shijin Irrigated Area Based On HYDRUS-1D

Shijin irrigation area is a typical large-scale irrigated area in north China.The main crops planted in the irrigated area are winter wheat and summer corn,and the irrigation mode is the combination of well and canal.In recent years,with the continuous decline of the lower water level in the irrigated areas,the water ecological environment in the irrigated areas deteriorates,and the tension of water resources intensifies.How to make full use of water resources and improve the efficiency of farmland water use is of great significance to the sustainable development of Shijin irrigation area.This study considering the soil texture,the root layer thickness,vadose vertical layered soil and crop type,etc.,using soil water movement theory,based on the typical HYDRUS-1D building block field soil moisture migration model,USES the typical plots of quantity system observation of soil moisture content of soil hydraulic characteristic parameters of the model calibration and verification,on this basis,according to the Hebei irrigation quota standards set 258 kind of situation,to simulate the process of field soil moisture migration and in combination with different rainfall and irrigation,with the aid of HYDRUS-1D model and the calculation equation of effective rainfall,The distribution law of rainfall effective utilization coefficient of typical block in Shijin irrigation area is obtained,which provides reference for the follow-up study of rational and efficient utilization of water resources and effective rainfall in Shijin irrigation area.The main research results are as follows:(1)Calibration and verification of soil hydraulic characteristics parameters of the HYDRUS-1D model were carried out.For two typical plot within 200 cm soil is reduced to 6 layer,using the growth period of winter wheat field measured soil moisture content in 2019 the rate of model parameter,using corn field measured soil moisture content in the summer of 2019 parameters are verified,among them,the average error between 0.04 to 0.03,the average absolute error range of 0.01-0.03,root mean square error between 0.01 to 0.05.The results show that the Hydr US-1D model can simulate the soil water transport in a typical block.(2)Based on the HYRRUS-1D model,the soil moisture in a typical block during the observation period was simulated.During the simulation period,the evapotranspiration of trees in winter wheat in the typical plots in Shenzhen and Ningjin county accounted for 32.17% and 9.47% of the total evapotranspiration,and that of trees in summer corn in the typical plots in Shenzhen and Ningjin county accounted for 17.93% and 11.21%,respectively.The variation trend of soil water storage in typical plots is consistent with the influence of irrigation amount and rainfall amount.Moreover,the fluctuation range of soil water content in shallow layer is larger than that in deep layer.The greater the irrigation amount and rainfall are,the greater the fluctuation of soil water storage amount is.Deep leakage occurred in all typical blocks,among which,the deep leakage in typical blocks in Shenzhen city was 0-41.18 mm during the whole simulation period,and that in ningjin County was 0.02-6.51 mm.(3)In general,the rainfall effective utilization coefficient of typical plots in Shenzhen is greater than that in Ningjin County.For the growth period of winter wheat,the typical plot in Shenzhen was irrigated once,and the effective utilization coefficient of rainfall was the highest when the irrigation amount was 180 mm.In the typical plot of Ningjin County,the effective utilization coefficient of rainfall was the highest when the single irrigation amount was 105 mm.For the growth period of summer maize,the effective utilization coefficient of rainfall was the highest when the typical plots in the two counties were not irrigated.