Effects Of Water Inflow Chang Of Gangnan And Huangbizhuang Reservoir Watershed On Crops In Irrigated Area

Agriculture is the field most subject to climate and weather.Under future climate conditions,north China will see a significant rise in temperature,a decline in rainfall,a prominent contradiction between water supply and demand,and a continuous decline in the proportion of agricultural water use,which will have a great negative impact on agricultural production and food security.In this paper,the Gangnan and Huangbizhuang reservoir basins and the Shijin irrigation area were selected as the study area,and the SDSM model,SWAT model and Aqua Crop model were coupled to study the effects of changes in irrigation water and natural incoming water on the yields of three major grain crops,winter wheat,summer maize and cotton,in the Shijin irrigation area under future climatic conditions,and the main research work and results of the paper are as follows.(1)The SDSM model was used to predict the future climate change in Gangnan and Huangbizhuang reservoir basins.The results showed that the maximum and minimum temperatures increased significantly under RCP2.6 and RCP8.5 climate models,and the spatial distribution was higher in the south and lower in the north.Rainfall decreased at first and then increased,with a decrease of 66.8mm and 46.5mm under the two climate scenarios,respectively.The spatial distribution of precipitation was larger in the east and south,and smaller in the west.(2)By coupling SDSM model with well-modulated SWAT model,the temporal and spatial distribution trends of blue and green water in Gangnan and Huangbizhuang reservoirs in the future from 2025 to 2100 were studied.Run analysis method and frequency analysis method were used to analyze the persistence of the state of abundant and dry water and the combination analysis of abundant and dry water encounter.The risk of reservoir water supply under future climate conditions is also evaluated.The results showed that compared with the baseline period,the blue water quantity decreased and the green water quantity increased under the future climate scenario,and the green water resource quantity increased significantly under the RCP8.5 climate scenario.The persistence of the two reservoirs is weak when they are in normal water state,and relatively strong when they are in wet and dry water state.In the synchronous frequency of full and dry,the frequency of the same flat is the smallest,the frequency of the same dry is the next,and the frequency of the same full is the largest.The water supply risk is 0.616 under RCP2.6 and 0.612 under RCP8.5.(3)Aqua Crop model with fixed utilization rate was used to quantitatively analyze the impact of water quantity change on crops in Shijin irrigated area under different water supply reduction conditions,and to analyze the yield change of main grain crops in the irrigated area under future climate and irrigation conditions.The results showed that under RCP2.6 climate scenario,when water supply was cut by 30% and DRI was reduced to 0.499,crops in Shijin irrigated area would be reduced by 104,770 tons.Under the RCP8.5 climate scenario,when water supply was reduced by 35%,the comprehensive risk index was reduced to 0.493,and the crop yield in Shijin irrigated area was reduced by 135,17 tons.Under RCP2.6 and RCP8.5 climate scenarios,crop yield decreased by 75,460 and 83,150 tons,respectively,when irrigation conditions changed but climate conditions remained unchanged.When the climate conditions changed but the irrigation conditions remained the same,the yield decreased by138,120 tons and 160,79 tons under the two climate scenarios,respectively.When climate conditions and irrigation conditions were changed at the same time,the yield decreased by 173,720 tons and 191,910 tons respectively under the two climate scenarios.