华北地区主要作物灌溉制度优化及区域灌溉需水分析OA

Located in the low-lying Heilonggang region of the Haihe basin,Nangong City in Xingtai,Hebei Province,faces significant challenges,including agricultural water scarcity,uneven seasonal precipitation,irrational irrigation practices,and severe groundwater overexploitation. This study aimed to optimize irrigation schedules for winter wheat and summer maize in the region to enhance irrigation water use efficiency and reduce groundwater extraction.The data used for model construction and calibration primarily come from field investigations and experiments conducted in the study area.The research proceeds in three steps:model construction,model validation,and application of the model to irrigation scenario analysis.During the rate-setting process,actual field observations of soil water content,plant height,and yield from 2022 to 2023 were used to compare with the simulated data,and the more sensitive crop growth parameters were manually adjusted by trial and error in steps of 0.1 until R2 exceeded 0.75.After the rate-setting was completed,yield data from the relevant literature for 2016 to 2021 were used to further validate the model's validity in a multi-year simulation scenario.The model accuracy was verified using the coefficient of determination(R2),RE,RMSE of the simulated and measured values,and NRMSE.Based on the rate-setting and validated APEX model,11 irrigation regimes were further set up for winter wheat-summer maize,and the water use efficiency was calculated based on the crop yield and water consumption output from the model to determine the optimal irrigation quota.The water demand and consumption analysis of the area was carried out using model outputs for evapotranspiration,soil evaporation,and seepage,and an improvement plan was proposed based on the results. Results showed that:1)APEX model can simulate the growth of winter wheat and summer maize and the process of soil moisture change in the study area more accurately,and the R2 of the model-simulated soil water content,plant height and crop yield during the reproductive period of winter wheat and summer maize were all greater than 0.75 with the actual observation data,and the RE and NRMSE were less than 10%.2)Using the rainfall data from 2004 to 2023 to classify typical years,the highest water use efficiency was determined for winter wheat at the irrigation rates of 180,200,and 240 mm in the abundant,flat and dry years,which were 2.1,2.1 and 1.8 kg/m3,respectively.The highest water use efficiency was determined for summer maize at the irrigation rates of 49.5,82.5,and 115.5 mm in the abundant,flat and dry years,which were 2.6,2.4 and 2.3 kg/m3,respectively.3)The values of ET,E,and PRK for both crops,winter wheat and summer maize,showed a significant increasing trend in all three year types.The ET of winter wheat ranged from 312 mm to 429 mm,and that of summer maize ranged from 305 mm to 367 mm.The seepage volume increases with the irrigation volume.For winter wheat,it ranges from 19 mm to 122 mm,and for summer maize,it ranges from 11 mm to 89 mm.Moreover,The soil evaporation of winter wheat accounts for 27.5%to 31.4%of ET,and that of summer maize accounts for 26.7%to 33.6%.Crop transpiration is the main part of evapotranspiration.Water-saving technologies can be adopted to reduce evaporation and leakage and improve water use efficiency.4)With the optimized irrigation quota,the total water demand for agricultural irrigation of winter wheat and summer maize is 4.15×107,5.59×107 and 7.04×107 m3,respectively,which can be reduced by 30.9%,17.4%and 3.5%compared with the current situation. The optimized irrigation system and regional agricultural irrigation water demand calculation proposed by the research under the winter wheat-summer maize rotation model can provide a reference for the over-exploitation control of groundwater in Nangong City.