Response Between Crop Yield And Regional Water Resources

The North China Plain is the main grain production base in China.The grain production in this area will directly affect the grain supply in China.The shortage of surface water resources in North China and the long-term overexploitation of groundwater lead to the increasing groundwater depth.Crop growth is closely related to water conditions.In order to achieve the stability of agricultural production,it is necessary to analyze the impact of groundwater depth on crops and study the response of water resources under different planting structures.In this paper,the coupling model of AquaCrop and Visual MODFLOW was established in Shijin Irrigation District.The effects of different groundwater conditions on crop growth and yield response under future groundwater conditions were studied.From the perspective of water saving,the suitable planting structure of Shijin Irrigation District was sought.The main research work and achievements are as follows:(1)The establishment of the coupling model of AquaCrop and Visual MODFLOW.The establishment of AquaCrop model included five aspects:climate,crop,management,soil and simulation settings.In this paper,the output of Visual MODFLOW was used as the input of AquaCrop to study the response of crop yield to groundwater in the future.Visual MODFLOW simulated groundwater through time discretization,space discretization and hydrogeological parameter zoning.The results of model calibration and verification showed that the coupling model was reasonable.(2)The study on the effect of groundwater depth on crop yield included two aspects:current and future groundwater conditions.Under the current condition,the results of groundwater depth scenario in the whole growth period showed that the suitable groundwater depth in Shijin Irrigation District was about 2 m.Taking cotton as an example,the results showed that the most sensitive stage of cotton to groundwater depth was bud stage and flowering-boll stage.Under the future groundwater conditions,the Visual MODFLOW model was used to predict the future groundwater dynamic and set up six exploitation schemes to simulate.The response of yield to groundwater changes was studied by combining AquaCrop model.Based on the suitable groundwater depth,the exploitation schemes were optimized.The possibility of rain-fed agriculture was discussed.The results showed that summer maize was the only crops that can be rain fed.Under the most suitable groundwater depth,rain fed agriculture would reduce the yield of summer maize by about 10%.(3)Based on the analysis of the balance between supply and demand of water resources in Shijin Irrigation District,the optimization model of planting structure was established.Under the objective function of the minimum crop water consumption,the maximum economic benefit of crops,the minimum crop water consumption in rain-fed agriculture and the realization of water saving in winter wheat fallow,the planting structure was adjusted.The effects of the adjustment under the four objectives on groundwater resources were as follows:saving 31.67 million m~3,not affecting regional water resources,saving 33.33 million m~3,and saving 500 million m~3.