| Since the 1980s,drought has intensified in the North China Plain,and the runoff from the upper reaches of the Baiyangdian Lake has been greatly reduced.The Baiyangdian Lake is facing dry lake and ecological crisis.In order to maintain the healthy water level of the baiyangdian Lake ecological environment,after the establishment of the Xiong’an New Area,the South-to-North water diversion project for ecological water replenishment to the Baiyangdian Lake.The water of the South-to-North water diversion project through the Baohe reservoir regulation and storage,and through the Baohe river to the Baiyangdian Lake.The Baohe River is a seasonal river,except for the occurrence of heavy rain in the upstream,there is no steady runoff in the river.The groundwater depth in the plain area of the Baohe River basin is more than 20m,and the groundwater is resupplied by the runoff of river surface water in the process of water replenishment,resulting in low efficiency of water supply to the Baiyangdian Lake.In addition,the study area is also a key area of groundwater overexploitation control,and it is an urgent task to coordinate the contradiction between water delivery and water replenishment.Therefore,to explore the Surface water and groundwater conversion in the Baohe plain area of the upper reaches of the Baiyangdian Lake and how to improve the efficiency of water transfer from the South-to-North water diversion project to the Baiyangdian Lake has become a problem of close social attention.In this paper,the conversion of surface water and groundwater and the numerical simulation of ecological water replenishment in the Baiyangdian Lake were studied in the plain area of the Baohe River basin.The main research contents and achievements are as follows:(1)Groundwater dynamic characteristics and groundwater equilibrium analysis in plain area of the Baohe River Basin.This paper taking the Baiyangdian Lake upstream the Baohe river basin plain as the research area,based on the research area of runoff observation data and the long-term observation data of groundwater,driving force through the principal component analysis and model calculation,the annual dynamic changes and the years of the groundwater in the study area,surface water and groundwater conversion process influence factors and its driving forces were analyzed,and then through the establishment of equilibrium model of groundwater,The quantitative analysis of surface water and groundwater conversion in the study area provides data support for the calibration and validation of the coupling model of surface water and groundwater in the study area.Through research and analysis,it is concluded that the main influencing factors of groundwater dynamic change in the study area are agricultural irrigation and ecological water replenishment,and the groundwater dynamic process is significantly affected by human factors,and the groundwater in this area shows a typical dynamic characteristics of exploitation.The main factors affecting the conversion process of surface water and groundwater include riverbed characteristics,basin geology and geomorphology,hydrological regime and human activities.According to the calculation of groundwater equilibrium model,the total groundwater recharge and total excretion in the study area in 2018 were 51一0.92×104m3 and 4195.28×104m3,the difference of recharge and discharge was+915.64×104m3,and the groundwater storage variable was+1013.54×104m3,and absolute equilibrium error was-97.90×104m3.The relative equilibrium error is-1.92%,and the overall positive equilibrium state.(2)Study on joint numerical simulation of surface water and groundwater in the Baohe River Plain area.This paper based on the analysis of hydrology,meteorology,soil,land use,surface elevation,hydrogeology,and the structural characteristics and connection status of each aquifer in the Baohe River Plain area of the upper reaches of the Baiyangdian Lake,the SWAT-GMS coupling model of surface water and groundwater in the Baohe River Plain area of the upper reaches of the Baiyangdian Lake is established.The groundwater recharge and diving evaporation of the SWAT model simulation and Recharge module and evaporation module in GMS groundwater model combination,and calibrate the important parameters of the model based on actual observed data data,numerical simulation on surface water and groundwater transformation in research areas,the simulation results are used to analyze the conversion between surface water and groundwater.The coupling model takes 2018 to 2019 as the calibration cycle period,and 2020 to 2021 as the validation cycle period.The simulation results of the coupling model and the actual observation data during the validation period are compared and analyzed,and the error between the calculated values of the model and the observed values is small,which meets the simulation requirements.The SWAT-GMS surface water and groundwater coupling model simulation results show that the total groundwater recharge and total groundwater output in the Baohe River Plain area in 2018 were 5228.66×104m3 and 4278.00×104m3,showing a positive equilibrium on the whole.the difference of recharge and discharge was +950.65×104m3,and the groundwater storage variable was+1013.54×104m3,and absolute equilibrium error was-62.89×104m3.The relative equilibrium error is-1.20%,and the overall positive equilibrium state.(3)Groundwater flow calculation model based on SWAT-GMS and artificial neural network model prediction.The change trends and laws of groundwater level and flow are important basis for the scientific planning and reasonable management of groundwater in the Baohe River Plain area of the upper reaches of the Baiyangdian Lake.In order to obtain a more accurate 3D groundwater flow model,a groundwater flow calculation(GFC)model was established based on the SWAT-GMS surface water and groundwater coupling model in the Baohe River Plain area of the upper reaches of the Baiyangdian Lake.This paper analyzed the periodic groundwater recharge,the tridimensional flow space,the complex streamline combination,and the groundwater flow direction,and the pretreatment process of groundwater flow parameter data is also given.Based on this,the paper built an improved grayscale-embedded BP neural network to predict the groundwater flow,considering the method under the influence of external environment on the water,puts forward the antiinterference correction coefficient of the model,and by using Markov model to validate the value of the correction factor.The traditional neural network and the neural network proposed in this paper are used for training and testing.The prediction results are analyzed,and the mean square error of the prediction results of the traditional neural network is 8.48.The mean square error of prediction results of the method proposed in this paper is 1.42,and the relative error of prediction is smaller and the accuracy is higher.This study can provide data and theoretical support for scientific planning and rational development of groundwater in plain area of the Baohe River Basin,which provides reference for groundwater flow prediction and groundwater evaluation in the upstream plain area of the Baiyangdian Lake.(4)Numerical simulation and analysis of ecological water replenishment in the Baiyangdian Lake.According to the above research content,through the analysis of the ecological water demand and water replenishment channels of the Baiyangdian Lake,it is concluded that the ecological water replenishment of the Baiyangdian Lake through the South-to-North water diversion project is within 15000×104m3,combined with the actual situation of ecological water replenishment to the Baiyangdian Lake from the South-toNorth water diversion project in the 2018 to 2021.Therefore,this paper designs three schemes for ecological water replenishment of the Baiyangdian Lake through the South-toNorth water diversion project,which are 7000×104m3,10500×104m3 and 14000×104m3 respectively.The SWAT-GMS coupling model of surface water and groundwater in the Baohe River Plain area to simulate the three schemes under different water delivery time and different flow,and the optimal water replenishment scheme under the three conditions was obtained.Scheme 1:when the South-to-North water diversion project supply water to the Baiyangdian Lake 7000×104m3 in December,the water flow of the exit sluice is 10m3/s,the water flow of the Baohe reservoir is 7m3/s,the ecological water supply efficiency is the highest,at this time,the South-to-North water diversion project supplies water to the Baiyangdian Lake,and the amount of water enter the Baohe reservoir is 5268.50×104m3,the amount of water enter the Baiyangdian Lake is 3900.52×104m3,the water transport efficiency is 55.72%.Scheme 2:when the South-to-North water diversion project supply water to the Baiyangdian Lake 10500×104m3 in December,the water flow of the exit sluice is 10m3/s,the water flow of the Baohe reservoir is 7.5m3/s,the ecological water supply efficiency is the highest,at this time,the South-to-North water diversion project supplies water to the Baiyangdian Lake,and the amount of water enter the Baohe reservoir is 7666.44×104m3,the amount of water enter the Baiyangdian Lake is 5614.98×104m3,the water transport efficiency is 53.48%.Scheme 3:when the South-to-North water diversion project supply water to the Baiyangdian Lake 14000×104m3 in November,the water flow of the exit sluice is 10m3/s,the water flow of the Baohe reservoir is 7.5m3/s,the ecological water supply efficiency is the highest,at this time,the South-to-North water diversion project supplies water to the Baiyangdian Lake,and the amount of water enter the Baohe reservoir is 10051.98×104m3,the amount of water enter the Baiyangdian Lake is 7084.63×104m3,the water transport efficiency is 53.48%. |
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