| The ecological water replenishment of Yongding River is carried out to rebuild the ecological corridor and revive the ecological environment of rivers and lakes.Ecological water replenishment not only affects the dynamic characteristics of surface water in the upper reaches of yongding River but also has a potential impact on groundwater dynamics and surface water-groundwater exchange characteristics.To explore the interaction between surface water and groundwater before and after the ecological water replenishment in Yongding River,and to quantify the response of surface water-groundwater exchange characteristics to different ecological water replenishment schemes,this paper constructed a surface water-groundwater coupling model based on HEC-RAS and MODFLOW.The Picard iterative method was used to reduce the water residuals of the coupled system,and then the model was calibrated and calibrated.The model was used to analyze the surface line and surface area,groundwater balance,exchange capacity,and the rate of surface water-groundwater system in dongshagou to Shixiali section of the upper reaches of Yongding River before and after the ecological water replenishment.Based on the characteristics of ecological water replenishment in spring,9 water replenishment conditions were constructed and simulated,and the following conclusions were drawn:(1)Dynamic characteristics of surface water.Before the implementation of ecological water replenishment,the distribution of channel water depth in the study area of the upper reaches of Yongding River presented fault and non-uniformity.After the implementation of ecological water replenishment,the length of the water-flowing channel and the depth of the channel had increased significantly.Due to the difference in water quantity and leakage loss,the water surface rise and fell steeply in spring,while the variation of river surface line in autumn was more stable than that in spring.(2)Dynamic characteristics of groundwater.From 2013 to 2017,the average rise of groundwater level in the study area was 0.6 m.After the implementation of ecological water replenishment,the average rise of groundwater level was 4.7 m,and the rise of groundwater level in some regions was more than 7 m.The variation rate of groundwater level in the study area was 0.002 to 0.045 m/d,and the underground aquifer was in a recharge state.(3)Exchange characteristics of surface water and groundwater.Before the implementation of ecological water replenishment,the exchange capacity of surface water and groundwater ranged from-15.07 to-199.02 m~3/d,and the exchange rate of surface water and groundwater ranged from-0.09 to-0.33 m/d,except where the Huliu River entered.After the implementation of ecological water replenishment,the exchange capacity ranges from-163.9 to-582.3 m~3/d,and the exchange rate ranges from-0.194 to-0.465 m/d,except where huliu River enters.(4)The influence of spring ecological water replenishment conditions on surface water-groundwater exchange characteristics.Under the same condition of early water flow,the greater the later water flow,the greater the river leakage.The exchange capacity of surface water and groundwater was in the range of-4.8 to-236.5 m~3/d,and the exchange rate was in the range of-0.001 to-0.048 m/d.At present,the replenishment and drainage relationship between surface water and groundwater under spring replenishment conditions was dominated by the infiltration and replenishment of surface water to groundwater,and the replenishment amount was 2.0 to 4.7 times the output.It was suggested that high water flow should be adopted in the early stage of ecological water replenishment in spring,and it can be appropriately reduced to medium and low water flow in the later stage. |
