Study On The Interaction Between Surface Water And Ground Water In Qin River Basin Using A Distributed Hydrological Model

Physically based distributed hydrological models, which originated from the blueprint propounded by Freeze and Harlan, have been a focus in hydrology research. Spatial discretization can effectively represent watershed hydrologic heterogeneity. The parameters are determinately defined and can be measured by observations or experiments. So physically-based models can describe the mechanism of water resources formation under human activities and benefit watershed management and planning.Frequent interaction between surface water and groundwater exists in the Qin River basin, where layered karst regions lie in middle and lower reaches and the amount of ground water abstraction is large. Measured runoff shows a significant decrease in recent years. To understand the mechanism of the interaction of the natural runoff and groundwater, this dissertation proposes a Hydrological Similar Slope Units-based distributed hydrological model for a dynamic representation of hydrologic processes including interception, depression, unsaturated flow, groundwater flow, overland and channel flow routing, etc. The model includes a special seepage model for karst regions and can incorporate human activities.After calibration, the model is applied to Qin River basin for a long term simulation, declaring the mechanism of water resources formation and interaction between surface water and groundwater. The results show that Hydrological Similar Slope Units are effective and efficient for distributed hydrological modeling in large watershed. Present artificial water use in Qin River basin takes a relatively small part of the whole hydrologic circle and the reduced rainfall is the main factor affecting the water resources changes. More than 80% of the total groundwater resources coming from water exchange and groundwater overexploitation rapidly reduced the water table and natural runoff as a consequence. The Karst affects various processes in the whole hydrologic cycle and leads to dynamic evolution of the interaction between the surface water and ground water.