Development of a River Hydrodynamic Model for Studying Surface-Ground Water Interactions Affected by Climate Change in Heihe River, China

Over the past 50 years, glacier area in Qilian Mountain of the Heihe River basin has decreased by 29.6%, mainly resulting from the climate change. Understanding the interactions of surface and ground water interaction will be very helpful for studying climate-change impact on Hehei River basin. This paper presents the development of one-dimensional river hydrodynamic model for surface and ground water interactions (RHM-SG). Surface-water flow is described by the modified one-dimensional Saint Venant equations, which is solved by Preissmann scheme. The flow exchange between surface and ground water is described by Darcy's equation. Five model validation tests include uniform flow over sloping bed, one flood process, and river flow with interactions of ground water. Model tests demonstrate that the model compares well with analytic solution, and reasonably characterize the interaction between river flow and ground water. The model has also been tested in the application to the middle reach of the Heihe River. By including surface-ground water interactions, the accuracy of model predicted flow substantially improves. The correlation coefficient increases from 0.89 to 0.98, and the root-mean-square reduces from 21.16 m(3)/s to 8.49 m(3)/s, respectively.