Effects of Groundwater on Salinization of Coastal Reservoir - IAHR World Congress, 2019 Water Connecting the World

Guangqiu Jin ^1,2 Yuming Mo ^1,2 Hongwu Tang ^1,2 Kai Jin ^1,2 Ling Li ^1,2 D.A. Barry ³

¹State Key Laboratory, Hohai University, Hydrology and Water Resources and Hydropower Engineering, China
²College of Water Conservancy and Hydropower Engineering, Hohai University, College of Water Conservancy and Hydropower Engineering, China
³Institut d’ingénierie de l’environnement (IIE), Faculté de l’environnement naturel, architectural et construit (ENAC), Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratoire de technologie écologique (ECOL), Switzerland

Coastal reservoir provides the additional storage capacity of freshwater in coastal zone which greatly alleviate the water shortage in stressed areas, and the salinization of reservoir water degrade the utility of coastal reservoir which was the major challenges that coastal reservoir faced. Salinization may result from two major reasons: (a) inadequate desalinization in early operation stage and (b) seawater intrusion in normal stage, and groundwater as the important source of freshwater to coastal reservoir and adjacent aquifer was obviously have significant impacts on salinization which was in a dearth research. Laboratory experiments were conducted to further discuss the influence of groundwater on the desalinization and seawater intrusion. The results from experiments shown that coastal reservoirs could greatly alleviate the seawater intrusion in coastal aquifer because coastal reservoir could prevent the seawater from submerging the intertidal zone. With the groundwater discharge rate increased, saltwater wedge result from intruded seawater was further moderated in seawater intrusion cases. Coastal reservoirs also greatly changed groundwater discharge pathways to sea. Without coastal reservoir, groundwater discharge to sea directly, while with coastal reservoir, part of groundwater would firstly discharge to coastal reservoir, desalinate the reservoir water, and then to sea. The time it takes for the laboratory experiments from beginning to quasi-state was also decreased with groundwater discharge rate increased. Mathematical model was designed for the prediction of the salinity of reservoir water, and the results from model could indicate the accuracy groundwater discharge pathways in coastal reservoir and adjacent aquifer. These results demonstrate the complexity of the groundwater system in adjacent aquifer of coastal reservoir, and may have great implications for future investigations on the predication of water quality during the full operational period.