Assessment of seawater intrusion potential from sea-level rise and groundwater extraction in a coastal aquifer

Abstract: Groundwater is an important water resource in many coastal areas around the world. Excessive pumping can change the flow pattern so that seawater may migrate into the freshwater aquifer. In addition, the rise of the sea level due to climate change could accelerate the landward intrusion of seawater. This study addresses the problem of variable-density groundwater flow and miscible salt transport to assess the potential of seawater intrusion in coastal aquifers. Our conceptual model considers a complete hydrogeologic system including the river system, the seasonal groundwater recharge, the groundwater pumping, and the interaction between seawater and groundwater. Model calibration is performed using the covariance matrix adaptation–evolution strategy as a robust derivative-free global optimization algorithm. The advantage of this algorithm is its ability to reach a near global solution in solving the groundwater inverse problem, which is typically nonlinear and ill-posed. Simulations for the Nam Dinh Province, Vietnam over the period of 90 years indicate that seawater intrusion will occur, but the extent of it will vary depending on scenarios. The extraction of groundwater is the key factor governing the intrusion of seawater. The magnitude of seawater intrusion caused by rising sea level sturned out to be relatively small. Sensitivity analysis reveals that uncertainties of transport parameters could significantly affect the assessment of seawater intrusion potential.