Threat Posed by Future Sea-Level Rise to Freshwater Resources in the Upper Pearl River Estuary

The degradation of densely populated river delta environments due to the accelerating rise in sea level can affect the availability of freshwater for municipal supplies, irrigation, and industrial use. A fully calibrated three-dimensional numerical model is used in this study to evaluate the threat posed by the sea-level rise, which predicted to occur by 2100, to freshwater resources in the upper tributaries of Pearl River Estuary. The results indicate that both the intensity and duration of dry-season saltwater intrusion greatly increase as the sea level rises, making the water at drinking-water intake stations for the four waterworks no longer suitable for municipal supply. Flow modulation is performed to identify the threshold at which saltwater intrusion could be effectively suppressed in response to both sea-level rise and dry season hydrodynamics. The number of days for which water meets the drinking-water standard decreases as the sea level rises, but increases with increased river flow. The combined effect of future drought and sea-level rise would further limit the availability of freshwater in the upper tributaries. Stronger upstream salinity transport during flood tide are found in the sea-level rise case. The increased flood tidal salinity transport would have great impact on the tidal freshwater wetlands.