Saltwater Intrusion Vulnerability of Soil and Groundwater Near Estuaries
Hayden A. Tackley, Barret L. Kurylyk, Craig B. Lake
Abstract
ABSTRACT Estuaries and the soil and groundwater surrounding them are increasingly vulnerable to the compounding effects of climate change. Despite their societal and ecological importance, surprisingly little consideration has been given to the vulnerability of soil and groundwater systems adjacent to estuaries. Here, we use global datasets to identify the spatial extent of at‐risk land near estuaries and present a literature review on how changing estuarine surface water may impact soil and groundwater in these areas. Approximately 150,000 km 2 of agricultural land and 23 of the world's megacities are located in low‐elevation coastal zones close to an estuary. Future sea‐level rise, storm surges, drought, and increased evaporation will increase the surface water salinity in many estuaries, while oceanic and fluvial drivers will likely result in more flooding in these low‐elevation zones. The spatial and temporal variations in surface water dynamics and conditions of individual estuaries (e.g., geology, bathymetry, tidal range) result in complex and highly variable groundwater‐surface water interactions in these settings. Field and modeling studies have indicated that increased exposure to saline or brackish water during estuarine flood events will result in soil salinization and vertical saltwater intrusion into underlying aquifers. Increased surface water levels and salinity can also lead to the lateral, subsurface migration of saline water into estuary bank sediments, potentially contaminating groundwater used for irrigation and human consumption. The salinization of soil and groundwater near estuaries may result in food and water insecurity in areas not previously considered at risk of coastal climate impacts.