PATTERNS OF SUBMARINE GROUNDWATER DISCHARGE REVEAL COASTAL VULNERABILITIES

Submarine groundwater discharge (SGD) delivers water and dissolved chemicals from continents to oceans, and its spatial distribution impacts coastal water quality. Unlike rivers, SGD is broadly distributed and relatively difficult to measure, thus continental-scale patterns of SGD are poorly known. We present spatially resolved estimates of fresh (land-derived) SGD for the contiguous United States based on historical climate records and high-resolution hydrographic data. Climate controls regional patterns in fresh SGD, while coastal drainage geometry imparts strong local variability. Because recharge zones for fresh SGD are densely populated, the quality and quantity of fresh SGD is vulnerable to anthropogenic disturbance. Our analysis unveils hot spots for contaminant discharge to marine waters and saltwater intrusion into coastal aquifers.