"Submarine Groundwater Discharge: What is it and who cares"

"Submarine Groundwater Discharge: What is it and who cares"

Submarine groundwater discharge (SGD) is any flow of groundwater (or pore water) up across the seafloor. SGD has been reclaimed in some areas to augment the freshwater supply, but in many places SGD is a diffuse, but important, supplier of nutrients influencing coastal habitats and ecosystems.

We recently completed a series of experiments on assessing SGD at six sites: Australia, New York, Venice, Florida, Brazil and Mauritius. SGD is ubiquitous, but can be expected to be highly variable in both time and space.

The interpretation of diverse results raised issues concerning (a) the mixing of salt water and freshwater which often occurs in a ratio exceeding 10:1 and (b) discrepancies between measurements of large SGD and the calculations of mathematical models which tend to give much lower values. Each situation was complicated both by the nature of site-specific geology, and the importance of human impacts. Dredged channels, pilings and other alterations can enhance SGD.