What Happens When Seawater Invades Freshwater Aquifers?

October 17, 2016 – In a paper published in Geophysical Research Letters last month, researchers at University of South Florida, Michigan Technological University, University of Florida, and Auburn University, describes the impact of rising seas on freshwater sources on islands. Their conclusions – “rising seas will cause them to lose their fresh water by pushing it above ground, where it gets evaporated.”

In the study the researchers simulated islands in the southern part of The Bahamas which get almost all of their freshwater from precipation. They noted that as sea levels rise so did groundwater causing surface lakes to expand and new ones to form. This sped up evaporation.

Shannon Sterling of Dalhousie University in Halifax, Nova Scotia, is not one of the authors of the research. She notes that the consequences for islands could ve severe stating, “this new mechanism will affect large areas of the planet or have measurable changes to the global water budget, but because reductions in available water are occurring in already water-limited sensitive areas, with potentially large economic and human consequences.”

The study could have implications for more than islands. Rising sea levels are introducing saltwater into freshwater aquifers in places like Florida. Florida has spent billions of dollars to stop the phenomenon from contaminating drinking water and water used for industrial and agricultural purposes. The South Florida Water Management District has installed reverse osmosis plants to convert brackish water that has intruded into the deep water aquifer.

In addition rainwater conservation mechanisms have been put in place to ensure adequate freshwater supplies for this part of Florida which is home to significant urban growth. Areas most impacted are Miami-Dade County where low elevations and rising sea levels are causing saltwater creep in the aquifer. The state has implemented a $4.1 billion potable water plan to fight what scientists believe will be a growing challenge as climate change impacts sea levels.

States Barry Heimlich, a retired engineer with a background in the petroleum and pharmaceutical industries, “As the sea level rises, saltwater pushes inland like a parabolic curve – the deeper you go the more saltwater there is and it moves inland…..some wells have become contaminated and were moved inland and that will probably continue. Even a small amount of sea rise can have a very large effect.”