The sea-level rise that accompanies climate change will reduce the freshwater supply in many coastal communities by 50% more than previously thought, as sea water infiltrates groundwater and renders it brackish and undrinkable.
“Most people are probably aware of the damage that rising sea levels can do above ground, but not underground, which is where the fresh water is,” says Motomu Ibaraki, associate professor of earth sciences at Ohio State University. Coastlines, according to Ibaraki, are made up of many different layers and kinds of sand. Fine sand tends to hold up against water, but coarse sand lets water through where it can reach underground springs and create brackish water.
In his study presented to the Geological Society of America, Ibaraki showed that, depending on the sand composition of the shoreline, brackish water can extend as much as 50% further inland than saltwater on the surface. Ibaraki hopes to create a world salinity hazard map showing which areas have the potential for the most groundwater loss due to sea-level rise.
The way we use-and often abuse-freshwater supplies will have a growing impact on a variety of life and health issues, says Ibaraki. He speculates that freshwater loss due to sea-level rise, agriculture, water transfer, and overuse could create global food shortages in the years ahead. Desalination is key to ensuring supplies of drinkable water, but it’s an energy-intensive process. Very little of the world’s energy use is climate friendly, so dealing with water shortages could exacerbate the process that caused the shortage in the first place.
“Our energy use now could reduce the availability of freshwater and groundwater through the climate change process,” he says. “These resources are decreasing due to human activities and population increase.”
Another approach to protecting water supplies is “to transfer water from regions that have it in abundance to regions that face water shortage. Unfortunately, both approaches require energy. The cities that can access seawater might desalinate it but others will [be forced to] recycle water within cities and greatly reduce individual water usage.” Water recycling is impossible when water is used for agriculture, which accounts for more than 80% of consumptive water use in the United States.
Originally published in THE FUTURIST, March-April 2008.