Groundwater and the Rising Seas

Did you know?

  • More than 50% of the US population lives near coasts. 
  • Since 1880, global sea level has risen about eight inches. Scientists expect global sea level to rise another one to four feet by 2100.

Groundwater is the water that fills empty spaces and cracks under the surface and above impermeable rock layers that supplies much of the US public and domestic water supply, supports agricultural and industrial economies, and contributes flow to rivers, lakes, and wetlands.

The amount of water that is stored underground varies across the US depending on the geology of the area, recharge (from sources such as precipitation, snowmelt, lakes, and rivers), and withdrawal from wells. If water is discharged at a rate that is greater than recharge, it is possible for groundwater to run out or become unusable in some areas. A changing climate impacts the quantity and quality of groundwater through increased risks of drought, changes in precipitation and temperature, decreases in snowmelt, and rising sea levels.

Groundwater in coastal regions of the US is particularly at risk due to a combination of changes in precipitation, withdrawal rates, and sea level rise. Along the coast, groundwater and saltwater from the ocean are naturally separated by the seaward movement of groundwater and a transition zone where freshwater and saltwater mix. As changes in precipitation and rises in sea level continue, the occurrence of saltwater infiltrating groundwater resources may increase and reduce the availability of freshwater for coastal communities. For example, the Biscayne Aquifer at the southern tip of Florida is the primary water source for the Florida Keys, Miami, and the lower east coast of Florida. As sea level rises, the amount of saltwater infiltrating the groundwater aquifer will increase, which can make the water too salty for human consumption.

Learn More:

  • Saltwater Intrusion

The image below demonstrates how sea level rise and overwithdrawing can contaminte groundwater.

Saltwater Intrusion
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  • Depletion of Groundwater in Major US Regional Aquifers

The graphs below from chapter 3 of the Fourth National Climate Assessment show how, "groundwater supplies have been decreasing in the major regional aquifers of the United States over the last century (1900–2000). This decline has accelerated recently (2001–2008) due to persistent droughts in many regions and the lack of adequate surface water storage to meet demands. This decline in groundwater compromises the ability to meet water needs during future droughts and impacts the functioning of groundwater dependent ecosystems."

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