Research indicates that the Southeast is currently experiencing the effects of climate change. The U.S. Global Change Research Program shows that average temperatures have risen 1.1°C since 1970 and that annual precipitation has increased between 20–30% since 1895. Importantly, regional temperature changes have been shown to be greater than global average changes, resulting in an increase in moderate to severe droughts over the last 30 years.
The U.S. Global Change Research program predicts an increase in the number of very hot days and an increase in annual temperatures between 2.5°C and 5°C by the end of the century. Summers are forecasted to be 5.8°C higher than current temperatures by 2100.
Warmer temperatures of this magnitude would have a number of effects on water resource managers. Most prominently, higher temperatures would increase evapotranspiration and cause longer periods of time between rain events, resulting in decreased stream flow and surface runoff. This would reduce groundwater recharge rates throughout the region. Higher average temperatures would reduce water availability and lower water quality, possibly forcing utility managers to develop new sources of supply, increase use of demand side management activities, and institute new treatment processes to ensure the quality of drinking water.
Future projections of hydrological change for the Southeastern United States are less certain. The most recent IPCC assessment contains climate change models that do not predict a clear precipitation trend in the future. However, preliminary conclusions drawn from these models include South Florida becoming wetter during the dry season and Eastern North Carolina becoming wetter during the dry season and dryer during the wet season.
The Southeast is also at risk for sea-level rise. Models project a range of sea-level rise over the next 100 years, with sea-levels forecasted to increase between 21.3cm and 48.8cm. This would threaten the quality of coastal water supplies throughout the region, since rising sea-levels can inundate freshwater resources and storm surges can impact surface water and utility infrastructure. Some water utilities are more vulnerable to sea-level rise than others. Vulnerable utilities are those using groundwater that is recharged in freshwater areas that are at risk of increasing salinity.
Overall, water utility managers must manage the threat to water supply and quality posed by warmer temperatures and sea-level rise. Many coastal areas throughout the Southeast that rely on groundwater and aquifers are at risk from salinization of freshwater resources. Rising seas may force water utility managers to develop new infrastructure to protect groundwater resources, explore new sources of supply, implement new water treatment processes, and develop desalinization treatment processes.