Carolinas water managers brace for a drier – or sometimes wetter – climate future

The water managers, farmers and scientists meeting in Charlotte this week aren’t just figuring out how to cope with a dry future in a warming world. They will also have to handle deluges.

Climate change experts say flooding from intense rainfall will increase along with more frequent droughts in the Southeast.

A “wall of water” flooded South Carolina last October in the worst weather disaster to hit the state since Hurricane Hugo in 1989. Parts of Louisiana saw more than two feet of rain in three days last month.

Preparing for that future drew 260 people to the Carolinas Climate Resilience Conference, a 30 percent increase from the initial conference in 2014. It ends at Hilton Charlotte University Place on Wednesday.

Climate assessments predict that rising temperatures will evaporate more freshwater as competition for it grows in the Southeast.

“In the long view, climate is going to be a very challenging problem for water resources. Too much, too little, wrong times,” Susan White, executive director of UNC Chapel Hill’s Water Resources Research Institute, said in an interview.

Short term, she said, bursts of heavy rainfall are “going to cause a lot of problems, and that’s flooding. We’ve seen this in Charleston and in North Carolina on the coast.” Rising sea level will amplify flooding on the coast.

That’s prompting coastal cities like Charleston to prepare for a wetter future as local officials inland adapt to growing demand for water. Both are defined as building resilience. To those officials, it matters little whether the cause is climate change or natural variations.

“These type of conversations are at the very local level, individuals and communities moving forward with how they’re going to get water to their people,” White said. “It doesn’t necessarily have an overlay of climate (change) for them – they have to deal with what they have right now, in their immediate future and projections. Communities are actively planning for how to manage too much or too little.”

Carolinas water utilities are increasingly collaborating on long-range water forecasts, conservation measures and drought response plans.

Utilities in the Charlotte region factored in climate change for the first time in a recent 50-year study of water supplies from the Catawba River, which supplies Charlotte.

Evaporation takes an estimated 300 million gallons of water from Catawba reservoirs on a hot summer day. If local temperatures rise 3.2 degrees by 2065, as the plan estimates, water loss would go up 11 percent – an additional 33 million gallons daily.

Duke Energy, which manages the Catawba and other Carolinas rivers that supply water to 2.5 million people, has noted increasingly sparse rainfall since the late 1990s. At the same time, rain often falls with more intensity, in a matter of hours instead of days.

The other end of the water spectrum is drought. While the Carolinas have endured two record droughts so far this century, studies show deeper ones have occurred in distant centuries.

“I don’t need to wait for the (climate change) models to get better,” Durham water resources planner Sydney Miller told the conference. “I can look at the past and be very concerned about climate variability, and it doesn’t matter who’s causing it.”

This story was originally published September 14, 2016 at 12:30 PM with the headline "Carolinas water managers brace for a drier – or sometimes wetter – climate future."