Water supplies could be strongly affected by climate change

MIT News: It's no simple matter to figure out how regional changes in precipitation, expected to result from global climate change, may affect water supplies. Now, a new analysis led by MIT researchers has found that the changes in groundwater may actually be much greater than the precipitation changes themselves.

For example, in places where annual rainfall may increase by 20 percent as a result of climate change, the groundwater might increase as much as 40 percent. Conversely, the analysis showed in some cases just a 20 percent decrease in rainfall could lead to a 70 percent decrease in the recharging of local aquifers -- a potentially devastating blow in semi-arid and arid regions. But the exact effects depend on a complex mix of factors, the study found -- including soil type, vegetation, and the exact timing and duration of rainfall events -- and so detailed studies will be required for each local region in order to predict the possible range of outcomes.

The research was conducted by Gene-Hua Crystal Ng, now a post-doctoral researcher in MIT's Department of Civil and Environmental Engineering (CEE), along with King Bhumipol Professor Dennis McLaughlin and Bacardi Stockholm Water Foundations Professor Dara Entekhabi, both of CEE, and Bridget Scanlon, a senior researcher at the University of Texas. The results are being presented Wednesday, Dec. 17, at the American Geophysical Union's fall meeting in San Francisco.

…"What we found was very interesting," Ng says. "It looks like the changes in recharge could be even greater than the changes in climate. For a given percentage change in precipitation, we're getting even greater changes in recharge rates."

Among the most important factors, the team found, is the timing and duration of the precipitation. For example, it makes a big difference whether it comes in a few large rainstorms or many smaller ones, and whether most of the rainfall occurs in winter or summer. "Changes in precipitation are often reported as annual changes, but what affects recharge is when the precipitation happens, and how it compares to the growing season," she says….

Rainstorm and a sunset, NOAA