Dams Could Alter Local Weather, Cause More Rain

[The Straight Story]

Dams Could Alter Local Weather, Cause More Rain

As if America’s aging dams were not in enough trouble already, new research suggests that their reservoirs could be increasing the intensity of extreme rainstorms in their immediate vicinities.

That’s a problem because the dams were designed for the climate that existed in the area before they were built. If by virtue of their creation, they increase the chance that an extreme weather event will exceed the dams’ capacity, they could be less safe than previously thought.

“What if the dam itself, its reservoir, could have accelerated or intensified the heavy rainfall patterns?” said Faisal Hossain, a hydrologist at Tennessee Tech University, who has co-authored a paper and editorial on the topic accepted for publication in Natural Hazards Review and Water Resources Research, respectively.

There is strong evidence that a standing body of water, like a lake, can alter precipitation patterns, Hossain said. Increasing the amount of liquid water in a region increases the amount of evaporation in a region, too. That water vapor will eventually condense and fall as precipitation. So, it’s logical to think that a dam’s reservoir could have the same impact. And dams allow irrigation, which can transform the land in the area, possibly leading to local climactic impacts.

Marshall Shepherd, a research meteorologist at the University of Georgia, called the findings “interesting and plausible” in an e-mail to Wired.com.

http://www.wired.com/wiredscience/2009/12/dam-weather/

[msongs]

1. nice, dams act to fill their own reservoirs. nt

[Yo_Mama_Been_Loggin]

2. Damn

[amborin]

3. wish we could get rid of all of them; in CA, only the Cosumnes River is not damned n/t

[arcadian]

4. That's not rocket science.

Mow down a natural rain forest and watch that area turn to desert. I've seen it happen. In Hawaii, they cut down a huge swath of natural rain forest and put Mac nut trees up instead. Changed the climate for that part of the island into a desert.

[amborin]

5. horrible; and that's occurring all over Sumatra & other parts Indonesia, rain forest & bogs destroye

[damntexdem]

6. Just another dam problem, huh?

And the lakes behind dams can also seep into the water table.

On the other hand, without the damns, streams may keep wetlands flooded more of the year, so do a lot more with spread-out surface water versus a deeper lake behind a dam.

[L0oniX]

7. ...so could an Indian rain dance.

[FBaggins]

8. That makes little sense.

Any additional rainfall due to evaporation over the larger water-surface of the reservoir would be water that had left the reservoir in the first place.