Dams Could Protect Ranchers From Climate Change’s Drought…But Could They Also Contribute To It? — #Wyoming Public Media

Avalanche debris Middle Piney Dam. Photo credit: USFS

From Wyoming Public Media (Melodie Edwards):

There are lots of things to be stressed about in ranching, and one of the big ones is water. [Chad] Espenscheid says that’s why he’s glad the state is fixing up the Middle Piney Dam. It’s fallen into disrepair at the top where the creek flows into the Green River.

“It would give Middle Piney Creek a little more of a steady flow instead of it all coming out in one shot and everybody really having to hustle around and capture it all at one time,” Espenscheid says…

Not only is Espenscheid a rancher, but he’s also a water engineer and participates in an experimental water conservation program that pays ranchers to only irrigate when they have to. So in late summer after he’s hayed his fields he turns off the spigot. But Espenscheid says, fixing that dam will store a modest 4,200 acre-feet of Colorado River water.

He’s not sure what to think about how siphoning that small amount out of the river will affect lower basin states that also rely on the Colorado River. “I don’t know, I’m just Wyoming through and true, so I’m kind of worried about Wyoming, I guess to be honest. So, I think we’ve got to take care of our own sustainability and make sure we have opportunities for growth.”

It’s not just the Middle Piney Reservoir that’s going to start dipping from the Colorado, though. Jason Mead at Wyoming’s Water Development Office adds up all the acre-feet of water storage the state wants to build on the Green River drainage: “4,000 for Middle Piney, 10,000 for West Fork, that’s 14,000. Another eight at New Fork, so that’s 22,000, another nine between Meek’s Cabin, that’s 31,000….”

[…]

All told, he figures Wyoming could tack on about 50,000 acre-feet on five new or expanded reservoirs, including Big Sandy, West Fork, Meek’s Cabin and Stateline. And then there are the 80,000 acre-feet that the Fontanelle Reservoir could eventually add. (The plan there is to complete that project when extreme drought draws it down low enough to finish its foundation.)

At 130,000 acre-feet total that would be enough water to supply a city of a million people, but the population of the entire state of Wyoming is half that.

“Every one of these projects we’re talking about really are for irrigation shortages and trying to handle the drought situations that everybody has faced over the years and trying to take water when we have good years and carry it over into years that are drier,” says Mead…

Mead says more dams could help ranchers survive the coming droughts, but some scientists say, building more dams might actually worsen climate change. University of Wyoming soil scientist Jay Norton says, dams that manage for flood control, for example, could have a damaging effect.

“They want the water drained out so in the event of a flood they have storage capacity,” he explains. “That can cause very low flows downstream that dry up those flood plain wetlands.”

Norton says those wetlands store huge amounts of organic carbon.

“There’s estimates that if we could raise soil organic carbon by about 0.4 percent per year that we would completely offset human-derived emissions of greenhouse gases.”

Think of all the plants growing like a green snake along streams in the otherwise arid Mountain West. Wetlands on undammed waterways can take up as little as two percent of the landscape but hold 15 to 30 percent of the carbon. But if reservoirs hold back all the water those green snakes will dry up and stop holding carbon.

But, Norton says, managed correctly, more dams in the upper basin states could actually create more wetlands and store more carbon.

“Conceivably, it could have a positive effect on downstream wetlands, if water tables are maintained relatively high,” says Norton. “Irrigation itself expands wetlands.”

Unfortunately, that’s not the only effect of dams on climate. One study shows that decomposing organic matter behind dams as the water level drops can produce large amounts of methane, a greenhouse gas that’s even more potent than carbon dioxide.

But Rancher and Water Engineer Chad Espenscheid says the positives of building dams outweigh the negatives.

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