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As Climate Change Pushes Runoff Earlier, Water And Colorado Ag No Longer Cleanly Overlap

Lance Cheung
U.S. Department Of Agriculture
The City of Greeley's Milton Seaman Reservoir, which is fed by the north fork of the Poudre River. Storage proponents agrue that new reservoirs should be built, others expanded, to ensure water availbility in drier times.

At Ollin Farms in Longmont, Mark Guttridge is transitioning from spring crops to vegetables that will ripen in late summer and early fall. Having water later in the summer is crucial for Guttridge, but he knows from experience that that's not guaranteed.

"In 2012, we were in a drought year and it got hot really early just like it did this year in June," he said.

Guttridge uses a combination of ditch and municipal sources to irrigate his 10 acres. The municipal tap is a partial safety net. The part of the farm that relies on water being available in the ditch... that's more vulnerable. Climate change means water from spring runoff is coming earlier, creating new challenges for farmers.

Researchers say climate change is already affecting Colorado agriculture, but not necessarily in the way people might expect. Both farmers and climate researchers are less concerned about there being enough water. For climate researchers like Jeff Lukas, a Colorado and Wyoming research integration specialist with the Western Water Assessment, the concern is when that water is available.

"By shifting the runoff anywhere from a couple of weeks to as much as a month earlier, they may be out of priority for their water rights and may not be able to utilize all or some of their water rights as a result."

"We have the most confidence that the annual cycle of snowmelt and runoff continue to shift earlier," Lukas said.

In 2014, Lukas led the revision of the WWA's 2008 Climate Change in Colorado report [.pdf] to the Colorado Water Conservation Board. He said there has been a trend toward earlier spring snowmelt and runoff over the past 30 years that can be directly attributed to climate change.

"Runoff will continue to shift earlier and then the low stream flows that we naturally get in late summer will also expand their season and so we'll see even lower summer stream flows," Lukas said.

That scenario means water may not be available for farmers like Guttridge. During the 2012 drought year, there wasn't a lot of water coming down the irrigation ditch at Ollin Farms by the end of August. The result was a loss of crops that rely on late season water like winter squash and pumpkins. What the Western Water Assessment and Lukas foresee is "an increasing mismatch" between the available water flowing downstream and agricultures needs over a long growing season.

The timing of water is crucial if you look at it through the prism of Colorado's prior appropriations water rights, said Taryn Finnessey, a climate change risk management specialist with the Colorado Water Conservation Board. Those rights give senior rights holders the ability to take water first.

"By shifting the runoff anywhere from a couple of weeks to as much as a month earlier, they may be out of priority for their water rights and may not be able to utilize all or some of their water rights as a result."

But Finnessey said there may be some water users who will benefit from this shift.

"In climate change there are winners and losers and there are folks that by having an earlier runoff may actually see an increase in the water that they're able to access because they will be more in priority and they'll be able to pull more water from the river and I think there are others that will be on the losing end."

Those senior water rights holders are often municipalities who have ample storage to capture that early runoff water. Kim Hutton, a water resources engineer with the City of Boulder said when snowpack starts to melt, the city starts filling its reservoirs.

"So how that works for Boulder, it actually may work to our benefit in that the water supply is available and based on our water rights, we're able to fill our reservoirs earlier in the season than we would be under today's conditions," she said.

As a fourth generation corn grower in La Salle Colorado, Dave Eckhardt has seen the changes in water resources in the state firsthand. That's why the president of the Colorado Corn Growers Association said the ability to store early season water is so crucial.

"I think it only brings to light the need for the ability to store more to retime the run off to keep water in the river," he said. "Keeping water in the river is about the only thing that is going to keep ag in the state."

Water storage itself is a complex issue. Some environmental groups have criticized plans for reservoir construction and expansion in the state citing its impact on ecosystems and river health – the long planned Northern Integrated Supply Project is an example. For climate and water researchers like Jeff Lukas, reservoirs in and of themselves are not a solution to climate change's impact on water resources.

"If stream flows not only shift in timing which we expect but also decline, which is a very real possibility, then some of the contemplated reservoirs may not be filled reliably and serve their purpose," Lukas said.

In other words, a reservoir is only useful if there's water to fill it. Climate change models predict not just earlier runoff, but drier and hotter conditions, leaving all water users scrambling for diminishing resources.

This story comes from ‘Connecting the Drops’ - a collaboration between Rocky Mountain Community Radio and the Colorado Foundation for Water Education. Find out more at cfwe.org.

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