Summit County Citizens Voice

Colorado River Basin studies will help determine whether there is enough water for new reservoirs, and may also affect how Dillon Reservoir is managed in the future. PHOTO BY BOB BERWYN.

State experts try to determine how much water is left for future development and consumptive use, and climate change plays a big role in their calculations

By Bob Berwyn

SUMMIT COUNTY — After conducting what they say is one of the most rigorous studies ever of the Colorado River Basin, state officials concluded there may be some additional water available for development and use — or there may not, depending on what numbers are plugged into the computer models.

One of the models suggested there could be as much as 900,000 acre-feet of water in the Colorado River Basin available for consumptive use under the terms of the Colorado River Compact. Consumptive use permanently removes water from a watershed. Agricultural activities, irrigation and industrial cooling operations are examples of consumptive uses. However another model suggested that, if climate impacts are more severe, Colorado may have no water left to develop.

The amount of water available for future development is hotly debated as part of the planning for new reservoirs, diversions and other projects like pumpbacks of Blue River water in Summit County. The amount is also critical in the context of how Colorado River water is divided between the Upper Basin states (Colorado, Wyoming, Utah, New Mexico and part of Arizona) and the Lower Basin (Nevada, California and the rest of Arizona) states. The issue is critical for Summit County. If more reservoirs and pipelines are developed under the assumption that there is “extra” water in the Colorado River Basin, the county could be in for a rude awakening 30 years from now. In a drought scenario, with Colorado River water completely allocated, it’s conceivable that users with water rights from 1922 onward could face shut-offs if downstream states claim their full share, said Jim Pokrandt, spokesman for the Colorado River Water Conservation District.

“It addresses the amount of water that could be developed and consumed. The whole idea is to try and determine the risk of big projects,” Pokrandt said.

“Is there room for the big one? Will the water be there?” Pokrandt said, naming a proposed pipeline from Flaming Gorge Reservoir to the Front Range of Colorado as an example of the type of project whose fate could hinge on the final results of the study. Another example is the so-called Big Straw pumpback, a back-burnered project that would deliver “unused” Colorado River water from the Utah state line back upstream.

Current proposals for major new water projects may be proceeding under out-dated assumptions of how much water there really is in the Colorado River Basin, especially given the uncertainties of climate change impacts. Most projected climate change scenarios suggest significant changes to the hydrology of the Colorado River Basin, first and foremost with less predictable precipitation and runoff patterns.

“The Colorado River is one of the most important sources of water supply for the state,” said Jennifer Gimbel, director of the CWCB. “Colorado needs solid information in order to make smart decisions about future water development. This is probably the most rigorous assessment that has ever been completed of future water supply in the Colorado River basin and it’s telling us we still have a lot more to learn.”

“The Colorado River is one of the most important sources of water supply for the state,” said Jennifer Gimbel, director of the CWCB. “Colorado needs solid information in order to make smart decisions about future water development. This is probably the most rigorous assessment that has ever been completed of future water supply in the Colorado River basin and it’s telling us we still have a lot more to learn.”

The study looked at hydrology, water rights and current water uses in all four West Slope Colorado River basins, then used five separate climate change models to predict the probable physical water supply in the streams in the year 2040. Another element of the Phase I study examined a baseline of 1,100 measuring stations and tried to predict how climate change could affect individual streams. These modeling runs showed a general trend of earlier run-off and less water available than in the past.

Future Phase II work will get down to an even more detailed level to assess remaining water availability for future levels of municipal, industrial, agricultural, recreational, and other in-stream water needs. Additional information on the Colorado River Water Availability Study is available on the CWCB web site: http://cwcb.state.co.us/WaterInfo/CRWAS/.