Carbondale’s Weaver Ditch focus of study on water efficiency

A project funded by Pitkin County aims to keep more water in the Crystal River by improving the efficiency of Carbondale’s Weaver Ditch.

The Weaver Ditch Existing Conditions Assessment will survey the roughly three miles of ditch that flow through downtown Carbondale from its diversion point at the headgate just west of state Highway 133 near South Crystal Bridge Drive to its confluence with the Roaring Fork River.

From the survey will come a detailed engineering plan to pinpoint where improvements could increase efficiency, delivery and use of the irrigation water. Four gauges will be installed in the ditch to help measure and understand the flow pattern.

The Weaver Ditch (also known as the Weaver and Leonhardy Ditch) is mostly used for raw water irrigation of Carbondale’s open space, parks, golf courses, schoolyards and residents’ yards. The Weaver Ditch runs through Carbondale and Sopris Park, and residents can use it to water their lawns and gardens for free.

Built over a century ago, the open (unpiped) and unlined Weaver Ditch could potentially be leaking water into the surrounding soil in some areas.

“Most of these ditches are pretty old, and the folks get in there and they clean them out and they do everything they can with them with the resources they have, but they were built and designed and created basically with the technology from the 19th century,” Ken Neubecker told the audience at a May 31 State of the River meeting in Carbondale.

Neubecker is associate director of the Colorado Basin Program for American Rivers and a Pitkin County Healthy Rivers and Streams board member.

Carbondale has three water rights that allow it to divert water from the Crystal River into the Weaver Ditch, a total decreed use of 12.36 cubic feet per second. The oldest of these rights dates back to 1885.

According to Carbondale Utilities Director Mark O’Meara, the town diverts on average about 3.5 cfs from the Weaver Ditch during the irrigation season and has not diverted its full decreed amount in quite some time.

Part of the reason, O’Meara said, is because there often isn’t enough water in the Crystal River, especially during the late summer irrigation season, for the town to divert its full decreed amount.

The survey is a collaboration between the town of Carbondale, the Roaring Fork Conservancy and American Rivers. Pitkin County commissioners approved $30,000 in funding for the project from the county’s Healthy Rivers and Streams Fund at a May 8 work session.

The survey has a total cost of $40,000 and work is slated to begin this fall once the ditch has been turned off for the season. The remaining $10,000 in funding will come from private donors, according to Heather Tattersall Lewin, watershed action director at the Roaring Fork Conservancy.

Besides leaving more water in the river, another goal of the project is to serve as an example for other upstream irrigators on the Crystal, especially those who might be reluctant to participate in a ditch survey.

“This is a pilot project within the town,” Neubecker said. “Hopefully it’s something that we will be able to expand with the other ditches in the town, the ranch irrigators and other people around the Crystal and Roaring Fork valleys and get this to work.”

Not having enough water in the lower Crystal River has been a concern in recent years. The 2012 drought left a section of the Crystal between Thompson Creek and the state fish hatchery dry during the late summer irrigation season.

Leaving more water in the lower Crystal River — an additional 10 to 25 cfs during times of moderate drought — is a goal of the 2016 Crystal River Management Plan. To accomplish this, the plan calls on the town of Carbondale to line its leaky irrigation ditches. It also suggests creating non-diversion agreements, or paying irrigators to reduce their diversions, and helping them improve ditches and install sprinkler systems.

According to the Crystal River Management Plan, converting an earthen ditch to a concrete ditch or pipeline conserves as much as 30 percent of diverted water because it reduces water loss to seepage and evaporation.

The Colorado Water Conservation Board holds a junior instream flow right of 100 cfs in summer and 60 cfs in winter, which is currently the only permanent mechanism in place to ensure there is water for ecological purposes. But during times of drought, the instream flow right is often not met due to the board’s junior status to most other diverters under Colorado water law.

The Weaver Ditch is downstream from where the worst dewatering takes place. But Lewin Tattersall hopes the Carbondale project will inspire upstream diverters to survey their own ditches.

“We know there are places upstream where efficiencies could be beneficial and having the town of Carbondale demonstrate that they bought into the process and be an example is great because anywhere on that lower Crystal River could use more water,” Tattersall Lewin said.

The Weaver Ditch also will see its headgate and diversion structure improved as part of the Crystal River Restoration and Weaver Ditch Efficiency Project. In March, the board approved $20,700 in funding for the project.

Currently, town staff adjusts the headgate manually, depending on demand, rainstorms and other factors. But the goal, O’Meara said, is for the system that opens and closes the headgate to eventually become telemetry-based and automated.

“It’s a demand-based system that can automatically make adjustments so that you aren’t wasting water,” O’Meara said. “We are constantly looking at areas where we can improve on the ditches.”

Ultimately, the Weaver Ditch survey is a first step toward addressing the potential of a future with less water. As climate change raises temperatures, that could mean longer growing seasons for crops and a greater demand for more water.

“Overall, the need for water is going to grow,” Neubecker said. “It’s going to come down to how efficiently can you use your water.”

Aspen Journalism is collaborating with The Aspen Times, the Glenwood Springs Post Independent, the Vail Daily and the Summit Daily News on the coverage of rivers and water. More at http://www.aspenjournalism.org.