Washington County to build a reservoir and park at Toquerville

Ash Creek project would improve existing water system, but is it really needed?

(Google Maps) This satellite image shows the area where a proposed reservoir and park could be developed in Washington County.

A new reservoir could soon be filling near Toquerville where Washington County water officials hope to create a park on federal land where they plan to capture water from Ash Creek, an important Virgin River tributary.

The $35 million project is intended to better utilize existing water infrastructure associated with Ash Creek — including a spring that produces millions of gallons of high-quality water that is largely used to water alfalfa — rather than develop new ones, according Zach Renstrom, general manager of the Washington County Water Conservancy District.

“It’s another location where we can store water during the spring runoff or wet years and we can capture that water and carried over into other areas that are drier,” Renstrom said. “There will be some groundwater recharge that will be occurring with this reservoir, into the Navajo sandstone that will be beneficial for those dry years.”

(Christopher Cherrington | The Salt Lake Tribune)

The proposed Toquer Reservoir would store up to 3,638 acre-feet in currently dry washes administered by Bureau of Land Management, which is conducting an environmental assessment for the project. The dam requires a right of way on BLM land for the inundated land and various pipelines. A final assessment and decision is expected later this year.

Just west of Toquerville on State Road 17, the 115-acre lake would be impounded behind a 100-foot high dam located off Ash Creek’s main stem. Water would get to it through a system of pipelines from the existing Ash Creek Reservoir, located upstream on Interstate 15.

The conservation community has been at odds with the water district over various water development projects, but the Ash Creek project has not generated much opposition.

“We don’t see any issues here,” said Tom Butine, president of Conserve Southwest Utah. “It doesn’t seem to be in any critical habitat. We have stayed mute on it. We would support improving the efficiency of our local water systems.”

The BLM is now taking public comment through June 1 on a related proposal to grant 11 acres to the water district for a lakeside park, which would include a primitive campground and boat ramp.

“It’s going to be a beautiful little lake. There’s going to be fishing on it,” Renstrom said. “Individuals can take out non-motorized boats on it, like kayaks or canoes. Around the lake there’s going to be a walking path. There’s going to be a couple of spots where people can go for picnics.”

Upstream from the proposed reservoir is Toquerville Springs, which discharges water at an average rate of 10 cubic feet per second, which translates into 7,239 acre-feet a year, about twice the capacity of the proposed reservoir. This water is so pure it can be used for drinking with minimal treatment, yet most of it is used to irrigate alfalfa, whose growers have held rights to this water for a century. The new reservoir would enable the water district to replace these farmers’ water with surface water so the fine spring water can all be used in homes.

That spring already has infrastructure for culinary,” Renstrom said. “The pipes are already there. We literally just have to turn a valve and direct more of that water to the culinary line.”

The project’s main purpose is to prevent the loss of about 1,740 acre-feet of water annually that seeps into the ground under Ash Creek Reservoir. That dam was built in the 1960s beside the freeway, impounding water over a basalt lava flow whose soils don’t contain water well, according to the BLM.

“The reason why that reservoir was put there was because of I-15. It wasn’t a good location for a reservoir. And so it has lots of problems with seepage. It dries up,” Renstrom said. “So we’re taking that water and bringing it down to an area that is better suited for a reservoir. And this will allow us to also do more groundwater recharge in that location where we need it.”

To avoid further losses in transit, the Ash Creek water would be piped through a 19-mile network of lines terminating in the new reservoir.

“As the water comes down from that location, it just seeps into the ground and we lose a lot of it. The geologists are saying that’s right along the Hurricane fault. So that water most likely hits the fault and just goes very deep into the ground and we lose it,” Renstrom said. “So we [will] capture it and bring it down in the most efficient manner and that’s with a pipeline.”

The district has already begun bonding to finance the project, according to Renstrom. Revenue to cover this debt would come from water rates, impact fees and property taxes. The district hopes to begin preliminary construction this year and construct the dam in the fall of 2022.