During the October storms in southern Utah, the Virgin River was rushing at about 10,000 cubic feet per second at the Quail Creek Diversion Dam, according to the Washington County Water Conservancy District. When the river is not flooding, it moves at about 100.
That is roughly a hundred times its normal flow. And as KUTV reported, the water did not come alone.
"There's so much debris and sticks on top of the water that you can just about walk across it," said David Jessop, operations manager for the district.
Why Most of the Floodwater Stayed Out
The district says large amounts of that floodwater cannot go into its drinking water reservoirs. It moves too fast, there is too much of it at once, and the quality is poor. Along with the debris, it carries thick mud.
Jessop said the debris needs time to settle out. If it does not get that time, it clogs the intakes and makes for rough conditions in the pipeline.
Some of the water still made it in. Quail Creek, one of the district's main drinking water reservoirs, rose 5 1/2 feet over a few weeks.
Screens at the Intake
The district has added rotating trash screens that clean themselves of debris and let more water into the pipeline. Jessop said it would still take major infrastructure work in the future to take in all of the water.
The reason for those screens is simple. Whatever the water carries, somebody has to keep it out of the system.
Every Gallon Counts in Southern Utah
Spring runoff supplies most of the water in the district's drinking water reservoirs, Jessop said. Floodwater that soaked into the soil this fall should help when the snow melts, because more of the runoff will reach the river instead of the ground.
St. George resident Constance Thomson told KUTV that rapid population growth has people thinking hard about whether there will be enough water to go around.
In a place where every gallon is counted, what goes into a reservoir matters as much as how much.
What Settles to the Bottom
Debris on the surface of a flooded river is easy to see. Debris that reaches a lake or reservoir and sinks is not. Sticks and leaves break down over time. Much of what people leave behind does not.
The largest of it is vehicles. A submerged vehicle carries a fuel tank, engine oil, ethylene glycol and a lead acid battery into the water. Under the Clean Water Act, a discharge that leaves a visible sheen on the water is reportable. Our Utah Waterways Submerged Debris Atlas documents an estimated 499 submerged items across 20 Utah lakes, including 56 vehicles and 103 vessels that are individually confirmed.
What We Do Now, and What We Are Building
Fathom Restoration is a disabled-veteran-led Utah 501(c)(3) nonprofit. Today our volunteer divers carry trash out of Utah's lakes and reservoirs by hand. Since September we have logged volunteer dive cleanups at Deer Creek, Sand Hollow and Strawberry, about 93 pounds of trash by our estimate across 63 volunteer hours.
The vehicles will take far more than hands. We are working to start recovering submerged vehicles, and we are doing it in order: insurance, permits and commercial dive certification first.
Below the Screens
A water district in southern Utah built screens to keep debris out of its pipes. The lakes and reservoirs across the state need the same attention below the surface, where nobody sees what has settled. That is the work we are here to do.
Fathom Restoration is a disabled-veteran-led Utah 501(c)(3) nonprofit running volunteer dive cleanups on Utah's lakes and waterways and building toward the recovery of submerged vehicles and vessels. Donate or volunteer at fathomrestoration.org.
Source: https://kutv.com/news/local/debris-speed-make-stormwater-unusable-for-drinking-water-reservoirs
