Building dams to slow down the pace of floodwater could save lives and reduce the destruction of property. But, it might also deprive a farmer of irrigation water or even deliver more to neighbors with more senior water rights. It could cause conflicts with neighboring states that have entered into compacts with Colorado.
Dams, detention ponds and even debris basins meant to trap sediment while allowing water to flow freely in areas ravaged by wildfire could be subject to state water rights administration. That’s the opinion of officials at the Colorado Division of Water Resources.
“I think we’ve clearly articulated how we view the law and there are not any gaps from an administrative standpoint,” said State Engineer Dick Wolfe.
But districts formed to control stormwater are discussing whether state water law could block efforts to stem the worst effects of floods. And they’re looking at changing the law to give more weight to arguments to detain water.
The Urban Drainage and Flood Control District, which was formed to assist Denver metro area counties with stormwater protection, has asked the state to clarify its position on whether flood control would have priority in any instance. Meanwhile, the Fountain Creek Flood Control and Greenway District is preparing a series of conversations with water rights holders on the same topic.
“If we as a district are going to be successful, we have to become involved,” Executive Director Larry Small told the Fountain Creek board at its August meeting.
The state’s position is that detaining water in a regional project could injure junior water rights.
In 2011, the state explained that its policy of allowing 72-hour detention of floodwater applies only to single-site projects, rather than regional detention ponds, said Kevin Rein, deputy state engineer. The rule has often been invoked in flood control discussions and usually misinterpreted. The Fountain Creek district found out about this firsthand when it constructed a demonstration project along Fountain Creek in Pueblo behind the North Side Walmart. It was required to file a substitute water supply plan.
But there are no hard and fast rules governing flood detention.
“We do not find a legal basis to make an absolute finding that diversions of stormwater into regional water quality detention are allowable, nor do we find a basis to determine that such diversions would cause no injury,” Rein concluded in his letter to the Urban Drainage district.
Even the debris basins built by Colorado Springs after the Waldo Canyon Fire have the potential to run afoul of state water law, said Steve Witte, Division 2 engineer. “If they encounter groundwater, they have to be augmented with a SWSP,” Witte said. “If it’s in a normally dry stream, it may qualify as an erosion control dam, which if it holds less than 2 acre-feet of water is statutorily exempt.”
So far, the state has looked at about 30 of those structures in the Colorado Springs area.
Flood control is not impossible. One of the stated benefits of Pueblo Dam under the Fryingpan-Arkansas Project is to provide protection from floods. The operating rules of the dam allow holding back water if the Arkansas River is above 6,000 cubic feet per second at the Avondale gauge — a level that satisfies most water rights downstream.
However, Fountain Creek officials know they could have a tough time trying to unravel the water rights questions that will accompany any dam or detention pond project.
“It’s going to be a tough fight, but the best way is to confront it,” said Pueblo County Commissioner Terry Hart. “We have to put an effort together to try to negotiate it up front. The only way to identify the issues is to speak to those who might be hurt downstream.”