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An engineering review of the CB Ranch water rights court case indicates the calculations filed by the Security Water District could be off by as much as a factor of three.

Chris Manera, PE, with Colorado River Engineering reported his findings at the Upper Arkansas Water Conservancy District’s January board of directors meeting.

Manera said the Div. 2 Water Court case involves a change of use for four water rights that were historically used for irrigating CB Ranch alfalfa fields along U.S. 50 in Coaldale.

The conservancy district filed a letter of opposition in the case to attain legal standing, and the district’s engineering and legal firms have analyzed Security’s filings to ensure the resulting court decree protects Upper Ark Valley water interests.

“Our calculations show a few differences from Security’s numbers,” Manera said. “The biggest difference is on return flows. In winter, they’re showing 30-acre-foot returns. We’re showing double to triple that.”

Return flows are the water that returns to the stream system after being used by the water right owner. In this case the CB Ranch diverted water from Hayden Creek to irrigate its alfalfa fields. Water not consumed by the alfalfa either evaporated or ended up in the Arkansas River as return flows.

For a water right change-of-use case, Colorado law requires that the change not injure other water rights owners.

Manera said the difference in return flows could potentially injure conservancy district water rights as well as the Winter Water Storage Program.

Upper Ark Director Tim Canterbury also questioned the accuracy of Security’s numbers based on observations during decades of ranching in Coaldale: “I think they are off.”