From The Sterling Journal-Advocate (Jeff Rice):
Brad Wind, general manager of the Northern Colorado Water Conservancy District based in Berthoud, and Jim Hall, Northern Water’s senior water resources engineer, briefed the LSPWCD’s board of directors on Northern’s efforts to keep Colorado-Big Thompson water from leaving the Northern District…
Wind told the Lower board that Northern is working to enforce Article 19 of the 1938 contract between Northern Water and the federal government, known as the Project Repayment Contract. That article, one of 27 contained in the contract, specifies that all seepage and return flows from the use of Colorado-Big Thompson project water are reserved to Northern Water and are not to be taken outside the district’s boundaries.
On May 9, Northern adopted a resolution saying it would “take appropriate actions to enforce Article 19 consistent its interpretation of Article 19.”
Wind said the heavy lifting in that effort will be tracking how C-BT water, and resulting seepage and return flow, are used. He used the phrase “colors of water,” which is a concept that holds that, through close monitoring and accounting, mixed waters from various sources actually can be tracked through multiple uses. For instance, water that is native to the South Platte Basin can be accounted differently from C-BT water, which is diverted from the Colorado River into Grand Lake and piped through the Adams Tunnel to Estes Park and held in Horsetooth Reservoir and Carter Lake for distribution to C-BT members.
Return flows are water that has been diverted from the river, used to irrigate crops or for municipal use, and either seeps back to the river through the ground or is discharged after treatment. Much of the river’s flow in the lower reaches in late summer and through the winter is from return flows from upstream use. Return flows are crucial to irrigators in Weld, Morgan, Washington, Logan and Sedgwick counties.
“To protect return flows, we have to know what they are,” Wind said. “We have to be able to quantify what return flows are coming from C-BT use and what’s from native water. It’s complicated.”
Hall told the Lower board that there is the danger that “change of use” cases going through Colorado water courts could result in return flows from C-BT water being shipped out of the Northern district in violation of Article 19.
“We’re starting to see change cases on irrigation ditches moving water outside the district boundaries,” Hall said. “That’s why it’s important to track this stuff. It’s easier to track municipal water because we can look at their (wastewater treatment facility) discharges, but it’s harder to prove agricultural return flows.”
Hall said return flows from native water are not subject to Article 19, only C-BT return flows.
Wind said Northern will be watching closely all change of use cases that go through Colorado’s water courts and will continue monitoring water usage in the district to make sure C-BT water doesn’t leave the district.