State looks to better measure water diversions — The #GrandJunction Daily Sentinel

Ralph Parshall squats next to the flume he designed at the Bellevue Hydrology Lab using water from the Cache la Poudre River. 1946. Photo Credit: Water Resource Archive, Colorado State University, via Legacy Water News.

From The Grand Junction Daily Sentinel (Dennis Webb):

Responding to challenges posed by drought, greater demand from a growing population and potential interstate Colorado River compact issues, a state water agency is looking to phase in rules in western Colorado that would require the use of measurement devices when exercising surface and groundwater rights.

State law already requires that owners of irrigation ditches and reservoirs install headgates with measurement devices where necessary, but while the Division of Water Resources can order installation of measurement devices, it never has adopted surface water measurement rules.

Groundwater measurement rules already are in place in several river basins east of the Continental Divide, in some cases as a result of court orders.

“Those have been largely in response to the need to administer groundwater rights within our (seniority-based) prior appropriations system along with surface water rights,” said State Engineer Kevin Rein, director of the Division of Water Resources.

He said surface water in basins such as the South Platte, Rio Grande and Arkansas also long has been overappropriated in terms of water rights, and water rights holders are accustomed to measuring their diversions closely, so surface water measurement rules in those places are not an immediate concern of the state, unlike the Western Slope…

[Mike Sullivan] said that in areas of high demand, many structures already have adequate controls and measurement devices, but some may need repairs to work properly, which is something the new rules can address.

Sullivan said growth in the state and more frequent drought years are contributing to calls for administration of water by DWR under the priority system and helping drive the consideration of the measurement rules…

The division sees measurement as important should Colorado ever face curtailment of water uses under a 1922 interstate compact if it and other Upper Basin states are no longer able to meet a compact provision regarding the amount of river water that flows to Lower Basin states on a 10-year average.

[Kevin] Rein thinks an Upper Basin failure to comply with that provision isn’t likely to happen until at least 2026, and says it’s easy to oversimplify the compact’s possible resulting ramifications.

But he thinks measurement would be important to determine how much water Colorado has been using and how much water would be taken from it in the case of curtailment.

The Division of Water Resources plans to make all the data gathered through measurement publicly available, as it involves diversions of what are waters of the state, administered through a system involving ownership not of water but of water rights…

Scott Hummer, water commissioner for District 58 in the Yampa River basin, checks out a recently installed Parshall flume on an irrigation ditch in this August 2020 photo. Compliance with measuring device requirements has been moving more slowly than state engineers would like.

The Division of Water Resources is looking to phase in new rules on the West Slope region by region, likely starting with the Yampa/White/North Platte river basins, DRW’S Division 6…

Rein said DWR may want to successfully work through rulemakings in a couple of its divisions between getting to Division 5, which covers the Colorado River Basin, as the basin is so large, with a lot of water volume and diversion points.

He thinks that Division 5 and Division 4, covering the Gunnison River Basin, have a lot more measurement devices than elsewhere in western Colorado, but said the devices aren’t as prevalent in some of the Colorado and Gunnison sub-basins.

Surface water measurement can be done using systems such as flumes, weirs, radar and current meters, while groundwater use is measured with meters or other devices. State officials say they don’t plan to impose one-size-fits-all rules.

They will takeinto account things such as the size of a diversion and a desire to require devices no more costly than what is needed to properly measure a diversion.

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