Study: Not enough water for instream flow

by Cat Urbigkit

There is simply not enough unappropriated storage or direct flow water to fulfill the Wyoming Game and Fish Department's (WG&F) request for a year-round instream flow in Pine Creek of 40 cubic feet per second (cfs).

That's the conclusion of a feasibility report prepared for the Wyoming Water Development Commission by contractor Rio Verde Engineering of Pinedale.

State law mandates that a hydrological study be performed for all instream flow applications.

WG&F has filed two applications with the State Engineer's Office (SEO) for an instream flow. One application, called a "secondary application," seeks to use the 952 acre-feet of WG&F stored water for an instream flow, as well as use the 4,800 acre-feet the Town of Pinedale has agreed to lease to the state wildlife agency.

If approved, the secondary application would be Wyoming's first instream flow right that uses stored water. Although the state instream flow law allows such an action, to date it has never been done.

The second application before the SEO is WG&F's application for a direct-flow water right for an instream flow for Pine Creek. The application states: "As provided by (state statute), natural direct flows up to 40 cfs are requested whenever they are naturally available at all times during the year to improve the fishery in Pine Creek. This water right will function in tandem with secondary water rights owned by WG&F and the Town of Pinedale in Fremont Lake for instream flow purposes."

A public hearing on the WG&F instream flow application is scheduled for Dec. 19 at 9 a.m. at the Sublette County Library in Pinedale.

Because the flows are so different in various segments of the nearly eight-mile stretch of creek that WG&F has proposed receive an instream flow, Rio Verde divided the creek into three reaches for analysis. The first reach is from the Fremont Lake outlet to Willow Island. The second is from Willow Island to about a mile south of the Town of Pinedale (near the sewage ponds). The third reach continues to the confluence with the West Fork New Fork River.

First Rio Verde performed an analysis on unappropriated direct flows for each stream reach. The company reported: "There is not enough excess water in the system during high flow months to fill additional storage to satisfy the requested flows. The months that do show surplus water are due to return flows that occur downstream at a point in the system where the surplus water cannot be feasibly stored and released for instream flow."

Rio Verde concluded: "The mean monthly flow analysis indicated that the instream flow requests are not met in any of the months in Reach 1 and are only met during October in Reach 2. Requests are not met on an average year for the months of October and November in Reach 3."

In addition: "Reach 1 is fully appropriated for all months of the year during an average year. There are some unappropriated flows in the lower two reaches as a result of return flow, primarily from in-basin irrigation and the hydropower water rights discharge."

Next Rio Verde conducted a secondary storage analysis and determined: "The instream flow requests cannot be met using the secondary storage accounts alone. By distributing all of the storage evenly throughout the year, a minimum of eight cfs can be obtained for all months."

Rio Verde also examined the feasibility of combining secondary storage and unappropriated direct flows to meet the instream flow called for in WG&F's application.

The report concluded: "The instream flow requests cannot be met for all months using both unappropriated flow and secondary storage accounts as sources for instream flow. By effectively distributing the storage based on the available unappropriated direct flow for a particular month, a substantial instream flow can be legally delivered to the stream.

"Reach 1 has no unappropriated direct flow and consequently the only instream flow for that reach is what comes from storage. By distributing that storage evenly throughout the year, eight cfs can be obtained. On an average year, a minimum of approximately 14.7 cfs for instream flow can be obtained in Reach 2 and a minimum of approximately 23.6 cfs for instream flow can be obtained in Reach 3."