RAWLINS - A group of Upper North Platte Valley irrigators wants Wyoming officials to dismiss a petition from the federal government to change the use of 53,493 acre feet of water annually from Pathfinder Reservoir in part to help endangered species in Nebraska.

A hearing on the group's motion to dismiss the petition is set for Monday in Casper. It's scheduled for 9 a.m. at the Agricultural Resource and Learning Center at 2011 Fairgrounds Road.

Rawlins attorney John MacPherson filed the motion to dismiss the petition on May 23. He represents the Upper North Plate Valley Water Users Association and the Upper North Platte Valley Water Conservation Association, both based in Saratoga.

At the same time, MacPherson filed a motion for a change of venue for a scheduled Oct. 9 Board of Control hearing on the Pathfinder issue. He said if the Board of Control doesn't dismiss the BuRec's petition, his clients want the October hearing moved to Saratoga because many landowners who filed for party status in the matter live in or near Saratoga. It's now scheduled in Casper.

MacPherson and Fritz Holleman, a Boulder, Colo., attorney hired by the two water groups, plan to be in Casper Monday morning to argue the motions. An attorney from the Wyoming attorney general's office will represent the government, according to Allan Cunningham, administrator of the Board of Control division of the state engineer's office.

Cunningham said he couldn't comment on the board's position on the motion to dismiss the petition.

Calls to the BuRec's Mills office seeking comment on the Pathfinder modification petition and the hearing were not returned.

The motion to dismiss stems from a January filing by the BuRec seeking a change in use of 53,493 acre feet of Pathfinder's water and asking that water be assigned a senior 1904 water right. It's part of a massive water agreement among the federal government and Wyoming, Colorado and Nebraska to provide habitat for several endangered species in the Platte River in Nebraska.

Part of the deal is an agreement to expand the capacity of Pathfinder to provide more water for downstream uses.

The federal petition seeks a dedication of 33,493 acre feet of water for fish and wildlife purposes in Nebraska and asks that the other 20,000 acre feet be changed to municipal uses that would be made available to the state of Wyoming and leased to Wyoming cities and towns. It contends the change in use "will not affect the existing authorized uses of irrigation and domestic" in place for Pathfinder's water.

But, in the motion to dismiss, MacPherson says because Pathfinder was permitted for irrigation and domestic use, changing the use of some of the reservoir's water for wildlife purposes violates Wyoming law.

The motion to dismiss also questions the BuRec's request that a senior 1904 priority be assigned the new water uses.

The motion quotes a Wyoming Water Development Commission report that states, "Developing a new supply from in-basin sources under a current day priority would be virtually impossible."

MacPherson wrote, "To its credit, (the WWDC) is candid about why it has not requested a junior priority date." But he counters that is not a basis to award the new uses a 1904 priority.

"There is no precedent in Wyoming or anywhere else allowing a reservoir expansion to fill under the priority of the original senior right," the motion states. "The water users' simple and compelling position is that (the BuRec) cannot impose an additional 54,000 acre feet of senior demand in an already overappropriated basin without serious impacts to all upstream water rights.

"Allowing the proposed new space to store water for new purposes of use, to be made in new places of use, while filling under a senior 1904 priority, would turn the prior appropriation doctrine that is the basis for Wyoming water law on its head."

The motion also argues Board of Control regulations prohibit the change in use of the 53,493 acre feet because the change would harm other appropriators and the change would transfer more water than has historically been used.

And the motion disputes the BuRec's position that modifying Pathfinder would recapture space that's been lost to sedimentation. At least 25,000 acre feet that the government wants to revive has not been available for storage or subsequent beneficial use for at least 63 years, MacPherson wrote, citing the 1945 Supreme Court decision in Nebraska vs. Wyoming, which identified the capacity of Pathfinder then as 1,045,000 acre feet. When Pathfinder was built, it was designed to hold 1,070,000 acre feet of water.

MacPherson further argues that the petition should be dismissed because the government has failed to meet other Board of Control requirements, including providing proof of ownership or consent from all the landowners with affected water rights and a statement that the "appropriation to be changed is presently being applied to beneficial use."

MacPherson's motion suggests the BuRec instead amend its petition to request a junior priority date for the 53,493 acre feet, supply the information required by state laws and Board of Control rules, "and move forward from that point. That is how water rights for expanded reservoirs have always been handled in Wyoming. That is what should be done in this instance."