Cook Evaluation of Wyoming's New Depletions Plan

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an offset for the subbasin 1 overrun. However, there is no reason to route the subbasin 2 under run downstream as it cannot be used as an offset for any overrun in Baseline 2. Only the net Baseline 1 averrun should be routed as described above. Baseline 1, Overruns Below Pathfinder Assumptions: • Overruns in this area could result from either or both of the following: (1) an above average water supply above Pathfinder that gets passed through because of natural flow demand or because Pathfinder is spilling or (2) an above average water supply on the tributaries downstream of Pathfinder. Either way, an overrun in this area will reduce the amount crossing the state line that year or, unless supplies are so good that storage water is not needed, will reduce the amount of natural flow and increase the amount of storage water used by North Platte contractors that year. As per the Wyoming NDP, an under run in use below Guernsey (including the Laramie subbasin) cannot be used to offset an overrun in this subbasin because the below Guernsey subbasin is in Baseline 2. As with overruns above Pathfinder, Wyoming will want to offset them as soon as possible rather than let them accumulate. Allowing annual offsets would cause no significant harm to Nebraska or to the Program as long as the offset water crosses the state line at the same locations and in approximately the same proportions as would have crossed at those locations in the absence of the overrun. Conclusions: • An overrun in this area can be offset by an under run in the subbasin above Pathfinder (subbasin 1) even though the overrun likely will not result from that under run. • The practical effect of most overruns in subbasin 2 will be the same as for those in subbasin 1. That will be to cause a reduction in the future water supply for North Platte contractors in either Wyoming or Nebraska. • Any net overrun in Baseline 1 should be offset at or above Whalen. Offsetting at Whalen will cause such offsets to cross the state line at the three crossing points in proportion to the reductions in flow at those points that are caused by the net overrun. • For purposes of routing, the amount that does not reach Whalen because of any net overrun in Baseline 1 caused by excess use in subbasin 2 should be reduced only by the storage conveyance losses from Pathfinder to Whalen. • Wyoming should be allowed to offset the net overrun, after routing, at Whalen on a year by year basis even though the impacts would have otherwise likely not been experienced until the first allocation year thereafter. Baseline 2 Baseline 2, Under Runs In All Subbasins Assumptions: 3