Water Conservation / Supply Reconaissance Study Part 2

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�11 • • miles, and 16 miles of the Platte River, respectively. It was assumed that a high capacity well could be located every quarter mile along the length of the river in the vicinity of the mound. Irrigation wells in Central Platte area south of the Platte River typically average 1,000 gpm. Based on these factors, monthly groundwater pumping in Reaches 10, 17, 18, and 19 was limited to 10,500 ac -ft, 15,000 ac -ft, 8,500 ac -ft, and 8,500 ac -ft, respectively. The monthly limits on groundwater pumping are constrained by the number of wells and the average pumping rate. These limits do not apply to scenarios 4 and 5 because wells can be located throughout the irrigated area under Phelps County, E -65 and E -67 canals. For all scenarios, it was assumed that pumping occurs only during periods of target flow shortages. The net effect on the river is assumed to be the amount pumped returned to the river in that month because wells are assumed to be pumping water that would have been contributing to the growth of the mound and/or into the Republican and Little Blue River Basins. The groundwater mound is in connection with the Platte River and contributes directly to providing return flow gains to the central Platte River, therefore, pumping from the mound could reduce flows to the river. Alternatives were assumed to be located further from the river to increase the likelihood that the majority of the water pumped is from the mound growth and transbasin exports rather than Platte River return flows. Based on this assumption the reductions to Platte River flows from pumping the mound were assumed to be negligible. However, site specific studies would be required to estimate the amounts of water pumped from each source under these scenarios and to account for reductions in Platte River return flows. The yields associated with these projects would decrease if a portion of the water being pumped consists of Platte River return flows. The water budget spreadsheet was used to route additional flows associated with each scenario downstream to the critical habitat to determine potential reductions to target flow shortages. Two routing scenarios were evaluated for the proposed recharge project. The first scenario assumes additional flows can be protected from downstream diversions, in which case, additional flows are not reduced by diversions. The second scenario assumes additional flows cannot be protected from downstream diversions, in which case additional flows are reduced by diversions. Reductions to target flow shortages without diversion losses are shown in Tables 8.G.60 through 8.G.77. Tables of 8 -G -67