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• <br />It was assumed that scenarios 1 through 3 involve pumping to a drain <br />that will deliver water to the river. There are numerous drains <br />throughout the area impacted by the mound that intercept groundwater <br />and return to the river. The intent of these scenarios is to minimize <br />costs and use these drains to return water to the river to the maximum <br />extent possible. There could be opportunities to route groundwater <br />pumped from the mound through wetlands and wet meadows along the <br />Central Platte, however, this has not been considered in this analysis. <br />Scenarios 4 and 5 assumed water is pumped directly to canals and <br />laterals that currently serve the irrigated lands under E -65, E -67, and <br />Phelps County Canals. <br />These scenarios apply to the downstream end of Reach 10, Reaches 17 <br />and 18, and the upstream end of Reach 19. Scenario 1 is a project that <br />has the potential to reduce groundwater exports from the basin, <br />whereas, Scenarios 2 through 5 target returns flows contributing to the <br />growth of the mound. Scenarios 1, 2 and 3 are essentially the same in <br />concept and involve pumping from the mound up to 51,000 ac- ft/yr, <br />36,500 ac- ft/yr, and 14,500 ac -ft/yr, respectively, as shown in Tables <br />8.G.42 through 8.G.53. For scenarios 4 and 5, it was assumed that <br />14,500 ac -ft and 51,000 ac -ft, respectively, of the annual irrigation <br />supply for lands irrigated under the E -65, E -67, and Phelps County <br />Canals could be supplied by groundwater as opposed to surface water. <br />The monthly distribution of pumping is based on the average monthly <br />distribution of surface water diversions for the E -65, E -67, and Phelps <br />County Canals. Reducing the supply in the irrigation system by 20 cfs <br />to 70 cfs would not be great enough to change the operations at Lake <br />McConaughy. Demand changes of up to 70 cfs would be small in <br />relation to the total demand for Lake McConaughy storage releases. If <br />surface water is saved in the irrigated area due to conversion to <br />groundwater irrigation, it was assumed that returns to the Platte River <br />though the J -2 return would increase by a similar amount. Therefore, <br />this water would reduce the need for EA releases in the summer and <br />would have minimal impact on Lake McConaughy operations. The net <br />hydrologic effects of scenarios 4 and 5 are shown in Tables 8.G.54 <br />through 8.G.59. <br />Maps of the build -up in the water table were reviewed to determine <br />whether effective well sites exist in each reach. The most effective <br />sites for these projects are located in Reaches 10, 17, 18, and 19 where <br />the mound build -up is most prominent. Pumping from the mound in <br />Reaches 10, 17, 18, and 19 applies to about 20 miles, 28 miles, 16 <br />8 -G -58 <br />