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Future Condition - Additional Ground-water Development An analysis was also made which simul ates the effects of additional ground-water development in Nebraska. This future condition includes the operation of Grayrocks Reservoir and the 1977 present condition flows below Guernsey and at Julesburg. Table 14 presents the estimated monthly flow conditions. Growth of irrigated agriculture would occur in Nebraska under this con- dition due to continued ground-water development. This has a signifi- cant depletionary effect on surface flows in Nebraska. The finite difference model developed to simulate the approximate effects of present ground-water irrigation development on the flows of the Pl atte River in Nebraska was also used to simul ate flow conditions that may be expected to occur with additional ground-water development. Under the future condition it is assumed that all of the irrigable 1 and having access to a ground-water supply would be developed over the next 50 years. This would indicate that a total of 3.2 million acres could be irrigated from ground-water suppl ies with a net pumpage of 2.6 mi II ion acre-feet per year. Therefore, there woul d be an increase of 1. 8 mi 11 ion acres wh i ch woul d be added to the present i rri gated acreage at a rate of 2 percent per year. Results indicate that streamflow depletions would be 568,000 acre-feet per year, or 384,000 acre-feet per year greater than at present. Ground-water storage ,woul d be depl eted at a rate of 1. 9 mill ion acre- feet per year. In addition, some 357,000 acres of subirrigated land would be lost, resulting in the salvage of 473,000 acre-feet of water per year. Using the Platte River at Overton as an example, the annual flows are reduced by about 20 percent of the flows depicted in the future condition without additional ground-water development. At Grand Island, the reduction is 25 percent. 54