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• Incremental changes in gains and losses between Overton and Grand Island are <br />negligible. <br />• Rainfall falling on water surfaces was assumed to be added to the reservoir volume <br />in full. Historical daily precipitation data was obtained from the Holdrege weather <br />station. <br />• Runoff contributed from rainfall falling on the drainage basin surrounding the <br />reservoirs was subject to SCS losses. Antecedent moisture conditions were used. <br />0 Seepage through the dams was estimated using Darcy's Law and the geometry of <br />the dam along with soil characteristics. Daily seepage rates were based on the <br />water surface elevation at the beginning of the day. <br />• Evaporation was based on available climate data for the North Platte weather <br />station. A constant water surface area associated with one -half the reservoir depth <br />was used for each reservoir for the purpose of determining evaporative losses and <br />direct rainfall. <br />• The reservoirs began the study period empty. <br />• Inflow and outflow capacities were preliminarily set by conversations with <br />CNPPID. Fill capacities ranged from 100 to 400 cfs, while release capacities were <br />set at 50 cfs for all reservoirs. Changes to these capacities will affect yield results. <br />• No freeboard was used in the hydraulic and hydrologic analyses. Water was <br />considered to be spilled in full beyond the normal volume of the reservoir. <br />Water was available in the Canal up to the amount of the historic J -2 Return during <br />periods when diversions into the reservoirs were made. The water diverted from <br />the Canal to be stored in the reservoir could not exceed the flow in the J -2 Return. <br />Daily reservoir operations data, including diversions to storage and releases, have not yet <br />been made available by HDR and CNPPID. <br />0 Legal And Institutional Requirements for Implementation: <br />There may be several legal and institutional requirements necessary to implement any of <br />these reservoirs. As noted by NPPD in comments received May 3, 2000, the operational <br />rules must insure that all senior water right demands are met before storage is considered <br />or credited to a CNPPID re- regulating reservoir. This condition should be met if water is <br />only available for storage on days that flows downstream of the J -2 Return exceed the <br />needs of existing water rights. <br />Nebraska will also explore several institutional alternatives for capturing, releasing, and <br />protecting water generated from a re- regulating reservoir if it moves forward (Nebraska's <br />Comments on Boyle January 17, 2000 Memo). Potential institutional alternatives <br />presented by CNPPID, which address legal requirements, are as follows. If the reservoir <br />\\DN00 \E- DRIVE \PROJECTS\Platte \Work Products \Task 9 \wapc report (Version 7).doc 11 <br />