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Option 6: J-2 Forebay Reservoir. This site is located southeast of Lexington in Gosper County in the Plum Creek basin, south of the J-2 Forebay on the south side of the Canal. This reservoir would be gravity fed fromthe Supply Canal. The reservoir capacity is estimated to be 3,436 ac-ft, o Basic Description: Re-regulating reservoirs capture Platte River water beyond that required for irrigation deliveries and mainstem instream flows during periods of excess flows at the critical habitat. In general, water would be diverted from the Central District Supply Canal during periods of excess and released during periods of shortage at the critical habitat. In the case of the Jeffrey Canyon and the J-2 Forebay Reservoirs water would be supplied from Jeffrey Reservoir and J-2 Forebay, respectively, as opposed to the Canal. CNPPID is proposing to re-regulate flows in their system, in which case diversions will not be increased or decreased, only return flows will change. o On-Site Hydrologic Effects: The HDR Report was relied on for yield estimates. Nebraska is reserving 50 percent of the yield to offset future depletions, in which case only 50 percent of the yield is available to the Program. The on-site yields presented have not been discounted, therefore, the EIS team will need to consider the reservation of water for Nebraska's offset purposes in determining the scores associated with these reservoirs, HDR developed a spreadsheet to analyze the flow regime of each potential reservoir. Reservoir operations were modeled on a daily basis, Daily operation is possible due to the close proximity of the reservoir to the habitat. Days of excess can occur in months that the monthly flow does not exceed monthly target flows, in which case, the reservoir could be operated to store on days of excess and release on days of shortage. These reservoirs can take advantage of short-term excesses and shortages in a more efficient manner than other alternati ves that are further upstream. The following assumptions and operating rules were used by HDR to determine the yield and timing associated with these reservoirs, . No dead pool was accounted for. All reservoirs were allowed to drop until they were dry, · Type of year for purposes of defining target flows (wet, average, or dry) is known. · Travel time from Overton to Grand Island is two days, Historic flows at Overton were used to determine the amount of water that should be stored or released from the reservoirs to meet the target flows at Grand Island. C:\Draft Waler Action Plnn (MllY 30, 2()(x))\wnpc repOlt (Version 6 BNOO)-.doc II