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Platte, but these are small compared to the required release from Lake McConaughy. <br />Shortages occur on individual days due to system capacity constraints. Shortages are <br />typically a result of: <br />• North Platte River capacity at North Platte - The modeled capacity of 3,000 cfs at <br />this location on the North Platte limits the release to the river from Lake <br />McConaughy. <br />• North Platte River below Keystone ramping limitation - this ramping rate <br />typically limits releases from Lake McConaughy when diversions at Keystone are <br />changed based on downstream limits or historical operations. <br />• Capacity and ramping rates of the Keystone Diversion, capacity in Sutherland <br />Canal, and capacity and ramping rates at the North Platte Hydro Return - the flow <br />diverted at the Keystone Diversion is influenced by the capacities and historical <br />flows at all three of these locations. On occasion, one, two, or all three can limit <br />the amount of Program water able to return to the South Platte River, <br />circumventing the choke point on the North Platte River. <br />These limitations to target flows vary from year to year and within the same year being <br />analyzed. <br />There are instances during the irrigation season of some years when flows in the river <br />exceed flood stage limits due to historical flows. The occurrence of these events near the <br />downstream end of the system are difficult to incorporate into the release determination <br />for achieving the 800 cfs target. These events are infrequent and do not appear to <br />represent a significant impact on the volume of EA water released. Refinement of this <br />capacity limitation will potentially be addressed in Phase II as part of routing tool <br />refinements. <br />4.0 PROJECT ASSESSMENT <br />The Platte River Water Conservation/Supply Study (Boyle, 1999) and Reconnaissance-Level <br />Water Action Plan (Boyle, 2000) provided supporting information for the Governance <br />Committee to select a package of thirteen alternatives to reduce average annual shortages to <br />B0VLE Page 38 of 58 January 29, 2008 <br />PRRIP - Draft Water Management Study, Phase I