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3.4 Update of WMC Loss Model Spreadsheet <br />The original Water Management Committee (WMC) water budget spreadsheet model <br />(loss model) spanned 20 water years from 1975 through 1994. The loss model was <br />expanded to include hydrology for water years 1995 through 2006 to provide a <br />comprehensive analysis by including the driest drought years of 2002 through 2006. <br />A technical memorandum is included in Appendix 2, providing a detailed explanation <br />of modifications and assumptions made. <br />3.5 Travel Times and Daily Losses <br />The geographic separation of Lake McConaughy and Overton, Nebraska, the natural <br />and constructed environment, and variability in hydrology all contribute to the <br />complexity of estimating the timing and magnitude of a timed release of Program <br />water necessary to meet target flows downstream at the Critical Habitat. These <br />complexities are approximated with the use of travel times and loss factors <br />incorporated into spreadsheet calculations. Empirical estimates for these variables <br />were derived based on analysis of daily streamflow and diversion data for specific <br />river reaches and information gathered from the participant interviews. <br />Travel times were estimated for the river and canal systems from Lake McConaughy <br />on the North Platte River and the Roscoe gage on the South Platte River, downstream <br />to the Overton gage on the Platte River. Intermediate locations include North Platte, <br />NE (the confluence) and the Brady gage. These intermediate locations were chosen <br />based on the location of stream gages, and relative proximity to the Districts' <br />diversions and returns. The confluence of the North and South Platte Rivers, the <br />North Platte Hydro Return, and the CNPPID diversion are grouped together for <br />purposes of estimating travel time. Travel times were rounded to daily increments due <br />to the daily time step of the routing tool. Based on discussions with the Districts' <br />staff, travel times for the canals are estimated to be the same as travel time in the <br />coincident river reach. <br />B042E Page 17 of 58 January 29, Zoos <br />PRRIP - Draft Water Management Study, Phase I