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... ,. "fiR", .- ..~- 002484 DeDletioo Accouotiol! Water depletions are defined herein simply as diversions less return flows. Diversions include water diverted from the river, as well as evaporation from reservoirs and other impoundments, such as stock ponds. Depletions represent an annual reduction in the volume of stream flow that would have reached the critical habitat of the endangered fishes. Normal water losses due to direct evaporation from streams and rivers, transpiration by riparian vegetation, percolation to groundwater and bank storage are not considered depletions, as these also are characteristic of unmodified river systems. Current average annual depletions from the Yarnpa River in Colorado have been estimated using the CRDSS to be about 125,000 AF/year, while comparable depletions from the Little Snake River in Wyoming are estimated to be about 43,000 AF/year. Based 'upon projections of human water demands, depletion increments of 30,000 AF/year in Colorado and 23,000 AF/year in Wyoming were added to current depletions to account for anticipated water consumption circa 2045. Ranges of annual depletions, if normally distributed, would exceed projected average annual depletions of about 155,000 AF in Colorado and 66,000 AF in Wyoming in half of the years. An environmental impact assessment (see ENVIRONMENTAL ASSESSMENT beginning on page 108) considered the entire range of depletions represented by these annual averages, and management actions described in this plan were designed to offset the impacts of these depletions on the listed fishes. An intra-Service biological opinion pursuant to ESA Section 7 will be based on the best information currently available; however, if any of the assumptions/information upon which the opinion is based should change significantly in the future, it may be necessary for the Service to reinitiate consultation and supplement or amend its opinion on the implementation of this management plan. For example, if average annual depletions reach or exceed the estimated depletions considered by the Service in rendering its biological opinion (i.e., 155,000 AF/year in Colorado and 66,000 AF/year in Wyoming), the Service would likely reinitiate consultation. Therefore, annual water demand from the Yampa River Basin in Colorado and Wyoming will be quantified periodically, and average annual depletions will be estimated following a process similar to that used to estimate 1998 and 2045 depletions. In Colorado, the USBR prepares a Consumptive Uses and Losses Report (CULR) every 5 years, using information provided by the CWCB. Data from the CULR or State- approved demand estimate will be backcast over the 90-year CROSS period of record for the Yampa River to estimate annual depletions that would have occurred in each of the years of the hydrologic record. Averaging depletions over this period would minimize the influence of exceptional years and produce results more directly comparable to those projected future depletions that will be considered in the consultation. Every 5 years, beginning in 2005, the States of Colorado and Wyoming will report to the Recovery Program estimated average annual volumes of depletions from the Yampa and Little Snake rivers and their tributaries. When estimated average annual depletions reach 155,000 AF in Colorado or 66,000 AF in Wyoming, the Service is expected to reinitiate intra-Service consultation under ESA Section 7, and, depending upon the outcome of that consultation, this plan and/or the cooperative agreement with the Service to implement this plan may need to be modified or supplemented. ~ Management Plan for Endangered Fishes in the Yampa River Basin 30