Estimating Additional Water Yield from Changes in Management

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Prior to selecting Coon Cr•eek:, an intensive search for a suitable area was made throughout Region 2 and a portion of Region 3 of the Forest Service. Initially, it was hoped that an area could be selected that involved owriership by several government agf;ncies, the state, and the private sector - a true partnership. Initial discu:>sio:ns in the late 1970's and the early 1980's included the Denver Water Department, USDI Bureau of Land Management (BLM), USDA Soil Consei-vation Service (now NRCS), Colorado Division of Wildlife, Colorado Forf;st Service, and the State Engineer's Offices in Colorado and Arizona, as vvell as the Regional Foresters in Regions 2 and 3 (Troendle 1990). As the searc;h for a site proceeded, the site in Wyoming proved to be the only site a??ailable to meet technical objectives of the ' demonstration. In contrast to the perception that extensive areas exist for the application of the water yie;ld technology, search for the demonstration site presents testimony to the fact extensive land areas suitable for water yield ? augmentation are not readily available on National Forest System (NFS) lands in the inland west. Coon Creek, the treatment watershed, is a 4133 acre drainage located in the Sierra Madre Range on the Ha.yden District of the Medicine Bow National Forest (MBNF) in Wyon:ung. In 1982, 8-foot Cipoletti weirs were : constructed on each drainag e to monitor stream flow. By 1987, a suitable calibration had been achievi-ld (Bevenger and Troendle 1987) and design and implementation of the treatme:nt began. Initially the intent was to harvest ? approximately one-third o:f' the Coon Creek watershed, as was done in ' research at Fraser Experimental Forest. However, this was an operational effort and technical consiclerations, as well as compliance with resource \; - constraints imposed by the MBNF Forest Plan (primarily for miniinizing impairment of visual qualiry as; well as riparian and old-growth protecrion), reduced the opportunity for harvest. Although minimal in nature, these considerations and constrai:nts resulted in only 24 percent of the watershed area actually being impacteci by either road construction or rimber harvest. -- Although the length of the post-treatment record for Coon Creek is short (5 years), the impact the treati-ner.Lt had on seasonal water yield is quite clear. Removal of vegetation froni 217 percent of the area significantly inc-reased flow by an average of 3.0 inc:hes (Troendle et al. 1998). The increase is proportionally consistent with what has been observed to occur on small experimental watersheds elsewlzere, and extrapolation of empirical est:imates of change, based on proce;ss research at the Fraser Experimental Forest (Troendle and Reuss 1997), compare well with the observed changes at 15