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. Colorado Water Conservation Board and the USBR, Durango Area Office. The watershed map is presented as Exhibit I, and the HEC-I Summary is in Appendix A. TABLE 1 USGS STREAM GAGES Gage Name USGS Drainage Area Gage Period Gage Number (Square Miles) Elevation of Record Los Pmos River at La Boca, CO 09354500 510,0 6144 1950 to Present Spring Creek at La Boca, CO 09355000 58.0 6160 1950 to Present Vallecito Creek near Bayfield, CO 09352900 72.1 7906 1962 to Present Unit Hydrograph Computation . The Albuquerque District adopted Snyder's synthetic method to compute unit hydro graphs for the subareas in the watershed model. Snyder's method draws a relationship between measurable physical characteristics ofa drainage basin and the basin's unit hydrograph, The U.S, Army Corps of Engineers' Engineering Manual EM 1110-2-9021, Flood Runoff Analysis, dated II October 1991, describes Snyder's unit hydrograph method and provides the following equation to compute the time to peak (tp): tp = C, x (L X L,,)O.3 L = Total travel length in miles Lca Travel length to the centroid of the basin in miles Ct = Time-to-peak coefficient The C,-versus-slope curve generated by the Albuquerque District for Rio Puerco and Rio Salado basins served as the basis for development of the C, coefficient and the Cp (peaking) coefficient. The HEC-l model generates unit hydrographs based on the tp and Cp values. This Ct- versus-slope curve has been used successfully for the San Juan River watershed and, therefore, is considered appropriate for the Los Piiios River watershed, Channel Routing . The Albuquerque District used the Muskingum-Cunge routing method to model the Los Pmos River channel in the HEC-I model. The stream routing method employs typical eight-point cross sections to represent each channel and overbank reach, Based on field investigations, a Manning's 3