Electrical Power for Valdez and the Copper River Basin-1981

slope of the two adjacent months of July and September, therefore, nocorrelation coefficient was derived. The relationships derived for thetwo stations are shown in Table A-4.The monthly streamflows for Allison Creek were not correlated withPower Creek sinc~ there were no records available for Allison. SolomonGulch's drainage area of 19.5 square miles better approximates the sizeof Allison's, so its extended streamflow values were used to derive'StreamflO\'I values for Allison Creel( rather than the Lowe Riverstreamflows with a drainage area of 222 square miles. Allison andSolomon are also iYl very close proximity to each other so they shouldhave similar hydrologic characteristics. The following table lists theoertinent characteristic'S of each basin.Area Mean Elevation % AreaCreek (M i 2) (Feet) in Gl aciersAllison 5. F)8 2,800 24Power 20.8 2, 140 25Solomon Gu 1 ch 19.5 2,300 21The monthly streamflow values for Power Creek were used to extend theperiod of record for Solomon Gulch; this extended period of record isshown in Table A-5. These values in turn were used along with a basinarea relationship to determine streamflows for those basins withoutdata. Allison Creek estimated streamflows were derived in this mannerand are shown in Table A-6.The four damsites considered as alternatives to the Allison Creekdevelopment had streamgages in fairly close proximity to two of them.The Klutina River and the Tonsina River are both gaged, but at locationsdownstream from the proposed damsites. For the Tonsina River, theaverage annual precipitation was estimated for the area above the dam andfor the area above the gage by use of isohyetal maps presented in a 1977U.S. Forest Service Water Resources Atlas. The ratio of the two areawideaverage precipitation values was then determined, and the ratio ofthe project-drained area to the gaged area was also determined, thenthese two were applied to the gaged streamflows to give the expectedflows at the sites.At the Klutina River site, no isonyets were available for most of thedrainage area, so streamflows were modified only on the basis of areadrained considering the Tsina River and Tiekel River sites, no streamflowrecords exist for these rivers. Solomon Gulch was selected as mostclosely representing the Tsina River, since it was the only fairlyheavily glaciated stream with flow records in the vicinity. Averageannual precipitation and drainage area comparisons were again made inorder to adjust the Solomon flows for the Tsina. Only the 7 years ofrecorded data from Solomon were used.Because of the approximately similar glaciated percentages, overalldrainage areas, and the proximity of the watersheds, Tiekel River flowsA-7