Electrical Power for Valdez and the Copper River Basin-1981

were estimated based on Tonsina River flows. As with the Tonsina site,precipitation and area rati()s were used to generate the Tiekel flows fromthe Tonsina's.The pertinent characteristics for each site are shown below:GageCreek Gage Used% Average AverageArea in Annual Gage AnnualArea Glaciers Precip. Area Precip.(mi2) ( in) (rli2) ( in)Overa 11RatioKlutina Klutina 826 5 -1 0 880Tiekel Tonsina 367 15 53. 1 420 28.0Tonsina Tonsina 263 10 32.9 420 28.0Ts ina Solomon 5'1 50 70.4 19 1 140.941.660.741. 79Estimated Damsite Streamflows:It has been assumed that the streamflows determined through theprevious analysis would be the estimated damsite streamflows.~v aporat ion:The normal high relative humidity, high percentage of overcast days,and cool climate preclude any appreciable loss from evaporation.Estimates of flow were based on records of existing or historical gagingstations near the project areas, and include evaporation from the streamsurface. Due to the nortllern latitude and prevailing maritime climate,additional evaporation from the reservoir surface would beinsignificant.Flood Characteristics:Snowmelt-type floods are dependent upon two conditions: (1) theamount of accumulated snow; and (?) the temperature sequence during thespring melt period. A 1 arge snowpack over the basin will give a 1 argevolume of runoff during the spring. However, if the temperaturesincrease gradually, causing slower snowmelt, the flood peak will be justslightly above normal. If the early spring is colder than normal andthen tile temperatures rise rapidly for a prolonged period, the flood peakwill be extremely high with the duration of flooding dependent upon thetotal snowpack.On the streams in the southern portion of the study area, rainfloodsproduce the highest flm ... s. These occur in the fall, generally betweenlate August and October. The flood peaks are quite sharp due to the fastrunoff, which is caused by the steepness of the terrain and the lowinfiltration losses into the underlying rock. On the Klutina and TonsinaRivers, the flooding characteristics are mixed. The annual peak flows onA-8