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U r-. t) . '- , ,~ '. '- " '\,.,..>' .- I..' a l":\ '<." /-. ':....;'; 0 ,;") ,",,, (~ ~ t-'!!, -\..r {': ~,,.i t~;. "'-,; /"' t..! () ('\ -. C ~MifliL.. Stillwater Res. Bear River - tributary to Yampa R. 6200 Freeman Res. Little Cottom/ood Cr. .- tributary to Fortific:ation Creek 1.6 115 Hahn" Peak Res. Willow Creek _. tributary to Ink R. 7 600 Elkhead Lake Elkhead Creek - tributary to" Yampa R. 212 13700 Ralph White Res. Fortification Creek- tributary to Yampa R. 220 605 3. ~:limatolo!\l. - The climate of the area is generally semi-arid:. The high mountains are comparatively wet and cool whereas the lower areas are dryer and warmer. The Pacific Ocean and the Gulf of Me~dc:o are the primary moisture sources. Air-masses from these sources lose much of their moisture as they cross high mountain ranges prior to E'tltering the Yampa River basin. Generally, air-masses from the Pacific: Ocean dominate from October through April while during the late spr:lng and summer air-masses from the Gulf of Mexico are dominant. A normal annual precipitation map and a listing of climat,a s.tations in the area are shown on chart 3. Average: annual precipitation at Craig is about 13.8 inches. During the winter most of the precipitati.on falls as snow. Thunderstorms are connnon during the summer. The maxi.mum hourly rainfall at Craig was 2.04 inches ~md was recorded on :7 i\.ugust 1970. 4. Etreamflow records - Records of streaDulow are available at 45 locations within the Yampa River basin. These locations are H.sted on Tab 1(, 1. 5. l'lood history - Flood flows on the Yalllpa River and its tr:lbutaries are (:aused primarily by snowmelt during the March through .lun.. period. On o(,casion these floods have been augmented by rain and result in substantially higher peak flows than would be expected from sno"'IIlelt alone. Snowmelt floods are characterized by moderate peaks, large volumes, and long durations. Thunderstorms occur in the summer and fall and c:an produce high peak flows from small areas. These storms do not produce high flows on the larger streams because of the limited a.real coverage. Thunderstorms are characterized by high peaks, low volumes, and short durations. The largest floods of record on the Yampa River are listed in the following table. 2 "'If'" 'tt "