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(1008JO DRAFT FINAL DRAFT - 12119/91 THE PIEDRA RIVER - PHYSICAL AND BIOLOGICAL SETrING The Piedra River is a tribulary of the San Juan River. The Piedra originates at the Continental Divide; the headwater streams include the East and West Forks of the Piedra River, Williams Creek, Weminucl1e Creek, and Sand Creele. First Forie is also an imponant tributary. The Piedra River flows into Navajo Reservoir near the Colorado. New Mexico state line. There are approximately 235,760 acres (386 mP) in the Piedra River watershed upstream aftbe point where the river crosses Highway 160 betWeen Bayfield and Pagosa Springs. See Figure A. Approximately 14,400 acres are privately or State owned and the remainder is National Forest System lands. Of the 14,400 acres, approximately 660 acres are to be acquired by the Forest Service through a donation from The Nature Conservancy. The proposed Piedra Wilderness includes anJy Nation.a.l Forest System lands and 47,490 of the total 53,100 acres are within the Piedra River watershed. There are 9.7 miles of the mainstem of the river from Section 18, TI6N, R3W above Sand Creek to Section 20, 115N, R4W below Indian Creek within the proposed wilderness. The proposed wilderness includes the lower portions of the Sand Creek. Firn For.. Sheep Creel:. and Indian Creel: watenbeds, Based on records from the USGS stream gage which was located near the present Highway 160 bridge, average annual water yield from the Piedra River is 219,765 acre-feet. This gage, Piedra River at Piedra (Station 39495(0), was operated continuously from 1938 to 1973 and has 33 complete years of record (from 1940 to 1972), Total annual yield and the pattern of runoff vary substantially from year to year. In terms of annual yield, 1941 was the wettest year of record (533.293 acre-feet) and 1959 was the driest (89,565 acre-feet). See Figure B. ANNUAL HYDROGRAPHS - i'trdr. II i'tedn 1t41 - ......f'flest Year of RKont IJ~' - Driest Year of RKord :r :?:: f ::5001 ~ 2000 I ~ \jOO I I '000' ~~- ,~, --................ - , \.--j" J"v ~ ~:_~~_~_..~~~~~~~~z~~~~~~ _ ~ N ~ ~ ~ ~ ~ ~ _ _ ~ ~ _ ~ ~ ~ ~ ~ - ~ ;::-;;,~......~ Figure B Page 5