USGS Water-Year Summary 2024

14234800 RIFFE LAKE NEAR MOSSYROCK, WA

LOCATION - Lat 46°32'07", long 122°25'25" referenced to North American Datum of 1927, in SW 1/4 SW 1/4 sec.10, T.12 N., R.3 E., Lewis County, WA, Hydrologic Unit 17080005, in emergency generator room on top of Mossyrock Dam on Cowlitz River, 2.8 mi east of Mossyrock, and at mile 65.5.

DRAINAGE AREA - 1,154 mi².

REVISIONS HISTORY - WDR WA-74-1: 1973.

SURFACE-WATER RECORDS

PERIOD OF RECORD - April 1968 to current year.

GAGE - Water-stage recorder; nonrecording gage prior to July 25, 1968. Datum of gage is NGVD of 1929 (levels by City of Tacoma).

REMARKS - Reservoir is formed by concrete arch dam, completed in April 1968; storage began Apr. 3, 1968. Useable capacity, 1,297,400 acre-ft between elevations 600 ft, minimum operating level, and 770 ft, normal operating pool. Unused storage below elevation 600 ft, 288,900 acre-ft. Crest of spillway is at elevation 728.5 ft and top of taintor gates are at elevation 778.5 ft. Water used by Tacoma Power for power generation. Figures given herein represent total contents. Capacity table furnished by Tacoma Power. Chemical analyses December 1973 to September 1983 (samples were taken near the dam).

EXTREMES FOR PERIOD OF RECORD - Maximum contents, 1,686,300 acre-ft, July 31, 1972, elevation, 778.63 ft; minimum contents since normal low operating level was attained, 517,233 acre-ft, Mar. 9, 2001, elevation, 644.93 ft.