USGS Water-Year Summary 2024
12085000 ALDER RESERVOIR AT ALDER, WA
LOCATION - Lat 46°48'09", long 122°18'37" referenced to North American Datum of 1927, in SE 1/4 NW 1/4 sec.09, T.15 N., R.4 E., Thurston County, WA, Hydrologic Unit 17110015, near left end of Alder Dam on Nisqually River, 1.0 mi west of Alder, 1.7 mi upstream from La Grande Dam, 4.6 mi upstream from Mashel River, and at mile 44.2.
DRAINAGE AREA - 286 mi².
SURFACE-WATER RECORDS
PERIOD OF RECORD - November 1944 to current year.
GAGE - Water-stage recorder. Datum of gage is 7.61 ft below NGVD of 1929 (levels by Tacoma Public Utilities). Prior to July 8, 1946, nonrecording gage at same site and datum.
EXTREMES FOR PERIOD OF RECORD - Maximum contents, 233,848 acre-ft, Dec. 4, 1975, gage height, 1,207.68 ft; minimum contents since reservoir first filled, 70,430 acre-ft, Oct. 26, 2018, gage height, 1,134.23 ft.