USGS Water-Year Summary 2018
12085500 LA GRANDE RESERVOIR AT LA GRANDE, WA
LOCATION - Lat 46°49'23", long 122°18'13" referenced to North American Datum of 1927, in SW 1/4 SE 1/4 sec.33, T.16 N., R.4 E., Thurston County, WA, Hydrologic Unit 17110015, at left end of gate control structure, 1.1 mi southeast of La Grande, 1.7 mi downstream from Alder Dam, and at mile 42.5.
DRAINAGE AREA - 289 mi².
PERIOD OF RECORD - January 1945 to current year. January 1945 to September 1951 included in combined adjustment to monthly flow of Nisqually River at La Grande. Month-end contents January 1945 to September 1950, published in WSP 1316.
GAGE - Water-stage recorder. Datum of gage is 7.61 ft below NGVD of 1929 (levels by City of Tacoma). Prior to June 12, 1947, month-end gage heights furnished by City of Tacoma from temporary gages in pool upstream from dam.
EXTREMES FOR PERIOD OF RECORD - Maximum contents, 2,760 acre-ft, May 14, 1950, gage height, 936.4 ft; minimum contents observed since reservoir first filled, 1,370 acre-ft, Aug. 24, 1956, gage height, 900.0 ft.