USGS Water-Year Summary 2020
12025100 CHEHALIS RIVER AT WASTEWATER TREATMENT PLANT, AT CHEHALIS, WA
LOCATION - Lat 46°39'40", long 122°58'58" referenced to North American Datum of 1927, in NE 1/4 NW 1/4 sec.31, T.14 N., R.2 W., Lewis County, WA, Hydrologic Unit 17100103, on right bank at City of Chehalis old (abandoned) wastewater treatment plant, 0.25 mi downstream from State Highway 6 bridge, and at mile 74.3.
DRAINAGE AREA - 618 mi².
PERIOD OF RECORD - Water years 1999, 2000 (annual maximum). October 2000 to current year (seasonal records).
GAGE - Water-stage recorder and crest-stage gage is NAVD of 1988. Prior to May 8, 2018 at same site at datum NGVD of 1929 (levels by Lewis County).
EXTREMES FOR PERIOD OF RECORD - Maximum elevation, 180.58 ft, Dec. 4, 2007, at datum then in use.