USGS Water-Year Summary 2019
04116500 Flat River at Smyrna, MI
LOCATION - Lat 43°03'10", long 85°15'53" referenced to North American Datum of 1927, in SE 1/4 NW 1/4 sec.28, T.8 N., R.8 W., Ionia County, MI, Hydrologic Unit 04050006, on right bank at downstream side of former bridge on Ingalls Road, 0.5 mi south of Smyrna.
DRAINAGE AREA - 528 mi².
PERIOD OF RECORD - October 1950 to September 1986 (operated as a continuous-record gaging station), water years 1993 to current year.
GAGE - Water-stage recorder. Datum of gage is 729.53 ft above NGVD 29 (levels by Michigan Department of Natural Resources).
EXTREMES FOR PERIOD OF RECORD - Maximum discharge, 4,700 ft³/s, Sept. 13, 1986, gage height, 9.05 ft; minimum (water years 1951-86), 7.4 ft³/s, Sept. 9, 1953.