USGS Water-Year Summary 2018
04117500 THORNAPPLE RIVER NEAR HASTINGS, MI
LOCATION - Lat 42°36'57", long 85°14'11" referenced to North American Datum of 1927, in SE 1/4 sec.27, T.3 N., R.8 W., Barry County, MI, Hydrologic Unit 04050007, on right bank 100 ft upstream from bridge on McKeown Road, 0.6 mi downstream from Cedar Creek, 2.0 mi downstream from Thornapple Lake, and 3.2 mi southeast of Hastings.
DRAINAGE AREA - 385 mi².
PERIOD OF RECORD - October 1944 to current year.
GAGE - Water-stage recorder and crest-stage gage. Datum of gage is 786.71 ft above NGVD 29 (levels by Michigan Department of Natural Resources). Prior to Oct. 1, 1965, nonrecording gage at same site and datum.
EXTREMES FOR PERIOD OF RECORD - Maximum discharge, 6,810 ft³/s, Apr. 7, 1947, gage height, 10.20 ft, from graph based on gage readings; minimum discharge, 33 ft³/s, Aug. 10, 1964.