USGS Water-Year Summary 2025
01401750 MILLSTONE RIVER AT GRIGGSTOWN, NJ
LOCATION - Lat 40°26'24", long 74°37'03" referenced to North American Datum of 1983, Montgomery Township, Somerset County, NJ, Hydrologic Unit 02030105, on left bank, 300 ft downstream from bridge at Griggstown, 200 ft downstream from Simonson Brook, and 300 ft downstream from Griggstown Causeway.
DRAINAGE AREA - 229 mi².
SURFACE-WATER RECORDS
PERIOD OF RECORD - Annual maximum, water years 1938, 1960-61, 1971, 1997, 1999 to current year. Miscellaneous measurements, water year 1969.
GAGE - Water-stage recorder with telemetry and crest-stage gage. Datum of gage is 25.50 ft above NAVD of 1988.
EXTREMES FOR PERIOD OF RECORD - Maximum gage height, 24.21 ft, Aug 28, 2011.