SURFACE-WATER RECORDS
LOCATION.--Lat 40°33'20", long 74°34'58" referenced to North American Datum of 1983, Bridgewater Township, Somerset County, NJ, Hydrologic Unit 02030105, on left bank at downstream side of bridge on North Main Street (Finderne Avenue) at Manville, and 1.4 mi upstream from Millstone River.
DRAINAGE AREA.--490 mi².
PERIOD OF RECORD.--June 1903 to March 1907 (published as "at Finderne"), August 1908 to April 1915 (gage heights only, published in WSP 521), August 1921 to current year. Monthly discharge only for some periods, published in WSP 1302.
REVISED RECORDS.--WSP 1552: 1904, 1906, 1922, 1923(M), 1924-25, 1926-29(M), 1930, 1932-33(M), 1924-54. WDR NJ-75-1: 1964(M), 1969(M), 1970(P), 1971(P), 1972(P), 1973(P), WDR NJ-02-1: 2000(M).
GAGE.--Water-stage recorder with telemetry. Datum of gage is 20.61 ft above NGVD of 1929. Prior to Aug 15, 1923, non-recording gage on downstream side of highway bridge at same site and datum. Between Jun 9, 1978 and Jun 7, 1979, gage temporarily relocated at site 1.4 mi downstream, just upstream from Millstone River, because of reconstruction of highway bridge. Between Oct 1, 2006 and Mar 9, 2008, gage temporarily relocated at site 0.4 mi downstream, just upstream of an abandoned railroad bridge, because of reconstruction of highway bridge.
REMARKS.--Records good, except for estimated discharges, which are fair. Records given herein represent flow at gage only. Slight diurnal fluctuation at low flow. Flow regulated at low flow by Spruce Run (station 01396790) and Round Valley Reservoirs. Diversion to Round Valley Reservoir since March 1966. Prior to Sep 1, 1986, the former Johns-Manville Corporation diverted water 1,500 ft upstream from station and returned to river 0.6 mi downstream from gage. Above 5.50 ft the stage-discharge relationship can be affected by variable-stage backwater from the confluence with the Millstone River. Oct 1, 1966 to present, water-stage recorder at station Raritan River at Bound Brook below Calco Dam (station 01403060) used as auxiliary gage when variable-stage backwater conditions exist. From Oct 1, 1952 to Sep 30, 1966, water-stage recorder at station 1,000 ft upstream from current location at station Raritan River at Bound Brook above Calco Dam (station 01403000) used as auxiliary gage. Discharges above 30,000 ft³/s from rating curve extension on basis of slope-area computation of peak flow.
EXTREMES FOR PERIOD OF RECORD.--Maximum discharge, 77,600 ft³/s, from rating curve extended above 15,000 ft³/s on basis of slope-area computation of peak flow, Sep 16, 1999, gage height 27.10 ft; maximum gage height, 27.49 ft, Sep 17, 1999; minimum discharge, 17 ft³/s, Sep 19, 1964.

WATER-QUALITY RECORDS
PERIOD OF RECORD.--
Water years 1923-25, 1959-74, 1976-97, 2008 to 2012.

CONTINUOUS DATA:
Dissolved Oxygen: August-September 2003, April 2008 to current year.
Dissolved Oxygen, Percent of Saturation: August-September 2003, April 2008 to current year.
pH: August-September 2003, April 2008 to current year.
Specific Conductance: August-September 2003, April 2008 to current year.
Water Temperature: August-September 2003, April 2008 to current year.
Turbidity: April 2008 to current year.
REMARKS.--The accuracy of continuous water-quality data can be found here.
EXTREMES FOR PERIOD OF DAILY RECORD.--
DISSOLVED OXYGEN, PERCENT OF SATURATION: Maximum, 169%, July 30 2014; minimum, 58%, May 29 and 30, 2016.
pH: Maximum, 9.5 standard units, Mar 1, 2, 2009; minimum, 6.8 standard units, Dec 12, 13, 2008, Dec 27, 2009, Jul 1 and 2, 2013, May 1 2014, July 31, 2016 and August 1, 2016.
SPECIFIC CONDUCTANCE: Maximum, 3,190 microsiemens/cm, Feb 02, 2011; minimum, 86 microsiemens/cm, Sep 8, 2011.
WATER TEMPERATURE: Maximum, 32.1°C, Jul 22,23, 2011; minimum, -0.3°C, Dec 27, 2010.
TURBIDITY: Maximum, 1,200 FNU, Mar 30, 2009; minimum, <0.5 FNU on many days.


Peak Flood Chart

National Weather Service flood stage for this gage is 14.0 ft.

Forecasts for this gage are issued by the National Weather Service routinely year-round.
Forecast information is available here.