During winter months, cold and ice may result in inaccurate real-time gage height and streamflow data. Adjustments or deletions of this data can only be done after detailed analysis.

 

SURFACE-WATER RECORDS
LOCATION.--Lat 40°34'14", long 74°40'45" referenced to North American Datum of 1983, Branchburg Township, Somerset County, NJ, Hydrologic Unit 02030105, on right bank, 400 ft upstream from U.S. Route 202, 1.4 mi upstream from confluence with South Branch Raritan River, and 2.7 mi west of Raritan.
DRAINAGE AREA.--190 mi².
PERIOD OF RECORD.--June 1923 to current year. Monthly discharge only for June 1923, published in WSP 1302. Prior to October 1943, published as "at Milltown".
REVISED RECORDS.--WSP 1552: 1924-26, 1928-35. WDR NJ-79-1: 1971-78(P). WDR US-2011: 1997(P), 2004-10(P).
GAGE.--Water-stage recorder with telemetry. Concrete control since Sep 1, 1936. Datum of gage is 50.43 ft above NGVD of 1929. Prior to Oct 17, 1936, non-recording gage at site 30 ft downstream at same datum.
REMARKS.--Records good, except for estimated discharges, which are fair. Stage-discharge relationship affected by variable-stage backwater from the confluence with the South Branch Raritan River. From Dec 10, 2010 to present, water-stage recorder at North Branch Raritan River at South Branch (station 01400010), located just above the confluence with South Branch Raritan River, used as auxiliary gage when stage is above 3.40 ft to adjust for variable backwater. Some releases from Round Valley Reservoir enter stream upstream from gage. Occasional regulation due to gate operation at Ravine Lake, 13.8 mi upstream.
EXTREMES FOR PERIOD OF RECORD.--Maximum discharge, 29,000 ft³/s, Sep 16, 1999, gage height, 18.98 ft; minimum discharge, 3.0 ft³/s, Nov 28, 1930, as a result of probable temporary regulation.

WATER-QUALITY RECORDS
PERIOD OF RECORD.--Water years 1923-25, 1960-76, 1978-80, 1997 to current year.
PERIOD OF DAILY RECORD.--DISSOLVED OXYGEN: September 2009.
DISSOLVED OXYGEN, PERCENT OF SATURATION: September 2009. pH: September 2009. SPECIFIC CONDUCTANCE: September 2009. WATER TEMPERATURE: September 2009.
REMARKS.--Discrete water-quality data were collected as part of the New Jersey Ambient Surface-Water-Quality Monitoring Network.

Peak Flood Chart

National Weather Service flood stage for this gage is 10.0 ft.

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