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
Funding for this site is provided by:
Lat 40°28'30", long 74°34'33"
referenced to North American Datum of 1983, Hillsborough Township,
Somerset County, NJ, Hydrologic Unit 02030105, on left bank 30 ft
downstream from highway bridge on Blackwells Mills Causeway at
Blackwells Mills, 0.3 mi downstream from Six Mile Run, and 2.0 mi south
of Borough of Millstone.
PERIOD OF RECORD.--
June 1903 to December 1904 (gage heights
only), August 1921 to current year. Monthly discharge only for some
periods, published in WSP 1302. Published as "at Millstone"
WSP 1552: 1924-25(M), 1926. WDR US-2011: 1999,
Water-stage recorder with telemetry. Concrete control
since Nov 18, 1933. Datum of gage is 26.97 ft above NGVD of 1929. June
27, 1903 to Dec 31, 1904, non-recording gage at bridge 2.0 mi
downstream at Millstone at different datum. Aug 4, 1921 to Aug 16,
1928, non-recording gage at present site and datum.
Records good, except for estimated discharges and
discharges greater than 2,000 ft3
/s, which are fair. Inflow
from and losses to Delaware and Raritan Canal upstream of station. Flow
slightly regulated by Carnegie Lake, capacity, 310,000,000 gal and
several smaller reservoirs, combined capacity, 49,800,000 gal.
EXTREMES FOR PERIOD OF RECORD.--
Maximum discharge, 22,200
/s, Aug 28, 1971, gage height, 18.68 ft, from high-water
mark, maximum gage height, 21.24 ft, Aug 28, 2011, maximum discharge
occurred during different floodplain conditions; minimum discharge, 5.0
/s, Sep 16, 1923.
PERIOD OF RECORD.--
Water years 1962-69, 1973, 1976-80, 1991 to
Discrete water-quality data were collected as part of
New Jersey Ambient Surface-Water-Quality Monitoring Network
National Weather Service flood stage for this
gage is 9.0 ft.
Forecasts for this gage are issued by the National Weather Service
Forecast information is available here.