USGS Water-Year Summary for Site 01645762

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	Available Parameters
	00010 Temperature, water(Max.,Mean,Med.,Min.)
	00060 Discharge(Mean)
	00095 Specific cond at 25C(Max.,Min.,Mean,Med.)
	00300 Dissolved oxygen(Max.,Min.,Mean,Med.)
	00400 pH(Max.,Min.,Med.)
	63680 Turbidity, Form Neph(Mean,Med.,Max.,Min.)
	99133 NO3+NO2,water,insitu(Med.,Min.,Max.)

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Water year 2024: 2024-10-01 to 2025-09-30

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USGS Water-Year Summary 2024

01645762 SOUTH FORK LITTLE DIFFICULT RUN ABOVE MOUTH NEAR VIENNA, VA

LOCATION - Lat 38°54'31.6", long 77°20'18.8" referenced to North American Datum of 1927, Fairfax County, VA, Hydrologic Unit 02070008, on right bank 1.3 mi downstream from State Highway 665, 0.1 mi upstream from mouth, and 4.4 mi west of Vienna.

DRAINAGE AREA - 2.71 mi².

SURFACE-WATER RECORDS

PERIOD OF RECORD - September 2007 to current year.

GAGE - Water-stage recorder. Datum of gage is 275.16 ft (+/- 0.14 ft) NAVD of 1988, from Level II OPUS-RS survey conducted on Mag Nail on Jan. 13, 2016.

WATER-QUALITY RECORDS

PERIOD OF RECORD - October 2007 to current year.

PERIOD OF DAILY RECORD -
DISSOLVED OXYGEN: June 2011 to current year.
NITRATE: October 2016 to current year.
pH: October 2007 to current year.
SPECIFIC CONDUCTANCE: October 2007 to current year.
TURBIDITY: October 2007 to current year.
WATER TEMPERATURE: October 2007 to current year.

INSTRUMENTATION - Water-quality and nitrate monitors. Electronic data logger with 15-minute recording interval.

EXTREMES FOR PERIOD OF DAILY RECORD -
DISSOLVED OXYGEN: Maximum: 15.1 mg/L, Jan. 4, 2012, but may have been higher during periods of missing record; minimum: 3.8 mg/L, Aug. 20, 2011, buy may have been lower during periods of missing record.
NITRATE: Maximum: 4.03 mg/L as N, Dec. 24, 2016, but may have been higher during periods of missing record; minimum: 1.22 mg/L as N, Dec. 6, 2016, but may have been lower during periods of missing record.
pH: Maximum: 8.9 standard units, Feb. 4, 2008, but may have been higher during periods of missing record; minimum: 6.0 standard units, Sept. 8 and 9, 2011 and Oct. 13, 14, 2012, but may have been lower during periods of missing record.
SPECIFIC CONDUCTANCE: Maximum: 1620 microsiemens/cm, Feb. 23, 2015, but may have been higher during periods of missing record; minimum: 23 microsiemens/cm, Oct. 13, 14, 2012, but may have been lower during periods of missing record.
TURBIDITY: Maximum: 1,820 FNU, Apr. 21, 2008, but may have been higher during periods of missing record; minimum: 0.0 FNU, on several days.
WATER TEMPERATURE: Maximum: 29.0 °C, July 24, 2010, but may have been higher during periods of missing record; minimum: -0.1 °C, Jan. 21, 25, 2008.
NITRATE: