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Water-Year Summary for Site 01646500

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  • Water-Year Summary reports summarize a year of hydrologic data in a printer-friendly format.
  • For water years 2014 onward, choose a water year and parameter and an on-demand Water-Year Summary report will be generated.
  • For water years 2006 through 2013, choose a water year and an Annual Water Data Report will be provided.
  • For water years 2005 and earlier, Annual Water Data Reports may be available in digital format.
  • Not all sites have reports available for every water year.
Available Parameters
00010 Temperature, water(Max.,Min.,Mean) [Discontinued]  
00010 Temperature, water(Max.,Min.,Mean) [Discontinued]  
00010 Temperature, water(Max.,Min.,Mean) [Discontinued]  
00010 Temperature, water(Min.,Max.,Mean)  
00010 Temperature, water(Max.,Min.,Mean) [Discontinued]  
00060 Discharge(Mean)  
00095 Specific cond at 25C(Max.,Min.,Mean)  
00095 Specific cond at 25C(Max.,Min.,Mean) [Discontinued]  
00095 Specific cond at 25C(Max.,Min.,Mean) [Discontinued]  
00300 Dissolved oxygen(Max.,Min.,Mean)  
00300 Dissolved oxygen(Max.,Min.,Mean) [Discontinued]  
00400 pH(Max.,Min.,Med.)  
00400 pH(Max.,Min.,Med.) [Discontinued]  
63680 Turbidity, Form Neph(Max.,Min.,Mean)  
63680 Turbidity, Form Neph(Mean,Max.,Min.) [Discontinued]  
99133 NO3+NO2,water,insitu(Max.,Mean,Min.)  
99133 NO3+NO2,water,insitu(Max.,Min.,Mean) [Discontinued]  

Water year 2024: 2024-10-01 to 2025-09-30
 
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USGS Water-Year Summary 2024
01646500 POTOMAC RIVER NEAR WASHINGTON, DC
LOCATION - Lat 38°56'59.2", long 77°07'39.5" referenced to North American Datum of 1983, Montgomery County, MD, Hydrologic Unit 02070008, on left bank just upstream from Little Falls Dam, 1 mi upstream from District of Columbia boundary line, 1.2 mi upstream from Chain Bridge, 1.8 mi east of Langley, Fairfax County, and at mile 117.4.
DRAINAGE AREA - 11,560 mi².
REVISIONS HISTORY -
  • WSP 726: Drainage area.
  • WDR MD-DE-75-1: 1973-74(M).
  • https://waterdata.usgs.gov/nwis/dv/?site_no=01646500: 2018.
  • https://waterdata.usgs.gov/nwis/uv/?site_no=01646500: 2021.
  • Discharge for Measurement 385 made on 06/25/2021 was revised on 09/22/2021 due to an error in computation.
SURFACE-WATER RECORDS
PERIOD OF RECORD - March 1930 to current year.
GAGE - Water-stage recorder, crest-stage gage, and concrete control. Datum of gage is 37.20 ft above North American Vertical Datum of 1988. Prior to June 7, 1930, nonrecording gage, and June 7, 1930 to Jan. 22, 1965, water-stage recorder at site 1 mi upstream on right bank at same gage datum.
REMARKS -
  • Water Years 2022-2023: Records fair, except those for estimated discharges, which are poor.
  • Water Years 2017-2021: Records good, except those for estimated discharges, which are poor.
  • Water Years 2014-2016: Records good, except those for estimated daily discharges, which are poor.
  • Water Year 2013 and prior years’ accuracy statements can be found in Annual Water Data Reports.

    • Diversions since June 1959. For unregulated statistics of monthly mean data and summary statistics for water years 1930 to 1958, reference WDR MD-DE-DC-02-1. Diversions at Great Falls through aqueducts since June 1959, from gage pool at Little Falls Dam; since October 1958, at Rockville Filtration Plant; since April 1961, at Potomac Filtration Plant; since October 1961, at Fairfax Water Treatment Plant (from Goose Creek); since April 1964, at Violets Lock to Chesapeake and Ohio Canal; and since October 1985, at Fairfax County Water Authority Treatment Plant. Low flow affected slightly prior to July 1981 by Stony River Reservoir, since December 1950, by Savage River Reservoir (see station 01597500), and since July 1981, by Jennings Randolph Lake. U.S. Geological Survey satellite data-collection platform at station.
    EXTREMES OUTSIDE PERIOD OF RECORD - Flood of June 2, 1889, was of approximately the same magnitude as that of March 19, 1936.
    WATER-QUALITY RECORDS
    PERIOD OF RECORD - Water years 1989 to current year.
    PERIOD OF DAILY RECORD - SPECIFIC CONDUCTANCE: October 1988 to current year. WATER TEMPERATURE 7.1 ft from riverbed (top): October 1988 to September 2019. WATER TEMPERATURE 4.1 ft from riverbed (middle): July 2006 to September 2019. WATER TEMPERATURE 1.0 ft from riverbed (bottom): July 2006 to September 2019. NITRATE PLUS NITRITE IN SITU (BURST data collection): December 2011 to current year. NITRATE PLUS NITRITE IN SITU (SDI-12 data collection): July 2019 to current year.  SPECIFIC CONDUCTANCE, MULTIPARAMETER SONDE: November 2013 to current year. TEMPERATURE, MULTIPARAMETER SONDE: November 2013 to current year. pH: November 2013 to current year. DISSOLVED OXYGEN: November 2013 to current year. TURBIDITY: November 2013 to current year.
    INSTRUMENTATION - Water-quality monitor (top) October 1988 to September 2019.

    Water temperature probes (middle, bottom) July 2006 to September 2019.

    Suna V1 with external wiper (BURST data collection) December 2011 to June 2019.

    Suna V1 with external wiper (SDI-12 data collection) July 2019 to current year.

    MULTIPARAMETER SONDE November 2013 to current year.
    REMARKS - Missing record due to instrument malfunction or site servicing.
    EXTREMES FOR PERIOD OF DAILY RECORD -

    SPECIFIC CONDUCTANCE: Maximum, 1,820 microsiemens/cm (road salt influence), Feb. 6, 2004; minimum, 67 microsiemens/cm, Jun. 27, 2006.

    WATER TEMPERATURE 7.1 ft from riverbed (top): Maximum, 35.3°C, July 24, 2010; minimum, -0.1°C, Dec. 22-25, 31, 2000, Jan 2, 3, 10, 2001, Jan. 16-22, 25, Feb. 6, 2009, Jan. 3, 4, 2010, Jan. 7-10, 22-30, 2014 and Feb.1, 2014.

    WATER TEMPERATURE 4.1 ft from riverbed (middle): Maximum, 34.0°C, July 23, 2011 and July 8, 2012; minimum, -0.5°C, Feb. 7, 8, 12, 2010.

    WATER TEMPERATURE 1.0 ft from riverbed (bottom): Maximum, 33.5°C, July 8, 2012; minimum, -0.3°C, Jan. 16, 17, 2009, Feb 16, 2015.

    NITRATE PLUS NITRITE IN SITU (BURST collection): Maximum 2.21 mg/L as N, November 11, 12, 2012; minimum, 0.08 mg/L as N, September 14, 2016.

    NITRATE PLUS NITRITE IN SITU (SDI-12 collection): Maximum 2.06 mg/L as N, first occurrence on 12/19/2023 @21:30; minimum 0.04 mg/L as N, 09/08/2023 @14:30 (updated11/29/2023)

    Since 2019, a multiparameter sonde has been operating.

    DISSOLVED OXYGEN: Maximum, 16.3 mg/l, February 4, 2023; minimum, 5.0 mg/l, August 14, 2021.

    TURBIDITY: Maximum, 308 FNU, November 01, 2019; minimum, 0.4 FNU, December 24, 2021. 

    pH: Maximum, 9.1*, May 27, 2023; minimum, 6.9, July 9, 2022.

    WATER TEMPERATURE, MULTIPARAMETER SONDE: Maximum, 33.5°C, July 25, 2016; minimum, -0.1°C, various.

    SPECIFIC CONDUCTANCE, MULTIPARAMETER SONDE: Maximum, 1400 microsiemens/cm, December 16, 2020; minimum, 84 microsiemens/cm, September 01, 2021.

    *Multiple occurrences of the same extreme in selected dataset.