USGS Water-Year Summary for Site 02236125

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	Available Parameters
	00010 Temperature, water(Max.,Min.,Mean)
	00060 Discharge(Mean)
	00065 Gage height(Mean)
	00095 Specific cond at 25C(Max.,Min.,Mean)
	00300 Dissolved oxygen(Max.,Min.,Mean)
	63160 Stream level, NAVD88(Mean)
	63680 Turbidity, Form Neph(Mean)
	72137 Discharge,tide fltrd(Mean)

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Water year 2023: 2022-10-01 to 2023-09-30

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USGS Water-Year Summary 2023

02236125 ST. JOHNS RIVER AT ASTOR, FL

LOCATION - Lat 29°10'00", long 81°31'20" referenced to North American Datum of 1927, in NW 1/4 sec.29, T.15 S., R.28 E., Volusia County, FL, Hydrologic Unit 03080101, near center of channel on bridge pile under bridge on State Highway 40, 0.4 mi northeast of Astor, 6.6 mi west of U.S. Highway 17, and 127 mi upstream from mouth.

DRAINAGE AREA - 3,330 mi².

SURFACE-WATER RECORDS

PERIOD OF RECORD - September 1931 to July 1934 (daily gage heights and miscellaneous discharge measurements only), February 1994 to September 2010, October 2010 to current year (filtered).

GAGE - Water-stage recorder, acoustic velocity meter, and data-collection platform. Datum of gage is at NGVD of 1929 and 1.11 ft below NAVD of 1988. Prior to Oct. 1, 2010, at datum 0.089 ft lower.

COOPERATION - This gage is monitored in cooperation with the St. Johns River Water Management District.

REMARKS - Streamflow at this site is significantly affected by astronomical tides. Daily mean discharge was computed from filtered unit value discharge data. The Godin low-pass filter was used to remove principal tidal frequencies from unit values. By convention, the U.S. Geological Survey has established ebb (seaward) flows as positive flow and flood (landward) flows as negative flows. The residuals are not total freshwater flows but are a combination of freshwater flows and water storage caused by higher and lower mean sea levels and storm surges from tropical storm events. Instantaneous discharge computed from index-velocity linear regression relation and gage height rating.

WATER-QUALITY RECORDS

PERIOD OF DAILY RECORD -

SPECIFIC CONDUCTANCE:  December 2007 to September 2016 (discontinued).
WATER TEMPERATURE:  December 2007 to September 2016 (discontinued).
DISSOLVED OXYGEN:  July 2008 to September 2016 (discontinued).
TURBIDITY:  July 2008 to September 2015 (discontinued).

INSTRUMENTATION - Water-quality monitor and data-collection platform.

REMARKS - Extremes for current year and extremes for period of daily record are based on recorded values and may have been exceeded during periods of no record. December 2007 to September 2008, published as daily mean; October 2008 to current year, published as instantaneous maximum and minimum. October 2014 to September 2016; water temperature, specific conductance, and dissolved oxygen, published as instantaneous maximum and minimum, and daily mean. Period of record extremes updated to reflect instantaneous maximum and minimum. Turbidity data is collected using a YSI 6136 optical turbidity probe. The manufacturers stated precision is +/-2% of the reading or +/-0.3 NTU, whichever is greater. Computed daily values between -0.3 and zero are reported as 0.0 FNU to account for this error. Formazin Nephelometric Unit values below 10 are reported to the nearest 0.1 FNU.

EXTREMES FOR PERIOD OF RECORD -

SPECIFIC CONDUCTANCE: Maximum, 1,800 µS/cm @ 25 °C, July 29, 30, 2011; minimum, 380 µS/cm @ 25 °C, Sept. 13, 2008; maximum daily mean, 1,300 µS/cm @ 25 °C, July 12, 13, 2015; minimum daily mean, 541 µS/cm @ 25 °C, Dec. 17, 22, 23, 2014.

WATER TEMPERATURE: Maximum, 33.9 °C, July 12, 28, 2016; minimum, 7.3 °C, Jan. 11, 2010; maximum daily mean, 32.9 °C, July 14, 2016; minimum daily mean, 12.6 °C, Jan. 24, 2016.

DISSOLVED OXYGEN: Maximum, 13.0 mg/L, Mar. 6, 7, 2009; minimum, 0.0 mg/L, Sept. 13-18, 2008, Oct. 1, 2008; maximum daily mean, 9.1 mg/L, Jan. 24, 25, 2016; minimum daily mean, 1.9 mg/L, Aug. 28, 2016.

TURBIDITY: Maximum daily mean, 22.0 FNU, Aug. 22, 2008; minimum daily mean, 0.6 FNU, Jan. 19, 20, 2013.