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USGS Water-Year Summary 2024
08104700 North Fork San Gabriel River near Georgetown, TX
LOCATION - Lat 30°39'42", long 97°42'40" referenced to North American Datum of 1927, Williamson County, TX, Hydrologic Unit 12070205, on left bank 5,000 ft downstream from North Fork dam, 1.5 mi upstream from Middle Fork San Gabriel River, 2.7 mi upstream from Interstate Highway 35, 2.7 mi northwest of Georgetown, and 3.4 mi upstream from mouth.
DRAINAGE AREA - 248 mi².
REVISIONS HISTORY - WDR TX-76-2: Drainage area.
SURFACE-WATER RECORDS
PERIOD OF RECORD - June 1968 to current year.
PERIOD OF RECORD, Water-Quality.--
CHEMICAL DATA: Aug. 1978, Jan. 1981 to Aug. 1989.
BIOCHEMICAL DATA: Jan. 1981 to Aug. 1989.
RADIOCHEMICAL DATA: Apr. 1981.
GAGE -
Water-stage recorder. Satellite telemetry at station.
Datum of the gage: 689.262 ft NAVD88 based on Level 2 Static GNSS survey processed through OPUS, Ref Frame NAD83 (2011)(EPOCH:2010.0000) ITRF2014 (EPOCH:2024.6824) and Geoid 18. The survey was completed on September 6th, 2024, while occupying a TRM referenced to local gage datum via differential levels.
Prior to 9/6/2024, the Datum of the gage was 689.06 ft NGVD29 established from differential levels.
REMARKS - Records poor. Since water year 1980, at least 10% of contributing drainage area has been regulated. No flow at times. Some records listed in the "Period of Record" for surface water and water quality may not be available electronically.
EXTREMES OUTSIDE PERIOD OF RECORD - Maximum stage since at least 1875, 39.5 ft in Sept. 1921. Flood in Apr. 1957 reached a stage of 34.5 ft, from information by local residents.
EXTREMES FOR PERIOD PRIOR TO REGULATION -
WATER YEARS, 1968-1979: Maximum discharge, 35,000 ft³/s Sept. 17, 1974 (gage height, 26.20 ft); no flow July 23, 24, 25, 1971.
AVERAGE DISCHARGE FOR PERIOD PRIOR TO REGULATION - 11 years (water years 1969-79), 88.1 ft³/s (63,830 acre-ft/yr).
