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USGS Water-Year Summary 2024
08172000 San Marcos River at Luling, TX
LOCATION - Lat 29°39'58", long 97°39'02" referenced to North American Datum of 1927, Caldwell County, TX, Hydrologic Unit 12100203, at downstream side of bridge on State Highway 80, 0.9 mi south of U.S. Post Office at Luling, and 9.5 mi upstream from Plum Creek.
DRAINAGE AREA - 838 mi².
REVISIONS HISTORY - WSP 958: 1940. WSP 1312: 1940(M), 1945(M), 1947(M). WSP 2123: Drainage area.
SURFACE-WATER RECORDS
PERIOD OF RECORD - Apr. 1939 to current year.
PERIOD OF RECORD, Water-Quality.--
CHEMICAL DATA: Feb. 1944 to Feb. 1959, Sept. 1961 to Apr. 1966, Nov. 1968 to Aug. 1999.
BIOCHEMICAL DATA: Mar. 1963 to Aug. 1973.
PESTICIDE DATA: June 1986 to May 1999.
RADIOCHEMICAL DATA: Nov. 1980 to May 1981.
SEDIMENT DATA: Oct. 1960 to Apr. 1966.
GAGE - Water-stage recorder. Datum of gage is 322.210 ft. above NAVD of 1988. The NAVD of 1988 datum was determined by a level 2 GNSS survey (Reference Frame NAD_83 (2011) (EPOCH:2010.0000). (GEOID18) by USGS on December 12, 2024, and tied to RM9. Prior to December 12, 2024, the datum of gage was 322.05 ft. above NAVD of 1929. Prior to Oct. 21, 1988, at site 390 ft downstream at same datum. Satellite telemeter at station.
REMARKS - Water Year records fair. Since 1984, at least 10% of contributing drainage area has been regulated by discharge from the flood-detention pools of at least 18 floodwater-retarding structures. These structures control runoff from 105 mi² in the Town, Sink, and York Creek drainage basins. Some records listed in the "Period of Record" for surface water and water quality may not be available electronically. Dam at site, as well as diversion were worked on in 2015.
EXTREMES OUTSIDE PERIOD OF RECORD - Maximum stage since at least 1859, 40.4 ft in 1869 or 1870, from information by Texas Department of Transportation. Flood of May 29, 1929, reached a stage of 37.1 ft and is the second highest known.
EXTREMES FOR PERIOD PRIOR TO REGULATION - WATER YEARS 1939-1983: Maximum discharge, 57,000 ft³/s Sept. 12, 1952 (gage height, 34.95 ft); minimum daily, 43 ft³/s Aug. 12, 1951.
AVERAGE DISCHARGE FOR PERIOD PRIOR TO REGULATION - 44 years (water years 1939-83), 370 ft³/s (268,100 acre-ft/yr).
