USGS Water-Year Summary for Site 08151500

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	Available Parameters
	00060 Discharge(Max.,Min.,Mean)
	00065 Gage height(Max.,Min.,Mean)

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

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USGS Water-Year Summary 2024

08151500 Llano River at Llano, TX

LOCATION - Lat 30°45'04", long 98°40'10" referenced to North American Datum of 1927, Llano County, TX, Hydrologic Unit 12090204, on right bank in Llano, 0.4 mi downstream from bridge on State Highway 16, 7.0 mi upstream from Little Llano River, and 29.3 mi upstream from mouth.

DRAINAGE AREA - 4,197 mi² of which 5 mi² probably is noncontributing.

REVISIONS HISTORY - WDR TX-81-3: Drainage area.

SURFACE-WATER RECORDS

PERIOD OF RECORD - Sept. 1939 to current year. PERIOD OF RECORD, Water-Quality.-- CHEMICAL DATA: Apr. 1948 to Oct. 1967, Apr. 1979 to Aug. 1986. BIOCHEMICAL DATA: Apr. 1979 to Aug. 1986. BIOLOGICAL DATA: Apr. 1979 to Aug. 1986. SEDIMENT DATA: Sept. 1964, Apr. 1979 to Aug. 1986. RADIOCHEMICAL DATA: Mar. to July 1981. TAXONOMIC DATA: May 1979 to Sept. 1981. PERIOD OF DAILY RECORD, Water-Quality.-- SPECIFIC CONDUCTANCE: Apr. 1979 to Sept. 1980. WATER TEMPERATURE: Apr. 1979 to Sept. 1980.

GAGE -

Water-stage recorder. Satellite telemetry at station.

Datum of the gage: 970.08 ft NAVD88 based on a Level 2 Static GNSS survey processed through OPUS, Ref Frame: NAD83 (2011)(EPOCH:2010.0000) ITRF2014 (EPOCH:2024.1962) and Geoid 18. The survey was completed on March 12th, 2024, while occupying a TRM referenced to local datum via differential levels.

Prior to 3/12/2024, the datum of the gage was 970.01 ft NGVD29. Radio telemeter at station.

COOPERATION - Lower Colorado River Authority provides operation and maintenance of the gage and verification of stage-discharge relation at low stages. U.S. Geological Survey maintains stage-discharge relation at medium to high stages, computes and publishes streamflow record.

REMARKS - Records fair, except for estimated discharges and discharges below 5 cfs, which are considered poor. No known regulation or diversions. Part of the flow of the Llano River disappears into various formations, many of which are faulted, between Llano River near Junction (station 08150000) and this station. 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 1879, 41.5 ft, June 14, 1935, discharge, 380,000 ft³/s, from information by local resident.