For Friday, it will be hot with mostly sunny skies across the basin with high temperatures reaching the mid 90s and heat index values in the upper 90s and low 100s. Winds will be light from the south and southeast at 5 to 10 mph. Overnight lows will fall to the mid 70s basin wide.
Tributaries to the Highland Lakes, including the upper Colorado River, Llano River, Sandy Creek and Pedernales River, were not impacted by rainfall earlier this week and remain low and steady and lake inflows are minimal.
No releases are scheduled today at Buchanan Dam or Inks Dam. Releases may be made at Wirtz Dam and Starcke Dam to maintain lake levels. Releases from Lake Travis for downstream users will be passed through Lake Austin and Tom Miller Dam. Releases from Lady Bird Lake through Longhorn Dam are controlled by Austin Energy, the electric utility for the City of Austin.
As of 7:19 am, the level of Lake Buchanan was steady at 1011.76 ft msl, which is 1.9 feet below its historic July average of 1,013.64 ft msl. Lake Travis was declining slowly, currently at 672.39 ft msl which is 3.5 feet above its historic July average of 668.84 ft msl. The total combined storage in the Highland Lakes two water storage reservoirs, Buchanan and Travis, is 1,679,000 acre-feet, or 83 percent of capacity. The surface water temperature of Lake Travis measured near Mansfield Dam is 86 degrees.
Downstream from Austin, river flow is ranging from 1,700 cubic feet per second (cfs) near Bastrop to 1,250 cfs at Columbus. Further downstream the flow is 980 cfs near Wharton and 750 cfs at Bay City. The flow at Wharton and Columbus will fall slowly from current levels as runoff from rainfall earlier this week moves downriver past Bay City. To see real-time hydrologic data please go to http://hydromet.lcra.org/.
Unscheduled releases could occur at any of the Highland Lakes dams without notice to maintain lake levels, pass flood flows, meet sudden demands for hydroelectric power, or for testing and maintenance of equipment. In the event of high energy demands in Texas, the Electric Reliability Council of Texas (ERCOT) may call upon LCRA for hydroelectric generation at anytime without notice. Lakeside residents and lake users immediately downstream of the dams should take necessary precautions against possible high flows and higher lake levels.
Elevations contained in this summary are based on LCRA "legacy" or NGVD 29 datum and are not adjusted to the newer NAVD 88 datum. FEMA and the National Flood Insurance Program reference the NAVD 88 datum in their floodplain maps and regulations. Lake levels reported by LCRA should not be used to determine first floor elevation of buildings for compliance with floodplain regulations. Surveyors should refer to http://harn.lcra.org/ for information about LCRA GPS control marks and benchmarks.
Lower Basin Instream and Bay and Estuary Inflow Needs
Each year LCRA releases water for instream flow needs for the Colorado River below Austin, and bay and estuary inflow needs for Matagorda Bay, depending on the combined storage of lakes Buchanan and Travis. The environmental flow needs and lake level triggers are defined in the Water Management Plan for the lower Colorado River Basin. These environmental flows can be met using inflows coming into the river downstream of Mansfield Dam or by releases of water from the Highland Lakes. 2010 is a "target" year for instream flow needs and an "intermediate" year for bay and estuary needs as defined in the Water Management Plan. LCRA is only obligated to meet "target" environmental flow needs to the extent of inflows to the Highland Lakes. However, even in a "target" year, LCRA must maintain critical instream flows regardless of how much inflow enters the Highland Lakes.
Colorado River Instream Flow Needs In a Target Year, the Colorado River instream flow needs are defined by meeting specific minimum flows at four hydromet stations downstream of Longhorn Dam. For those locations, the Target Flow for the current month and Yesterday’s Mean Daily Flow are displayed below:
Instream Flow Conditions
Location
Yesterday's Mean Daily Flow (cfs)
Target Mean Daily Flow (cfs)
Colorado River at Austin
1350
100
Colorado River at Bastrop
1510
370
Colorado River at Columbus
1170
300
Colorado River at Wharton
1070
240
Matagorda Bay and Estuary Freshwater Inflow Needs In an intermediate year, Matagorda Bay inflow needs from the Colorado River are 21,390 acre feet per month.
