Colorado River not expected to exceed flood stage at locations downstream of Austin

Be sure to check the Situation Report for the very latest info on dam operations and lake and river forecasts.

AUSTIN – The lower Colorado River is expected to remain below flood stage at all locations downstream of Austin as LCRA continues to manage the deluge of runoff following the torrential Hill Country storms that brought up to 19 inches of rain on June 27. However, with rain still in the forecast, conditions could change quickly.

At 2 p.m. Tuesday, July 3, the lower Colorado River was below flood stage at all locations, though six locations downstream of the Highland Lakes exceeded bank-full stage: the Colorado River at Austin below Longhorn Dam, Bastrop, Smithville, La Grange, Wharton and Bay City.

LCRA officials are closely watching today's rainy conditions in Texas coastal areas. With the lower Colorado River system full, significant amounts of rain downstream of Austin could cause the river to exceed flood stage in some locations. All of LCRA’s lake forecasts take into account only the rain that already has fallen and do not include any additional rainfall.

Peak flows and flow times
It takes nearly a week for floodwaters to work their way down the basin from Lake Travis and into the Gulf of Mexico.

Currently, LCRA has four of 24 floodgates open at Mansfield Dam, which forms Lake Travis. Lake Travis is designed specifically to contain floodwaters until the water can be released downstream. While floodgate operations are forecast to continue for several weeks, LCRA will not open any more floodgates at Mansfield Dam unless Lake Travis is forecast to rise above 710 feet above mean sea level (msl) based on rainfall already having fallen. This is because LCRA operates Lake Travis under U.S. Army Corps of Engineers' rules that consider both forecasted lake levels and river levels at key locations downstream.

Specifically, under its operating rules, LCRA must consider three control points downstream of Lake Travis before it can release more water -- at Austin, Bastrop and Columbus. At Lake Travis' currrent elevation of about 700 feet msl, LCRA must consider the river’s current level at these locations:

Austin: The control point is a stage of 20.5 feet at the gauge near the U.S. 183 bridge. At 2 p.m., the river's stage was at that limit.
Bastrop: The limit is a stage of 25.1 feet. At 2 p.m., the Bastrop river gauge showed a stage of 20.55 feet. (Visitors can view a reading for the Bastrop's gauge in person by going to the park area on the east side of the Bastrop bridge.)
Columbus: The control point is 35.5 feet. At 2 p.m., the river Columbus was at 29.7 feet — far below the limit. You can check the stage and streamflow levels yourself on the situation report.

These control points are just one of the many variables LCRA dam operators take into consideration as part of a balancing act to carefully release floodwaters and at the same time limit possible flooding. Rainfall along the Gulf Coast today would not impact the releases from Lake Travis.

Dangerous, murky water
With swift currents and debris floating downstream, emergency management officials warn people to avoid recreational activities in the river for their safety and the safety of rescue personnel.

Moreover, flooding conditions have impacted water quality throughout the lower Colorado River basin, according recent water quality testing by LCRA scientists. Water quality conditions in Bastrop, Smithville, La Grange, Columbus, Wharton and Bay City all rated as “poor” because of a surge of sediments, bacteria and debris washed into streams and lakes.

LCRA reminds people of the hazards associated with boating or swimming in water that has received runoff from heavy rains. Be aware that swimming in natural water bodies increases your risk of illness caused by bacteria. Bacteria levels typically return to normal in about a week to 10 days after the peak runoff.

Drivers — as well as walkers — should not attempt to travel through water that is causing flooding at low-water crossings. Travelers are urged to follow the advice of the National Weather Service's campaign about the hazards of walking or driving through flood waters: Turn Around Don't Drown™.