The Lower Colorado River Authority (LCRA) is set to open two floodgates at the Mansfield Dam on Saturday, marking the first such action since 2019. This decision follows substantial rainfall in the Hill Country, which has brought Lake Travis to the top of its conservation pool.
The Mansfield Dam is a key component of a series of dams along the Colorado River that collectively create the Highland Lakes system. Lake Travis, formed by the dam, serves not only as a water supply reservoir for Austin and surrounding areas but also plays a crucial role in flood control by managing stormwater through controlled releases.
Currently, the LCRA can only operate the floodgates at the Mansfield Dam if the water releases do not excessively elevate river levels downstream. However, should Lake Travis continue to rise, the authority will be able to release larger quantities of water with fewer restrictions regarding downstream conditions.
The first floodgate is expected to open at approximately 6 a.m. on Saturday, with the second following around 1 p.m., according to LCRA officials. In preparation for this, a floodgate at the Tom Miller Dam, located downstream of Mansfield, will open on Friday to accommodate the expected influx of water.
Additionally, floodgates at both the Wirtz Dam and the Starcke Dam, situated further upstream on the Colorado River, were opened yesterday and will remain operational.
While the opening of floodgates at the Mansfield Dam is an unusual event, it does not indicate an imminent risk of the reservoir lacking the capacity to manage floodwaters. The reservoir is designed with an additional capacity known as a “flood pool,” which exceeds the amount reserved for regular water supply—referred to as the “conservation pool.”
The flood pool at Lake Travis can accommodate an impressive additional 776,062 acre-feet of water, which is equivalent to more than one hundred Lady Bird Lakes. John Hofmann, the LCRA’s executive vice president for water, noted that the flood storage capacity is nearly on par with the reservoir’s water supply storage.
Nonetheless, the increase in water flow downstream may create complications, prompting the LCRA to advise that currents will be swift and water levels elevated below the dams.
This situation is ongoing and will be updated as more information becomes available.
