Because of its volume, the lake serves as the primary flood control reservoir of the Highland Lake chain. The level of the lake can therefore vary dramatically, depending on the amount of rainfall in the Colorado River basin upstream. Despite this, the lake furnishes one of the most desired locations in the region for outdoor recreation, including fishing, boating, swimming, scuba diving, picnicking, camping, and zip lining. Another recreational use, nude sunbathing and swimming, is permitted in Hippie Hollow Park. This picturesque park is located near the eastern end of Lake Travis and holds the distinction of being the only legal clothing optional park in Texas. Lake Travis is generally considered one of the clearest lakes in Texas. It is a vital water supply for the nearby city of Austin, Texas and the surrounding metropolitan area.
In spring 2008 there were several reports of leeches residing in Lake Travis. The leeches are generally harmless to humans but can be a nuisance.
Lake Travis is considered "full" (at maximum desired capacity) when the lake's water level is at 681 feet (208 m) above mean sea level (msl). Above 681 feet (208 m), flood control gates are opened under the direction of the U.S. Army Corps of Engineers. The historic high level on the lake was 710.4 feet (216.5 m) above msl on December 25, 1991. The historic low was 614.2 feet (187.2 m) above msl on August 14, 1951. The extreme drought of 2008-2009 brought the lake to its fourth lowest level at 626.09 feet (190.83 m) above msl in November 2009. The second lowest level was 615.02 feet (187.46 m) above msl on November 8, 1963. Due to the 2010–13 Southern United States drought, levels have gone as low as 618 feet, making it the third lowest level ever. The LCRA makes reports of lake levels available on the internet.
^The lake rose to 642.39 feet above msl as of October 25, 2009 due to significant rains in September and October 2009. This places the level at 24 feet below normal level for October. "River Report" LCRA.