Thursday’s overnight rains should result in a rise of about a foot or two on Lake Travis by the end of this weekend, while the elevation of Lake Buchanan should remain relatively unchanged, according to LCRA projections.

As of 8 a.m. Friday, Lake Travis had risen almost three-quarters of a foot from the overnight rains, which have not required LCRA to go into flood operations along the Highland Lakes chain of dams.

But LCRA cautions residents along the lakes, Colorado River and tributaries to pay attention to weather conditions, as Friday’s forecast calls for a 40 percent chance of rain for the region. With much of the region already saturated, any additional rains could easily turn into dangerous runoff.

Rains of 1 to 3 inches fell overnight Thursday across the upper basin, with rains of 4 to 5 inches near Harper. The storm generated substantial runoff into the Llano River, which flows into Lake LBJ. LCRA is passing along the runoff into Lake Travis through its hydroelectric power stations at Wirtz and Starcke dams.

The runoff will result in Lake Travis rising slightly from its 6 a.m. Friday elevation of 639.18 feet above mean sea level (msl) to an expected range of 640-641 feet msl by late Sunday.

Much of Thursday night’s rains were concentrated in the Lake Travis watershed and are not expected to have a significant effect on the elevation of Lake Buchanan, which had a 6 a.m. Friday elevation of 997.04 feet msl.

For more information check the LCRA River Report for a summary of lake and river conditions and LCRA’s Hydromet for real-time lake levels and streamflows.