Less than a mile upriver the San Marcos doesn’t exist. It comes springing up out of the ground all at once in one of the largest springs anywhere. By the time it gets to Rio Vista the water is still incredibly clear and surprisingly cold. It runs at about the same rate all year every year. It is not slowed much by drought or boued much by rain.
The history of Rio Vista is interesting. Like many spots on Texas rivers a short dam used to be here. The dam generated no electricity and generally served no purpose other than to make the river above it a little slower and a little wider. Like many of these short dams this one over the years had grown structurally unsound. The city of San Marcos was deciding if they should replace it before it fell down on its own or just tear it down. A group of kayakers had other plans. They lobbied to replace the dam with a series of three drops, each progressively smaller than the first. They added artificial boulders to create nice currents know as eddies. Soon after opening they actually held Olympic trials qualifier runs at the site, complete with slalom gates. It didn’t take long however before tubers decided it was lots of fun to go over at the end of the Lions club tubing shuttle. Locals also like going over it without a tube and swimming in the whitewater current despite the danger of swift water. Soon the swimmers took over the warmer months and whitewater kayers were relegated to using Rio Vista at night when it is lit up by flood lights and during the cooler months when swimmers trade in their bathing suits for textbooks.