his may be new knowledge for those new to Texas. The San Antonio Riverwalk is drained every two years, and it is currently empty. If you want to see this Texas phenomenon, you have till Monday, January 19, which is when the riverwalk is set to be filled and back to normal. The San Antonio Riverwalk is drained biannually for routine maintenance and cleaning. If you’ve ever visited the riverwalk, you know it can get pretty dirty. And when it’s drained, it’s kind of gross to see all the mud and grime that lurks beneath…