One special element of the San Marcos Foothills West Mesa is the perennial spring in the northwest corner that provides the only natural, year-round water source on the entire San Marcos Foothills. The spring was likely used to provide water for cattle during ranching times. At some undetermined point in the past, a long metal pipe was inserted in the hillside at the top of a small arroyo. This pipe apparently converted a natural seep into a controlled stream of water that falls into a bathtub, perhaps placed there at the same time. Water accumulates to as much as 7 to 10 inches in depth, depending on the state of repair of the tub that has cracks in the bottom.