Managing Semi-Arid Watersheds: Watershed Basics - Stock Tanks

As you travel through Arizona's cattle country and National Forests you may have noticed stock tanks or small earthen ponds scattered across these lands. Their primary purpose is to provide water for grazing livestock and wildlife animals. Have you ever noticed where they are located on the landscape? These structures are not built randomly. They are specifically designed to harvest runoff water and store it for animal use. The location is carefully chosen to maximize this function. Usually they are constructed using a bulldozer that scoops out a shallow basin in the path of seasonal runoff water. The earth is pushed downslope of the basin to form a barrier or retaining wall. As water flows downslope, it collects in these earthen basins until they are full. The average water depth in these stock tanks is usually no more than 3 or 4 feet, however, in years of low rainfall, these stock tanks can dry up.

So, who builds these tanks? Usually it is the livestock producer. Stock tanks play a crucial role in enabling livestock to graze remote areas because animals must have a water supply and it is cost prohibitive to haul water to them by truck. The construction of stock tanks, especially on public lands, has benefitted many wildlife species because they have access to these additional water sources too. Next time you see a stock tank, notice where it is on the landscape and try to figure out where the water that is in it comes from.