There are two important questions that need to be asked in the construction of open earth tanks. Why not dams, and how do you decide where to build an open earth tank?
Tanks are not dams. Dams are a construction where by you blocks an existing waterway and tanks are an excavation into which water is diverted. Because tanks only collect a small amount of the water that goes through the waterway, controlling the excess is a vital factor. This is done by the way of constructing earth banks to divert the water initially and then constructing a “bywash bank” which ends on higher ground to allow the tank to fill and the excess water to return to the natural water-way. Unlike a dam that can effect the ecology above it’s trapping point as well as the flow below, the open earth tank does neither of these things and is only used for one purpose. That purpose is to maintain the livestock’s need for water during the dry season.
Due to the huge flow of water during the “wet” dams could not control the water that flows down to the plains nor is there a need for the farmers to try. Tanks remain the most effective way for farmers to water their live stock with out being to intrusive to the natural environment around them.
The second question is how you decide just where to build an open earth tank. The first requirement is to select a strategic area on the station, which is deficient in water for the stock to be able to make use of the natural vegetation. The next requirement is to find a waterway that is sufficient to fill your tank. Sometimes these waterways can be surprisingly small. Next an open flat area is required to accommodate the excavation which can use up to a two acres. Then the trick is to construct the tank in a spot that it will fill easily and the water is not to hard to control.
The open earth tank provides livestock with life maintaining water through the “dry” season in an environmentally non-intrusive way.
John