Springs occur where the water table within an aquifer meets a valley slope resulting in a slow flow of water emerging from the ground . Most springs occur as a slow, modest trickle of water, but greater discharge volumes do occur where artesian springs flow upwards to the ground surface under pressure, usually resulting in the formation of lakes, wetlands, and streams.
1. Rainwater infiltrates the substrate and moves down into the aquifer.
2. Water cannot pass through impervious rock layers and flows along
on top of them.
3. Where this underground flow connects with the outside surface slope,
it flows out through cracks or faults in the rock to create springs.
4. In some cases the spring may have a constant flow which feeds into
nearby streams and rivers.
Springs are typical of areas with horizontal or near horizontal layers of sedimentary rock and are a typical feature of steep hill and mountain terrain.
Springs are the natural provision of water for livestock and wildlife and although usually only a slow trickle, the flow is often perennial; the actual source being the considerable amount of water that is stored within porous and permeable layers of rock.
The reliability of spring flow depends on the porosity of the subsurface rock or gravel formations and the amount of water that they can absorb varies tremendously. The amount and frequency of rainwater recharge of these porous and permeable substrates will also determine the reliability of spring flow and surface habitat condition plays an important role as well.
Natural springs may be seasonal and when the flow is weak, the underground formation may be damaged or clogged by heavy hoofed animals attempting to get at the water source. Under these conditions, the quantity and permanence of flow can sometimes be increased by protecting the spring source. The principle is to protect the spring with a built cistern cover and to pipe the water away from the source into a waterhole, trough or vlei area where it can be used by thirsty animals.
This is done by digging out the area around the spring source right down to the impervious bedrock layer and to remove all silt, mud, decomposed rock, rock fragments and mineral matter such as calcium carbonate which is sometimes deposited by rising water. Care must be taken to not damage underground formations such as limestone, to the extent that the spring is diverted in another direction.
A watertight cistern is then constructed directly onto the bedrock. The design, shape or materials used are not critical, as long as the structure will effectively protect the spring source (Figure 2). Water can be taken off near to the top of the cistern and gravity-piped to the supply point. It is important that mesic conditions around the spring should not be changed, and this may mean that some of the water must be permitted to overflow to maintain moist conditions for plants and small fauna around the spring. It is not necessary to pipe the water far away from the spring as the objective is merely to protect the water source from damage. The best option is to provide water for wildlife or livestock in a small waterhole or seepage that can overflow to maintain the wet conditions typical of natural springs.
A simple cemented stone or brick enclosure will adequately protect the spring source. An outlet pipe can be used for extraction, another permits normal spring-flow and a third with a screw-on cap is used for draining and cleaning-out the sump.
Springs can also be protected by enclosing them to keep larger animals away from the source. Heavy animals drinking at springs sometimes can clog-up the spring by trampling clay or mud into the fissures that deliver the water. This is easily prevented by fencing off important springs so that thirsty animals can drink from the runoff at a safe distance away from the actual source.
The materials to use for such a barrier should be robust and need only be made from poles and split-pole rails. The objective is to keep larger and heavier animals away so there is no need to completely fence-off the spring against the access of smaller animals.
If the natural drainage substrate is too porous to hold water long enough to provide drinking water for animals, then a simple, stone and cement lined permanent trough can be installed outside of the enclosure with a buried pipe feed from the spring. The trough can overflow, and the excess spring water can seep back into the ground, as it did before.
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