The nobility of a humble weir.
Nothing beats seeing an erosion ditch silting up. Allow me to elaborate.
Annually, South Africa loses 12.6 tonnes of valuable topsoil from every one of the country’s hectares. This is three times higher than Australia.
At the risk of depressing the reader further, one should also bear in mind that it takes Mother Nature at least 500 years to generate one inch of this life-giving resource.
Topsoil is life-giving because the very existence of humanity depends on it. We grow our food and flowers in it; it sustains animal and livestock grazing and protects the soil’s water-holding capacity.
Conversely, soil erosion silts up dams and lessens the ground’s biomass resulting in poor water filtration and infiltration. Erosion also terribly scars the countryside like giant wounds bleeding into the ocean.
The soil loss mainly happens due to poor pasture management, overgrazing, and incorrect and overzealous tillage practices. Additionally, large parts of South Africa have meagre rainfall and sparse vegetation, making the country enormously susceptible to erosion.
As temporary custodians of the land and first responders, farmers have the moral obligation to leave their farms in a healthier state than when they received them. Improvements in grazing and tillage methods are clearly vital; however, a humble little weir can do wonders.
Years ago, I toiled on a farm in the Karoo. The land suffered the area’s typical erosion ditches due to its hilly topography and sparse flora. The Department of Agriculture was still at pains to teach farmers the subtle art of erosion control. Over time, it bore fruit when the district showed remarkable recovery.
The methods we utilised were mostly simple and, notably, cheap. Tyre weir construction was one.
The method involves digging opposing insertion gaps into the side walls of a gulley. Old car tyres are stacked flat and on top of each other, wall-to-wall, forming a curved barrier perpendicular to the water’s flow.
Next, the tyres are filled with rocks and tied together with number eight galvanised wire. Typically, a series of these barriers are required to reclaim a long ditch. It is advisable to anchor the weir upstream in deep gullies with metal poles and wire.
The way nature responds to these contraptions is simply astounding. The gully silts up on the upstream side, conserving the soil and allowing standing water to generate a tiny ecosystem. Ultimately, opportunistic species of grass eagerly reclaim the ditch. Nature is so grateful.