One of the most effective yet often overlooked ways to increase farm productivity and long-term value is to retain and store as much rainwater as possible, whether you farm on 1 000 hectares or a small plot.
By Roelof Bezuidenhout
In South Africa, the average annual rainfall is about 450mm, less than half the global average of about 950mm. This makes rainwater harvesting essential. Even in places with higher rainfall, like parts of KwaZulu-Natal, efficient water management pays off.
Climate patterns are changing. Many areas now experience long dry spells followed by short, heavy downpours. If rainwater is not slowed, stored or absorbed into the soil, much of it is simply lost as runoff.
Water harvesting – both direct (from roofs and hard surfaces) and indirect (from land and catchments) – makes sense when you realise how much water can run off your farm into rivers or the sea, or be taken up by unwanted plants.
By slowing down runoff, you can:
- Improve soil moisture.
- Recharge groundwater and wells.
- Reduce erosion.
- Increase crop and pasture resilience.
- Create more productive and attractive spaces on you farm.
Also read: An affordable dam you can build yourself
Slowing Water, Storing Value
Rainwater can be slowed so that it soaks into topsoil and recharges aquifers (underground water-bearing rock). Water can also be directed into tanks, pits or dams for later use in irrigation, livestock watering or household needs.
A powerful example comes from India, where small-scale farmers use networks of stone-filled recharge pits to improve water supply. These pits are typically about 3m × 3m × 3m, dug by hand or excavator in carefully selected areas. Hundreds of such pits can exist in a relatively small catchment.
Runoff water enters the pits, filters through stones and slowly percolates into the rock below, replenishing wells for dry periods. Because the water is stored underground, it does not evaporate, and erosion is reduced. This method is known as artificial groundwater recharge.
Also read: Your water could be killing productivity – simple water management tricks every farmer needs to know
How Much Water Are We Talking About?
The potential volume of harvestable water is often underestimated:
- A small shed roof measuring 10m × 10m (100m²) can capture up to 50 000 litres per year at 500mm rain. That’s enough to fill 10 standard 5 000-litre tanks.
- One hectare – or 100m × 100m (10 000m²) – of land getting 500mm rain represents 5 million litres – the equivalent of 1 000 of those 5 000-litre tanks.
- Ten hectares could yield 50 million litres in one rainy season.
Of course, actual results depend on soil type, slope, plant cover and infiltration rate. Well-covered soil produces less runoff, but more water infiltrates the soil to nourish veld, crops or pastures. Good ground cover also reduces wind and water erosion.
Hard surfaces such as roofs, concrete paving and tar roads have nearly 100% runoff efficiency – as a rule, 100 litres per 1mm rain per 100m².
Also read: Take good care of your windpump
Anyone Can Do This
Almost anyone with a spade, pick and wheelbarrow can turn part of their land into a productive oasis. Water can make even dry land bloom and can attract birds and wildlife back to a farm.
Water harvesting does not require high-tech systems. Many solutions are affordable and well-suited to low-input homestead gardens, which are vital for food security, especially in communal areas.
Also read: A simple solution to retain rainwater
Storage and Retention Options
For all of the options below, maintenance is essential. Water systems improve with time only if they are maintained and adapted.
- Larger earth dams, common on commercial farms, store significant volumes but may require clay or geomembrane lining to reduce seepage. This can be costly.
- Smaller dams, preferably in series in low-lying areas, capture runoff and gradually line themselves with vegetation. The deeper the dams, the less water is lost to evaporation.
- Rock barriers across small watercourses slow flow and trap sediment. Avoid using old tyres – they release pollutants.
- Small hollows or basins dug into bare ground slow runoff, trap seeds and retain moisture. Over time, vegetation establishes naturally.
- Rooftop harvesting can feed above- or below-ground plastic or concrete tanks.
- To reduce evaporation, cover dams and open tanks with shade netting, corrugated iron sheets or floating aquatic plants. In India, farmers often use bamboo mats.
- Plow along contours to create natural barriers that hold water.
- Protect natural springs using small stone weirs to create reliable water points.
- Remove alien plants and woody invaders. Farmers often report noticeably improved water flow after clearing once good rains return.
Planning Irrigation Wisely
The Department of Water and Sanitation typically uses 5 000m³ (5 million litres) per hectare per year as a benchmark for general irrigation needs. This means a well-managed borehole may support about 2 hectares, depending on crop type and irrigation efficiency.
Weigh up the pros and cons of flood irrigation, overhead irrigation and drip irrigation to decide what best suits your soil, crops and budget.
Always factor in the local climate, and use planning tools such as SAPWAT (a locally designed software program for estimating irrigation water requirements) to refine water-use estimates and improve drought resilience.
The Water Research Commission offers a wealth of practical, farmer-friendly information.
Don’t just watch water flow down the road – capture it, store it and let it work for you.
Also read:
Proposed stricter borehole rules could affect farmers
Hollows that trap water and seeds aid in veld restoration
 | Roelof Bezuidenhout is a fourth-generation wool, mohair, mutton and game farmer and freelance journalist. Attended Free State University, majoring in animal husbandry and pasture science. Other interests include agricultural extension and rural development. |
