Siphakeme .Mnindwa
Judith Phiri, Business Reporter
FARMERS have been urged to explore different rain water harvesting strategies that will aid them to improve productivity.
Water harvesting involves collecting and storing rainwater or runoff for future use, while it enables farmers to utilise rainwater efficiently, reduce soil erosion, and ensure consistent water supply for crops, even during dry spells.
According to Agribusiness Media, the primary methods of water harvesting include contour bunds, micro-catchments, rooftop harvesting, and more, each suited to different terrains and farming needs.
It said: “Water is a critical resource for agriculture, yet its availability is increasingly threatened by climate change and erratic rainfall patterns. To address these challenges, water harvesting has emerged as a vital solution, allowing farmers to optimise water use, increase crop yields, and enhance resilience.”
Agribusiness Media said contour bunds are ridges constructed along the natural contours of a slope and they work by slowing down runoff, allowing water to infiltrate the soil.
It said this method is ideal for areas with gentle to moderate slopes and degraded soils, while the steps for constructing contour bunds include surveying the land to identify contour lines using tools like the A-frame and marking the contour lines with sticks or stones.
“One should also build small ridges along these lines using soil, stones, or plant residues. Advantages of this method include prevents soil erosion, enhanced groundwater recharge and improved crop yields on sloping lands.
On micro-catchments, Agribusiness Media said these are small, strategically designed basins that capture and store runoff water directly where it is needed.
It said they are particularly effective in arid and semi-arid regions for growing trees, shrubs, and crops.
“Types of micro-catchments include semi-circular bunds: commonly used for fruit trees, contour ridges: ideal for annual crops and trapezoidal bunds: designed for larger areas. Key considerations for micro-catchments is to ensure the basins are aligned to capture maximum runoff and maintain the structures regularly to prevent siltation.”
Agribusiness Media said rooftop water harvesting is a simple yet effective method where rainwater is collected from rooftops and stored in tanks.
It said this system is particularly useful for domestic purposes and small-scale irrigation of high-value horticultural crops.
“How it works, rainwater is directed from sloping roofs into plastic gutters, the water flows through a downpipe into a storage tank and the tank should be covered with a tarpaulin or black plastic to prevent algae growth and mosquito breeding,” added Agribusiness Media.
It said its advantages include low labour and maintenance requirements, suitable for areas with limited space and provides clean water for irrigation and household use.
However, Agribusiness Media said its challenges are ground-level tanks may require a pump for irrigation when water levels are low and raised tanks offer better pressure but involve higher construction costs.
On using the a-frame for contour marking, it said an A-frame was a simple tool made of three pieces of wood joined in an “A” shape, with a weighted string hanging from the top.
“It helps farmers mark contours on slopes for various water harvesting techniques. Steps for contour marking include placing one foot of the A-frame at a field boundary, swinging the other leg until the string hangs in the middle, indicating the contour and marking the position of the other foot and repeat the process to map out the contour line.”
Agribusiness Media said measuring gradients is done by calibrating the A-frame by testing it on ramps with known slopes and marking gradient measurements directly on the A-frame for quick reference.
