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Low-cost water harvesting techniques

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According to the Agroforestry World, Kenya is a water-scarce country with less than 600 cubic meters per capita below the global 1000 cubic meters per capita. Water scarcity is a critical constraint to the country’s socio-economic development.

This situation is exacerbated by climate change and increasing water demand due to population growth and urbanization.

To respond to the water scarcity and inadequate distribution, new techniques need to be explored and old techniques revisited. Small–scale water harvesting techniques provide a direct solution, especially in rural and drought-prone areas hence the use of water harvesting techniques.

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In urban areas dam construction, long-distance conveyance of water or desalinization may provide options for ensuring water availability. These solutions are generally too costly and complicated for rural water security. Rural populations require low-cost systems that can be constructed, operated, and maintained with the highest level of community involvement and autonomy.

Fog Harvesting

Fog harvesting is another technique. It is captured with the help of polypropylene mesh nets or ridges to capture water-loaded fog that forms in humid months in mountainous or coastal areas. The mesh normally collects small water droplets which trickle into collection troughs, gutters, and drains into a series of tanks. Fog harvesting is cheap and the level of technology and maintenance is simple, furthermore, the technique is easy to replicate.

Sand Dams

Another example is sand dams made by Kitui farmers through Sahelian Solutions (SASOL)– a Non-Governmental Organization. They constructed 500 sand dams serving more than 150,000 people. The dams are placed across a bed of intermittent small rivers, consisting of a 1.5 to 2-meter-high impermeable barrier from stone or concrete placed on a firm impermeable layer of rock or clay. These rocks prevent water from going back to the ocean. Runoff water is stopped from flowing and will create an artificial aquifer that can store up to 35% of its total volume as groundwater.

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Contour Trenching

This involves digging trenches along contour lines. Water flowing down the hill is retained by the trench, and it infiltrates the soil below. A good example is in Amboseli dug by Westerveld Conservation Trust. When they dug the trenches they chose deep and closely spaced trenches 4 meters and a meter deep at 25 meter intervals down the slope high enough to capture rain of up to 150mm per day.

In between two dug-up trenches, crops can be grown and benefit when there’s less rain from the subsoil water reserve gathered after the rainy season.

Finger ponds

Finger ponds are an innovative technique that is used to enhance the natural productivity of wetlands and floodplains. The ponds may consist of stretched artificial ponds 5 to 12 meters long, extending to the wetlands like fingers hence the name.
These ponds normally fill up during the flood cycle and trap fish within them as the floods recede. Some of the advantages are that the environmental impact of finger ponds in terms of habitat destruction, nutrient leaching, and disease vectors was established to be generally low.

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Grey water

Grey water should be another rich target. Grey water is the wastewater from baths, showers, washing machines, dishwashers, and sinks and this water normally makes up 50-80 per cent of household waste. (the Greenage UK). If properly recycled properly, greywater can save approximately 70 liters of portable water per person per day in domestic households. Greywater cannot be used for drinking but can be used for flushing toilets, washing clothes, and even watering your garden.

Advantages of rainwater harvesting
  • RWH is a quick solution, to increase the availability of water, in areas that have inadequate resources.
  • It increases groundwater levels and mitigates the effects of drought.
  • It reduces rainwater run-off, which may otherwise, flood stormwater drains.
  • It serves as a cost-effective method to reduce soil erosion.

Photo Credit: Sand-dams dug by Kitui people through Sahelian Solutions (SASOL), a Non-Governmental Organization.

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