María José Molina-Montero
Geographer at FAB-LAB at Inter-American Institute for Cooperation on Agriculture
Why is the approach suggested
Rainwater harvesting is a crucial solution for water scarcity in semi-arid countries like Kenya. Kenya’s arid and semi-arid lands (ASALs) cover 80% of its territory, making rainwater harvesting essential. There are various reasons why this approach can be beneficial in Samburu County.
- Water Scarcity Mitigation: Semi-arid regions face unpredictable rainfall and frequent droughts, exacerbated by climate change. Rainwater harvesting captures the little rainfall received, providing a reliable water source.
- Sustainable Water Supply: Rainwater harvesting techniques include small planting basins, trenches, stone bunds, and grass strips. These structures redirect runoff towards crops and pastures. By capturing rainwater, communities can sustain livestock, crop production, and domestic needs.
- Environmental Resilience: Droughts in Kenya are becoming more frequent due to environmental degradation and climate change. Rainwater harvesting helps mitigate the impact of these droughts.
- Cost-Effective and Low-Tech: Rainwater harvesting doesn’t require complex infrastructure. It utilizes existing resources effectively.
- Site Selection: Identify suitable locations for rainwater harvesting. Consider factors such as rainfall patterns, topography, and proximity to communities. Choose areas with consistent rainfall during specific seasons.
- Catchment Area: Determine the catchment area where rainwater will be collected. Common catchment surfaces include rooftops, roads, or open fields. Ensure that the catchment area is clean and free from contaminants.
- Conveyance System: Design an efficient system to channel rainwater from the catchment area to storage facilities. Components include gutters, downspouts, pipes, and first-flush diverters. Proper sizing and maintenance are crucial.
- Storage Tanks or Reservoirs: Select appropriate storage options based on community needs. Common choices include:
- Roof catchment tanks: Placed near buildings to store rainwater from rooftops.
- Ground-level tanks: Buried or partially buried to store larger volumes.
- Rock catchments: Natural depressions or excavated pits lined with impermeable materials.
- Consider tank capacity, material durability, and accessibility for maintenance.
- Water Quality and Treatment: Rainwater may contain impurities. Implement filtration systems to improve water quality. Use first-flush diverters to discard initial runoff (which may contain debris).
- Climate Resilience: Adapt the project to changing climate conditions. Monitor rainfall patterns and adjust storage capacity accordingly.
- Rainy season identification
- Precipitation data from at least the last three years: CHRIPS
- Digital elevation Model (DEM)
- Map available rainfall with CHIRPS with Kenya Space Agency data
- Determine if enough water can be stored during the rainy season to last the dry season
- Combine with meteorological data (SPI values)
- NDVI and DEM to get seasonality of the water cycle