Dry climates are defined by little precipitation.

Annual temperatures of approximately 26 – 34°C. 

The precipitation threshold in millimetres (mm) is determined by multiplying the average annual temperature in Celsius by 20, then adding:

(a) 280 if 70% or more of the total precipitation is in the spring and summer months (April–September in the Northern Hemisphere, or October–March in the Southern), or
(b) 140 if 30%–70% of the total precipitation is received during the spring and summer, or
(c) 0 if less than 30% of the total precipitation is received during the spring and summer.

-    BW = Arid
-    BS = Semi-arid

Arid climate

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Space-based Solution

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Suggested solution

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. 

Data requirements 

  • Rainy season identification 
    Decadal Precipitation in Kenya
    Figure 1: Decadal Precipitation in Kenya. Precipitation information during 21-31 December 2023. (Source: Dekadal Rainfall (meteo.go.ke))


    • Precipitation data from at least the last three years: CHRIPS  
    Decadal rainfall data
    Figure 2: Decadal rainfall in mm from July 2020 to July 2023. (Source: Dekadal Rainfall (meteo.go.ke))


    Precipitation maps 

    samburu precipitation map
    Figure 3: Precipitation map from 2023 made with QGIS. Version 3.32.3 / Version 3.28.11 LTR. The yellow areas indicate heavy rainfall, the green areas indicate moderate rainfall. 


    samburu precipitation map
    Figure 4: Precipitation map from 2024 made with QGIS. Version 3.32.3 / Version 3.28.11 LTR. The yellow areas indicate heavy rainfall, the green areas indicate moderate rainfall.  


    • Digital elevation Model (DEM)
    Samburu DEM map
    Figure 5: Precipitation DEM map made with QGIS. Version 3.32.3 / Version 3.28.11 LTR. 

    Future steps

    • Determine if enough water can be stored during the rainy season to last the dry season.
    Relevant publications
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