3R techniques
- 1. 3R techniques (some examples) Sander de Haas (PWN, SamSamWater Foundation) 31 October 2012, Kajiado, Kenya
- 3. Rainfall in the Kajiado area About 600 mm per year (on average)
- 5. Roof water harvesting • 0,6 m3 per m2 • Roof: 5 x 6 = 30 m2 • 18 m3 per year = 18,000 litres per year = 49 litre per day = 5 buckets per day
- 6. Roof water harvesting Advantages •Available near the house •Possible (almost) everywhere Disadvantages •Small volume •Relatively expensive (per litre) •Regular maintenance required How to identify? •Suitable roof area (type + size) •Determine demand (domestic or more) •Calculate required tank size based on demand + availability
- 9. Rock catchment • Rock catchment: 200 m x 200 m x 0,6 m = 24,000 m3 = 24,000,000 litre per year = 66,000 litre per day
- 10. Rock catchment Advantages •Large volume •Low investment •Good quality Disadvantages •Storage required •Need suitable location How to identify? •Suitable slope •(semi) impervious •Check during rains! •Calculate amount of water
- 11. . .
- 12. Catchment • River catchment: 2000 m x 2000 m x 0,6 m = 2,400,000 m3 = 2,400,000,000 litre per year = 6,600,000 litre per day Combine 3R techniques to retain a part of this water!
- 13. Road catchment
- 14. Road catchment Advantages • Large catchment area -> a lot of water • Reduces road erosion • Cheap Disadvantages • Poor water quality (oil leakage?) • Losses by evaporation How to identify? • Check for runoff traces • Make use of existing structures / depressions
- 15. Recharge ponds
- 16. Recharge ponds
- 17. Recharge pond Advantages • Water quality increased by filtration • Infiltration reduces evaporation Disadvantages • Need suitable geology • Not all water might be recovered • Shallow groundwater table needed How to identify? • Permeable soil • Shallow groundwater available after rainy season
- 18. Sand dams
- 19. Sand dams / subsurface dams Advantages • Sand acts as a natural filter • No evaporation, no mosquitoes • Relatively low cost (per litre) Disadvantages • Need suitable geology (sandy riverbed, impervious bedrock) • Risk of dam breach or erosion along sides How to identify? • Check for sand in riverbed • Check for groundwater in sand several time after the rains
- 21. Flood water diversion Advantages • A lot of water available • Might reduce flash-flood problems downstream Disadvantages • Large surface area needed • Risk of damage (houses, crops) when diverting flood water How to identify? • Check for suitable (flat) areas to divert the water to • Determine if flooding could cause problems (siltation, water damage, etc.)
- 22. Spring protection Advantages • Increases water quality Disadvantages • Might have to find a solution for watering the animals How to identify? • Every spring deserves protection! • Identify potential risks for water quality (latrines, fertilisers, pesticides, cattle feaces, playing children, etc.) • Think of most suitable method (spring head protection, runoff diversion, spring catchment protection, etc.) to reduce these risks.
- 23. Do you have any suggestions? Advantages • ... Disadvantages • ... How to identify? • ...
- 24. Case study: Elangata Wuas Think of these (and other) options when we are in the field. Which options might be suitable for this site? How can we determine the possibilities in the field tomorrow? Can we estimate the potentially available amount? And how does this fit with the demand (domestic, animals)?
- 25. Conclusion No single ‘magical’ 3R technique Use most suitable techniques for the site Combine techniques to increase water availability and benefit from each other Make use of the natural landscape and existing structures