3R techniques (some examples)

Sander de Haas (PWN, SamSamWater Foundation)31 October 2012, Kajiado, Kenya

www.samsamwater.com/climate

Rainfall in the Kajiado area

About 600 mm per year (on average)

Roof water harvesting

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

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

Rock catchment

Rock catchment

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

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

.

.

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!

Road catchment

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

Recharge ponds

Recharge ponds

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

Sand dams

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

Flood water diversion

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.)

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.

Do you have any suggestions?

Advantages• ...

Disadvantages• ...

How to identify?• ...

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)?

Conclusion

No single ‘magical’ 3R technique

Use most suitable techniques for the siteCombine techniques to increase water availability and benefit from each other

Make use of the natural landscape and existing structures