1. Rain Water Harvesting

2. Why Harvest Rain Water Reduce ground water demand Storage allows anytime use Reduce flash-floods Reduce erosion Naturally clean Naturally soft Sustainable Low Cost

3. Suitable if conservation already maxed-out terrain is rugged or mountainous water is too hard or mineral laden lack of water security (potentially) electricity & water prices are rising groundwater is scarce (potentially) population density is low (The Gambia) seismic & flooding events are common groundwater is contaminated (potentially) consumers must restrict salt/chlorine intake where availability is unreliable (The Gambia) the aquifer is at risk of saltwater intrusion (potentially)

4. Uses – Non-potable Agriculture –Livestock –Crops –Gardens Cleaning –Laundry –Dishes –Bathing

5. Natural Solar Distillation

6. Simplest System Catchment area

7. Simple System Catchment area Distribution

8. Typical System Catchment area Screens Conveyance system Roof washer Storage Distribution

9. Complex System Catchment area Screens Conveyance system Roof washer Storage Purification Distribution

10. Catchment area Largest existing structures Non-organic roofs Metal corrosion Cost - none

11. Conveyance system Gutters or Water-tight fabrics Fasteners / brackets Screens Cost - low

12. Roof washer Diverts first flush –By volume – easiest –By rate - problematic Availability Cost - low

13. Storage Cistern –Concrete –Metal –Plastic For dry season Cost - highest

14. Sizing Cistern –0.62 gallons / ft^2 (footprint) / inch (rain) –75% - 90% efficiency –Use median rainfall data –Establish need Diversion Tank –Divert 10 to 50 gallons / 1000 ft^2 Level of pollution

15. Questions?