Rain Water Harvesting
Why Harvest Rain Water Reduce ground water demand Storage allows anytime use Reduce flash-floods Reduce erosion Naturally clean Naturally soft Sustainable Low Cost
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)
Uses – Non-potable Agriculture –Livestock –Crops –Gardens Cleaning –Laundry –Dishes –Bathing
Natural Solar Distillation
Simplest System Catchment area
Simple System Catchment area Distribution
Typical System Catchment area Screens Conveyance system Roof washer Storage Distribution
Complex System Catchment area Screens Conveyance system Roof washer Storage Purification Distribution
Catchment area Largest existing structures Non-organic roofs Metal corrosion Cost - none
Conveyance system Gutters or Water-tight fabrics Fasteners / brackets Screens Cost - low
Roof washer Diverts first flush –By volume – easiest –By rate - problematic Availability Cost - low
Storage Cistern –Concrete –Metal –Plastic For dry season Cost - highest
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
Questions?