Presentation on theme: "SWITCH Training Kit: Pilot Training, Entebbe, 28-29 July 2010 Water Demand Management in the City of the Future Alternative sources of supply - Rainwater."— Presentation transcript:
SWITCH Training Kit: Pilot Training, Entebbe, 28-29 July 2010 Water Demand Management in the City of the Future Alternative sources of supply - Rainwater harvesting
Potential for potable water substitution – Use of the water quality cascade
When is rainwater catchment appropriate? when there is a suitable rainfall pattern when it is affordable compared to alternatives when other water sources are:- onot readily available or inconveniently located oof poorer quality ounreliable when it is wanted by the householder especially for uses that require low quality water – toilet flushing, garden watering Page 3
Catchments and uses roofs of buildings oHouses – outdoor uses, indoor uses oOffices, hotels etc - use for toilet flushing New hotels in Beijing, China Others – especially for outdoor uses oNatural, improved, artificial surfaces Harvesting rainfall reduces drainage requirements Page 4
Is a rainwater catchment system technically feasible? CALCULATE:- oDEMAND total demand during the longest period when there is no rain, or only very little rain oSUPPLY total volume captured by roof in whole year oSTORAGE REQUIRED the minimum volume of storage required at any time during the whole year Page 5
Contamination of harvested rainwater Sources of contamination oatmosphere ocatchment surface and gutters oduring storage and collection oin the home oduring maintenance Contamination is not a problem for uses that require low quality water Page 6
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