SWITCH Training Kit: Pilot Training, Entebbe, 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