Rainwater harvesting: Sizing and modeling

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Rapid[edit]

Total cistern volume can be estimated by multiplying the depth of design storm the catchment area. 1 mm of rain over 1 m2 results in 1 L of runoff. For example, the 90th percentile event in Barrie is 26 mm, so every 1 m2 of rooftop will generate 26 L during this storm event. A 2000 m2 building would generate 54,000 L of runoff. The designers have three choices:-

  1. Construct a suitably sized concrete vault underground to capture all of the water
  2. Alter the slope of the roof to create two or more catchments, the smaller catchments may be diverted to plastic or fiberglass cisterns
  3. Design 1. or 2. Slightly undersized for this storm, but with additional capacity in an infiltration system to capture overflow. Examples include bioretention cells or infiltration chambers.

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STEP Rainwater Harvesting Tool[edit]

The Sustainable Technologies Evaluation Program have produced a rainwater harvesting design and costing tool specific to Ontario. The tool is in a simple to use Excel format and is free to download.

<panelWarning> STEP Rainwater Harvesting Tool </panelWarning>


The Treatment Train Tool[edit]

Once the size of cistern has been determined, it can easily be modelled in many open source and proprietary applications.

In addition to the cistern size, modelling requires

<btnPrimary>The Treatment Train Tool</btnPrimary>


See Also[edit]

This list will be other 'Sizing and Modelling' pages


External Links[edit]


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