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| ===Rapid=== | | ===Rapid=== |
| <p>Five percent of the average annual yield can be estimated:<br> | | <p>Five percent of the average annual yield can be estimated: |
| <strong>Y<sub>0.05</sub>= A × C<sub>vol</sub> × R<sub>a</sub> × e × 0.05</strong> | | <br><strong>Y<sub>0.05</sub>= A × C<sub>vol, A</sub> × R<sub>a</sub> × e × 0.05</strong> |
| <br>Y<sub>0.05</sub> = Five percent of the average annual yield (L) | | <br>Y<sub>0.05</sub> = Five percent of the average annual yield (L) |
| <br>A = The catchment area ( m<sup>2</sup>) | | <br>A = The catchment area ( m<sup>2</sup>) |
| <br>C<sub>vol</sub> = The runoff coefficient for the catchment | | <br>C<sub>vol, A</sub> = The annual runoff coefficient for the catchment |
| <br>R<sub>a</sub> = The average annual rainfall depth (mm) | | <br>R<sub>a</sub> = The average annual rainfall depth (mm) |
| <br>e = The efficiency of the pre-storage filter | | <br>e = The efficiency of the pre-storage filter |
| | <ul> |
| | <li>Filter efficiency (e) can be reasonably estimated as 0.9 pending manufacturer’s information. </li> |
| | <li>In a study of three sites in Ontario, STEP found the annual C<sub>vol, A</sub> of the rooftops to be around 0.8 [http://www.sustainabletechnologies.ca/wp/home/urban-runoff-green-infrastructure/low-impact-development/rainwater-harvesting/performance-evaluation-of-rainwater-harvesting-systems-toronto-ontario/]. This figure includes losses to evaporation, snow being blown off the roof, and number of overflow events.</li> |
| | </ul> |
| | </p> |
| | <p>Five percent of the average annual demand (D<sub>0.05</sub>) can be estimated: |
| | <br><strong>D<sub>0.05</sub> = P<sub>d</sub> × n × 18.25</strong> |
| | <br>D<sub>0.05</sub> = Five percent of the average annual demand (L) |
| | <br>P<sub>d</sub> = The daily demand per person (L) |
| | <br>n = The number of occupants |
| </p> | | </p> |
| <p>Five percent of the average annual demand (D<sub>0.05</sub>) can be estimated:<br>
| |
| <strong>D<sub>0.05</sub> = P<sub>d</sub> × n × 18.25</strong>
| |
| <br>D<sub>0.05</sub> = Five percent of the average annual demand (L)
| |
| <br>P<sub>d</sub> = The daily demand per person (L)
| |
| <br>n = The number of occupants
| |
| <br>Good catchment selection means that the runoff coefficient (C<sub>vol</sub>) should be 0.9 or greater. Filter efficiency (e) can be reasonably estimated as 0.9 pending manufacturer’s information.</p>
| |
| ---- | | ---- |
| <p>Then the following calculations are based upon two criteria: | | <p>Then the following calculations are based upon two criteria: |
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| </ol> | | </ol> |
| </p> | | </p> |
| <p>When Y<sub>0.05</sub>/ D<sub>0.05</sub> < 0.33, the storage volume required (V<sub>S</sub>, in L) can be estimated:<br> | | <p>When Y<sub>0.05</sub>/ D<sub>0.05</sub> < 0.33, the storage volume required can be estimated: |
| <strong>V<sub>S</sub> = A × C<sub>vol</sub> × R<sub>d</sub> × e</strong><br> | | <br><strong>V<sub>S</sub> = A × C<sub>vol</sub> × R<sub>d</sub> × e</strong> |
| <br>V<sub>S</sub> = Storage volume required (L) | | <br>V<sub>S</sub> = Storage volume required (L) |
| <br>A = The catchment area (m<sup>2</sup>) | | <br>A = The catchment area (m<sup>2</sup>) |
| <br>C<sub>vol</sub> = The design storm runoff coefficient for the catchment | | <br>C<sub>vol, E</sub> = The design storm runoff coefficient for the catchment |
| <br>R<sub>d</sub> = The design storm rainfall depth (mm), and | | <br>R<sub>d</sub> = The design storm rainfall depth (mm), and |
| <br>e = The efficiency of the pre-storage filter. | | <br>e = The efficiency of the pre-storage filter. |
| | <ul> |
| | <li>Good catchment selection means that the runoff coefficient, for a rainstorm event (C<sub>vol, E</sub>) should be 0.9 or greater.</li> |
| | </ul> |
| </p> | | </p> |
| <p>When 0.33 < Y<sub>0.05</sub>/ D<sub>0.05</sub> < 0.7, the total storage required can be estimated by adding Y<sub>0.05</sub>: <br> | | <p>When 0.33 |
| <strong>Total storage = V<sub>S</sub> + Y<sub>0.05</sub></strong> | | < Y<sub>0.05</sub>/ D<sub>0.05</sub> |
| | < 0.7, the total storage required can be estimated by adding Y<sub>0.05</sub>: |
| | <br> |
| | <strong>Total storage = V<sub>S</sub> + Y<sub>0.05</sub></strong> |
| </p> | | </p> |
| ---- | | ---- |
| </div> | | </div> |
| <div class="col-md-4"> | | <div class="col-md-4"> |
| <panelInfo> | | <panelInfo> |
| <gallery mode="packed" widths=300px heights=300px> | | <gallery mode="packed" widths=300px heights=300px> |
| Cistern Size.png| Schematic diagram of the inputs and outputs to a rainwater harvesting cistern | | Cistern Size.png| Schematic diagram of the inputs and outputs to a rainwater harvesting cistern |
| </gallery> | | </gallery> |
| </panelInfo> | | </panelInfo> |
| </div> | | </div> |
| <div class="col-md-12"> | | <div class="col-md-12"> |