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<li> 0.05 </li></ul></p>Good catchment selection means that the runoff coefficient (C<sub>vol</sub>) should be 0.9 or greater. Filter efficiency can be reasonably estimated as 0.9 pending manufacturer’s information.
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Rainwater harvesting: Sizing and modeling (view source)
Revision as of 19:08, 11 July 2017
, 7 years ago→Rapid
===Rapid===
===Rapid===
<p>Five percent of the average annual yield (Y<sub>0.05</sub>, in L) is calculated as the product of:
<p>Five percent of the average annual yield can be calculated using the following equation:<br>
<ul><li>The catchment area (A, in m<sup>2</sup>)</li>
<strong>Y<sub>0.05</sub>= A × C<sub>vol</sub> × R<sub>a</sub> × e × 0.05</strong>
<li>The runoff coefficient for the catchment (C<sub>vol</sub>)</li>
<ul>
<li>The average annual rainfall depth (R<sub>a</sub>, in mm)</li>
<li>Y<sub>0.05</sub> = Five percent of the average annual yield (L)
<li> the efficiency of the pre-storage filter (e), and </li>
<li>A = The catchment area ( m<sup>2</sup>)</li>
<li>C<sub>vol</sub> = The runoff coefficient for the catchment</li>
<p>Five percent of the average annual demand (D<sub>0.05</sub>) is calculated as the product of:
<li>R<sub>a</sub> = The average annual rainfall depth (mm)</li>
<ul><li> The daily demand per person (P<sub>d</sub>, in L)</li>
<li>e = The efficiency of the pre-storage filter</li>
<li> The number of occupants (n)</li>
</ul>
<li> 365, and </li>
</p>
<li> 0.05 </li></ul></p>
<p>Five percent of the average annual demand (D<sub>0.05</sub>) is calculated as the product of:<br>
<strong>D<sub>0.05</sub> = P<sub>d</sub> × n × 18.25</strong>
<ul>
<li>D<sub>0.05</sub> = Five percent of the average annual demand (L)</li>
<li>P<sub>d</sub> = The daily demand per person (L)</li>
<li>n = The number of occupants</li>
</ul>
Good catchment selection means that the runoff coefficient (C<sub>vol</sub>) should be 0.9 or greater. Filter efficiency can be reasonably estimated as 0.9 pending manufacturer’s information.</p>
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<p>The following calculation is based upon two criteria:
<p>The following calculation is based upon two criteria:
<ol><li>A design rainfall depth is to be captured entirely by the RWH system.</li>
<ol>
<li>The average annual demand (D) is greater than the average annual yield (Y) from the catchment. </li></ol></p>
<li>A design rainfall depth is to be captured entirely by the RWH system.</li>
<p><strong>When Y<sub>0.05</sub>/ D<sub>0.05</sub> <0.33</strong> <br>
<li>The average annual demand (D) is greater than the average annual yield (Y) from the catchment. </li>
The total storage volume required (V<sub>S</sub>, in L) is calculated as the product of:
</ol>
<ul>
</p>
<li>The catchment area (A, in m<sup>2</sup>)</li>
<p><strong>When Y<sub>0.05</sub>/ D<sub>0.05</sub> <0.33</strong>
<li>The design storm runoff coefficient for the catchment (C<sub>vol</sub>)</li>
<br> The total storage volume required (V<sub>S</sub>, in L) is calculated as the product of:
<li>The design storm rainfall depth (R<sub>d</sub>, in mm), and </li>
<ul>
<li> the efficiency of the pre-storage filter (e). </li></ul>
<li>The catchment area (A, in m<sup>2</sup>)</li>
<li>The design storm runoff coefficient for the catchment (C<sub>vol</sub>)</li>
<li>The design storm rainfall depth (R<sub>d</sub>, in mm), and </li>
<li> the efficiency of the pre-storage filter (e). </li>
</ul>
</p>
</p>
<p><strong>When 0.33 < Y<sub>0.05</sub>/ D<sub>0.05</sub> <0.7</strong> <br>
<p><strong>When 0.33 < Y<sub>0.05</sub>/ D<sub>0.05</sub> <0.7</strong>
The total storage required is the sum of V<sub>S</sub> and Y<sub>0.05</sub>. </p>
<br> The total storage required is the sum of V<sub>S</sub> and Y<sub>0.05</sub>. </p>
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