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Rainwater harvesting: Sizing and modeling (view source)
Revision as of 13:50, 17 August 2017
, 6 years ago→Simple
*''R<sub>a</sub>'' = The average annual rainfall depth (mm)
*''R<sub>a</sub>'' = The average annual rainfall depth (mm)
*''e'' = The efficiency of the pre-storage filter}}
*''e'' = The efficiency of the pre-storage filter}}
Filter efficiency (e) can be reasonably estimated as 0.9 pending manufacturer’s information.<br>
*Filter efficiency (e) can be reasonably estimated as 0.9 pending manufacturer’s information.<br>
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 a number of overflow events.
*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 a number of overflow events.
#The average annual demand (D) is greater than the average annual yield (Y) from the catchment.
#The average annual demand (D) is greater than the average annual yield (Y) from the catchment.
When \(0.33<Y_{0.05}/D_{0.05}<0.7\), the storage volume required can be estimated:
When \(Y_{0.05}/D_{0.05}<0.33\), the storage volume required can be estimated:
<math>V_{S} = A \times C_{vol,E}\times R_{d} \times e</math>
<math>V_{S} = A \times C_{vol,E}\times R_{d} \times e</math>
Where:
Where:
*''e'' = The efficiency of the pre-storage filter.}}
*''e'' = The efficiency of the pre-storage filter.}}
\*Careful catchment selection means that the runoff coefficient, for a rainstorm event (C<sub>vol, E</sub>) should be 0.9 or greater.
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>:
When \(0.33<Y_{0.05}/D_{0.05}<0.7\), the total storage required can be estimated by adding Y<sub>0.05</sub>:
<br>
<br>
<strong>Total storage = V<sub>S</sub> + Y<sub>0.05</sub></strong>
<math>TotalStorage = V_{S} + Y_{0.05}</math>
===STEP Rainwater Harvesting Tool===
===STEP Rainwater Harvesting Tool===