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→Calculating infiltration practice drainage time
[[File:Interevent times.PNG|thumb|link=https://public.tableau.com/views/StormIntereventTimesOntario/Dashboard1?:embed=y&:display_count=yes&publish=yes|Darker teal locations have more frequent rainfall; darker yellow have the least frequent rainfall. This image links to a Tableau dashboard, where the interactive data may be viewed in more detail.]]
<iframe src="http://myserver/views/Date-Time/DateCalcs?:embed=yes&:toolbar=no"
The recommended drawdown times for all storage and [[infiltration]] facilities ([[infiltration trenches|trenches]], [[infiltration chambers|chambers]], [[bioretention]] etc.) are based upon rainfall statistics and likelihood that the facility will have had time to regenerate storage capacity before the arrival of the next storm event.
A summary analysis of 14 locations across Ontario found that storms were most frequent in Thunder Bay and least frequent in Toronto; there is a ~50% chance of rainfall occurring again within 48 hours (Thunder Bay) to 72 hours (Toronto).
The analysis was conducted using the recommended minimum inter-event time of 12 hours from the MOECC<ref>Aquafor Beech, EarthFX. Runoff Volume Control Targets for Ontario Final Report. 2016:125. http://www.downloads.ene.gov.on.ca/envision/env_reg/er/documents/2017/012-9080_Runoff.pdf. Accessed September 11, 2017.</ref>, and earlier rainfall probability distribution parameters from 1960's-1980's <ref>Adams, B. J., and Papa, F. (2000). Urban stormwater management planning with analytical probabilistic models. Wiley.</ref>.
It is not anticipated that recent incremental changes to our climate will have significantly impacted this broad window of recommended drainage times.
Locations considered included:
<div style="column-count:3;-moz-column-count:3;-webkit-column-count:3">
*Brantford
*Etobicoke
*Hamilton
*Kingston
*London
*Niagara Falls
*Oshawa
*Ottawa
*Peterborough
*Sault Ste Marie
*Thunder Bay
*Toronto
*Trenton
*Windsor
</div>
==Calculating infiltration practice drainage time==
Try the Darcy drainage time calculator tool for estimating the time required to fully drain the water storage reservoir of the facility assuming either one or three-dimensional drainage: <br>
{{Clickable button|[[Media:Darcy drainage_20200528_locked.xlsx|Download the Darcy drainage time calculator tool]]}}
==See also==
[[Understanding rainfall statistics]]
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[[Category:Infiltration]]
[[Category: Background]]