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→Performance
|Yes-size for water quality storage requirement
|Yes-size for water quality storage requirement
|Partial-based on available storage volume and if a flow restrictor is used
|Partial-based on available storage volume and if a flow restrictor is used
|}
===Water Balance===
Recent research indicates that a conservative runoff reduction rate of 10 to 20% can be used depending on whether soils fall in hydrologic soil groups A/B or C/D, respectively. The runoff reduction rates can be doubled if the native soils on which the swale is located have been tilled to a depth of 300 mm and amended with compost to achieve an organic content of between 8 and 15% by weight or 30 to 40% by volume. The mai ncontributing factors that influence runoff reduction rates for swales are:
* Native [[Soil groups|soil]] types
* [[Grading|Slope]]
* [[Vegetation|Vegetative cover]] and,
* [[Enhanced swales: Specifications|Length of the swale.]]
{|class="wikitable"
|+Volumetric runoff reduction from enhanced swales
|-
!'''LID Practice'''
!'''Location'''
!'''<u><span title="Note: Runoff reduction estimates are based on differences between runoff volume from the practice and total precipitation over the period of monitoring unless otherwise stated." >Runoff Reduction*</span></u>'''
!'''Reference'''
|-
|rowspan="4" style="text-align: center;" | Grass Swale
|style="text-align: center;" |Virginia
|style="text-align: center;" |0%
|style="text-align: center;" |Schueler (1983)<ref>Schueler, T. 1983. Washington Area Nationwide Urban Runoff Project. Final Report. Metropolitan Washington Council of Governments. Washington, DC. </ref>
|-
|style="text-align: center;" |Various Locations
|style="text-align: center;" |40%
|style="text-align: center;" |Strecker et al.(2004)<ref>Strecker, E., Quigley, M., Urbonas, B., Jones, J. 2004. State-of-the-art in comprehensive approaches to stormwater. The Water Report. Issue 6. August 15,2004. </ref>
|-
|style="text-align: center;" |France
|style="text-align: center;" |27-41%
|style="text-align: center;" |Barrett ''et al''. (2004)<ref>Barrett, M.E. 2008. Comparison of BMP Performance Using the International BMP Database. Journal of Irrigation and Drainage Engineering. September/October. pp. 556-561.</ref>
|-
|style="text-align: center;" |Washington
|style="text-align: center;" |97 to 100%
|style="text-align: center;" |Brattebo and Booth (2003)<ref name="example2">Brattebo, B. and D. Booth. 2003. Long term stormwater quantity and quality
performance of permeable pavement systems. Water Research 37(18): 4369-4376 </ref>
|-
| colspan="2" style="text-align: center;" |'''<u><span title="Note:This estimate is provided only for the purpose of initial screening of LID practices suitable for achieving stormwater management objectives and targets. Performance of individual facilities will vary depending on site specific contexts and facility design parameters and should be estimated as part of the design process and submitted with other documentation for review by the approval authority" >Runoff Reduction Estimate*</span></u>'''
|colspan="2" style="text-align: center;" |'''20% on [[Soil groups|HSG A or B soils]];'''
'''10% on [[Soil groups|HSG C or D soils]]'''
|-
|}
|}
==References==
==References==