Changes

[[File:Geothermal cooling exchange system.PNG|thumb|700px|A simplified 3D cross section of a geothermal cooling system used in a SWM pond in Brampton, Ontario. The system contains a closed hydronic circuit where piping connected a surface water heat exchanger (SHX) to a ground heat exchanger (GHX). A pump continuously circulates a cool hydronic fluid around the circuit. The SHX (placed in the path of the pond outflow) has the water pass through it. The hydronic fluid circulating through the SHX is cooler than warm stormwater outflows. This temperature difference forces heat energy from the stormwater into the hydronic fluid, thus cooling the stormwater leaving the pond. Read more about the system [https://www.chijournal.org/C483 Here]. Photo Source: (Janssen and Van Seters,2022.)<ref>Janssen, E. and Van Seters, T. 2022. Thermal Mitigation of Stormwater Management Pond Outflows Using Geothermal Cooling. Journal of Water Management Modeling. https://www.chijournal.org/Content/Files/C483.pdf</ref>]]

[[File:Geothermal cooling exchange system.PNG|thumb|660px|A simplified 3D cross section of a geothermal cooling system used in a SWM pond in Brampton, Ontario. The system contains a closed hydronic circuit where piping connected a surface water heat exchanger (SHX) to a ground heat exchanger (GHX). A pump continuously circulates a cool hydronic fluid around the circuit. The SHX (placed in the path of the pond outflow) has the water pass through it. The hydronic fluid circulating through the SHX is cooler than warm stormwater outflows. This temperature difference forces heat energy from the stormwater into the hydronic fluid, thus cooling the stormwater leaving the pond. Read more about the system [https://www.chijournal.org/C483 Here]. Photo Source: (Janssen and Van Seters,2022.)<ref name="example1">Janssen, E. and Van Seters, T. 2022. Thermal Mitigation of Stormwater Management Pond Outflows Using Geothermal Cooling. Journal of Water Management Modeling. https://www.chijournal.org/Content/Files/C483.pdf</ref>]]

{{TOClimit|limit=3}}

{{TOClimit|limit=3}}

*''C'' = heat capacity of water (4187J/kg°C)}}  

*''C'' = heat capacity of water (4187J/kg°C)}}  

Since urban runoff volumes often increase by 2 to 5 times after development, and stormwater pond effluent temperatures are between 4 and 11°C warmer than pond influent temperatures in the summer, the overall thermal load increases to streams can be very significant ([https://sustainabletechnologies.ca/app/uploads/2019/04/Thermal-Synthesis-Final.pdf Van Seters and Dougherty, 2019]).<ref>Van Seters, T., and Dougherty, J. 2019. Data Synthesis and Design Considerations for Stormwater Thermal Mitigation Measures. Sustainable Technologies Evaluation Program. Ontario. https://sustainabletechnologies.ca/app/uploads/2019/04/Thermal-Synthesis-Final.pdf</ref>

Since urban runoff volumes often increase by 2 to 5 times after development, and stormwater pond effluent temperatures are between 4 and 11°C warmer than pond influent temperatures in the summer, the overall thermal load increases to streams can be very significant ([https://sustainabletechnologies.ca/app/uploads/2019/04/Thermal-Synthesis-Final.pdf Van Seters and Dougherty, 2019]).<ref name="example2">Van Seters, T., and Dougherty, J. 2019. Data Synthesis and Design Considerations for Stormwater Thermal Mitigation Measures. Sustainable Technologies Evaluation Program. Ontario. https://sustainabletechnologies.ca/app/uploads/2019/04/Thermal-Synthesis-Final.pdf</ref>

==Selecting a Stream Temperature Target==

==Selecting a Stream Temperature Target==

===Upstream of the Pond===

===Upstream of the Pond===

Any measure that decreases runoff volumes or temperatures or both can help mitigate thermal loads to streams or downstream treatment facilities.  Examples include [[bioretention]], [[infiltration trenches]] or [[infiltration chambers|chambers]], [[enhanced swales]], [[permeable pavements]], [[rain gardens|absorbent landscaping]] and increased canopy cover.  The figures below show the temperature (event mean temperature) and thermal load reduction results from several LID practices monitored in the Greater Toronto Area (Van Seters and Dougherty, 2019).<ref>Van Seters, T., and Dougherty, J. 2019. Data Synthesis and Design Considerations for Stormwater Thermal Mitigation Measures. Sustainable Technologies Evaluation Program. Ontario. https://sustainabletechnologies.ca/app/uploads/2019/04/Thermal-Synthesis-Final.pdf</ref>]] The most effective practices were deeper systems such as trenches, some deep bioretention facilities, and practices that promote significant runoff volume reductions. Beyond reducing temperatures and runoff volumes, enhancing [[infiltration]] also helps re-establish the natural baseflow regime that existed prior to development.<br>

Any measure that decreases runoff volumes or temperatures or both can help mitigate thermal loads to streams or downstream treatment facilities.  Examples include [[bioretention]], [[infiltration trenches]] or [[infiltration chambers|chambers]], [[enhanced swales]], [[permeable pavements]], [[rain gardens|absorbent landscaping]] and increased canopy cover.  The figures below show the temperature (event mean temperature) and thermal load reduction results from several LID practices monitored in the Greater Toronto Area (Van Seters and Dougherty, 2019).<ref name="example2" /> The most effective practices were deeper systems such as trenches, some deep bioretention facilities, and practices that promote significant runoff volume reductions. Beyond reducing temperatures and runoff volumes, enhancing [[infiltration]] also helps re-establish the natural baseflow regime that existed prior to development.<br>

<br>

</br>

</br>

[[File:STEP MONITORING.jpg|thumb|450px|Example of TRCA/STEP staff conducting monitoring tasks associated with a bioretention cell at Kortright Centre in Vaughan, ON. Staff are downloading water level data from the feature using a [[Digital technologies|data logger]] placed within a monitoring well.<ref>TRCA. 2017. Furthering the State of Knowledge on Stormwater Management - News. October 4th, 2017. Accessed: April 18th, 2022. https://trca.ca/news/furthering-the-state-of-knowledge-on-stormwater-management/</ref>]]

[[File:STEP MONITORING.jpg|thumb|500px|Example of TRCA/STEP staff conducting monitoring tasks associated with a bioretention cell at Kortright Centre in Vaughan, ON. Staff are downloading water level data from the feature using a [[Digital technologies|data logger]] placed within a monitoring well.<ref>TRCA. 2017. Furthering the State of Knowledge on Stormwater Management - News. October 4th, 2017. Accessed: April 18th, 2022. https://trca.ca/news/furthering-the-state-of-knowledge-on-stormwater-management/</ref>]]

===Within the Pond Block===

===Within the Pond Block===

[[File:Subsurface draw outlet.PNG|500px|thumb|Schematic of a reverse sloped subsurface draw outlet to help ensure cooler outflows occur from stormwater ponds (MOE, 2003).<ref>Ministry of the Environment. 2003. Stormwater Management Planning and Design Manual. March, 2003. ISBN 0-7794-2969-9. PIBS 4329e. https://dr6j45jk9xcmk.cloudfront.net/documents/1757/195-stormwater-planning-and-design-en.pdf</ref>]]

[[File:Subsurface draw outlet.PNG|500px|thumb|Schematic of a reverse sloped subsurface draw outlet to help ensure cooler outflows occur from stormwater ponds (MOE, 2003).<ref>Ministry of the Environment. 2003. Stormwater Management Planning and Design Manual. March, 2003. ISBN 0-7794-2969-9. PIBS 4329e. https://dr6j45jk9xcmk.cloudfront.net/documents/1757/195-stormwater-planning-and-design-en.pdf</ref>]]

There are several opportunities to mitigate thermal impacts both within the pond itself and/or implemented within the upstream drainage area (and the lands surrounding) of the pond.  Options shown in past studies to provide appreciable thermal mitigation benefits include (Van Seters and Dougherty, 2019).<ref>Van Seters, T., and Dougherty, J. 2019. Data Synthesis and Design Considerations for Stormwater Thermal Mitigation Measures. Sustainable Technologies Evaluation Program. Ontario. https://sustainabletechnologies.ca/app/uploads/2019/04/Thermal-Synthesis-Final.pdf</ref><br>

There are several opportunities to mitigate thermal impacts both within the pond itself and/or implemented within the upstream drainage area (and the lands surrounding) of the pond.  Options shown in past studies to provide appreciable thermal mitigation benefits include (Van Seters and Dougherty, 2019)<ref name="example2" />.<br>

</br>

</br>

====Night Time Release Outlets====

====Night Time Release Outlets====

Employs real time control on pond outlets to automatically close outlets during the day when surface outflow from ponds is warmer, and release water during the night when outflow temperatures are cooler.  The outlets are configured and programmed to maintain release rates below threshold values for stream erosion prevention and match pre-development peak flow rates.

Employs real time control on pond outlets to automatically close outlets during the day when surface outflow from ponds is warmer, and release water during the night when outflow temperatures are cooler.  The outlets are configured and programmed to maintain release rates below threshold values for stream erosion prevention and match pre-development peak flow rates.

[[File:Temp. depth pond.png|600px|thumb|The graph depicts a depth profile of temperatures in a Southern Ontario pond during the two hottest months of the year (July and August). Depths are in meters below the normal water level.  Note strong diurnal fluctuations at the 0 m , 0.5 m and to a lesser extent at the 1.0 m depths.]]

[[File:Temp. depth pond.png|600px|thumb|The graph depicts a depth profile of temperatures in a Southern Ontario pond during the two hottest months of the year (July and August, where temperature of the pond is heavily influenced by solar radiation during the summer months). Depths are in meters below the normal water level.  Note strong diurnal fluctuations at the 0 m , 0.5 m and to a lesser extent at the 1.0 m depths.]]

'''Design Considerations'''

'''Design Considerations'''

*Optimal 8 hour duration for night time release outlets was found to be between 3 AM and 10 AM inclusive based on data from 4 ponds  

*Optimal 8 hour duration for night time release outlets was found to be between 3 AM and 10 AM inclusive based on data from 4 ponds  

*Optimal 4 hour duration release times were found to be between 6 and 9 AM inclusive (Van Seters and Dougherty, 2019).<ref>Van Seters, T., and Dougherty, J. 2019. Data Synthesis and Design Considerations for Stormwater Thermal Mitigation Measures. Sustainable Technologies Evaluation Program. Ontario. https://sustainabletechnologies.ca/app/uploads/2019/04/Thermal-Synthesis-Final.pdf</ref>]].

*Optimal 4 hour duration release times were found to be between 6 and 9 AM inclusive (Van Seters and Dougherty, 2019)<ref name="example2" />.

*Robust automation technology is critical to avoid excessive repairs and down time.  

*Robust automation technology is critical to avoid excessive repairs and down time.  

*Electrical supply and back-up power are typically needed at the outlet to reduce operation and maintenance requirements

*Electrical supply and back-up power are typically needed at the outlet to reduce operation and maintenance requirements

===='''Cooling Trenches'''====

===='''Cooling Trenches'''====

Cooling trenches typically consist of one or more geotextile wrapped perforated pipes embedded in a clear stone filled trench that is buried underground.  Water temperatures are reduced through heat transfer from the water passing through the trench to the stone and surrounding soils.  Cooling trenches may be installed downstream of the primary pond outlet or draw from a secondary orifice controlled outlet draining water from the pond at or below the permanent pool water level (e.g Van Seters and Graham, 2013<ref> Van Seters, T., Graham, C. 2013. Evaluation of an Innovative Technique for Augmenting Stream Baseflows and Mitigating the Thermal Impacts of Stormwater Ponds. Sustainable Technologies Evaluation Program, Toronto and Region Conservation Authority, Toronto, Ontario. https://sustainabletechnologies.ca/app/uploads/2013/08/Cooling-trench-final-2013a.pdf</ref>.; TRCA, 2020<ref>Toronto and Region Conservation Authority (TRCA) 2020. Evaluation of a Thermal Mitigation System on the Heritage at Victoria Square Pond in Markham. Toronto and Region Conservation Authority, Vaughan, Ontario. https://sustainabletechnologies.ca/app/uploads/2021/01/TM-Heritage-report-2021R.pdf</ref>). Further information about these innovative cooling trench features installed as part of the stormwater pond

[https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/thermal-mitigation/thermal-mitigation-system-evaluation/ Cooling trenches] typically consist of one or more geotextile wrapped perforated pipes embedded in a clear stone filled trench that is buried underground.  Water temperatures are reduced through heat transfer from the water passing through the trench to the stone and surrounding soils.  Cooling trenches may be installed downstream of the primary pond outlet or draw from a secondary orifice controlled outlet draining water from the pond at or below the permanent pool water level (e.g Van Seters and Graham, 2013<ref name="example3"> Van Seters, T., Graham, C. 2013. Evaluation of an Innovative Technique for Augmenting Stream Baseflows and Mitigating the Thermal Impacts of Stormwater Ponds. Sustainable Technologies Evaluation Program, Toronto and Region Conservation Authority, Toronto, Ontario. https://sustainabletechnologies.ca/app/uploads/2013/08/Cooling-trench-final-2013a.pdf</ref>.; TRCA, 2020<ref>Toronto and Region Conservation Authority (TRCA) 2020. Evaluation of a Thermal Mitigation System on the Heritage at Victoria Square Pond in Markham. Toronto and Region Conservation Authority, Vaughan, Ontario. https://sustainabletechnologies.ca/app/uploads/2021/01/TM-Heritage-report-2021R.pdf</ref>). Further information about these innovative cooling trench features installed as part of the stormwater pond

operation design in two sites located in Markham, ON. visit the [https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/thermal-mitigation/thermal-mitigation-system-evaluation/ STEP project page]. The permanent pool of stormwater management ponds acts as a heat sink during the summer, resulting in warmer summer discharges during both storm and baseflow conditions.  

operation design in two sites located in Markham, ON. visit the [https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/thermal-mitigation/thermal-mitigation-system-evaluation/ STEP project page]. The permanent pool of stormwater management ponds acts as a heat sink during the summer, resulting in warmer summer discharges during both storm and baseflow conditions.  

[[File:Cooling Trenches.jpg|450px|thumb|Close up view of a 'cooling trench'. These trenches work by outflows of warm pond water coming into contact with cooler [[stone]]

[[File:Cooling Trenches.jpg|450px|thumb|Close up view of a 'cooling trench'. These trenches work by outflows of warm pond water coming into contact with cooler [[stone]]

media (along the top of the trench) and side walls, which in turn promotes heat transfer between the two, resulting in a reduction in outflow water temperatures beign discharged to a receiving waterbody (i.e., stream) (Van Seters and Dougherty, 2019).<ref> Van Seters, T., and Dougherty J. 2019. Data Synthesis and Design Considerations for Stormwater Thermal Mitigation Measures. Sustainable Technologies Evaluation Program. Ontario. https://sustainabletechnologies.ca/app/uploads/2019/04/Thermal-Synthesis-Final.pdf</ref>. Photo Source: [[Acknowledgements|Azimuth Environmental​]]]]

media (along the top of the trench) and side walls, which in turn promotes heat transfer between the two, resulting in a reduction in outflow water temperatures beign discharged to a receiving waterbody (i.e., stream) (Van Seters and Dougherty, 2019) <ref name="example2" />. Photo Source: [[Acknowledgements|Azimuth Environmental​]]]]

'''Design Considerations'''

'''Design Considerations'''

*Secondary pond outlets that drain water from 0.5 m below the permanent pool elevation to cooling trenches can help to reduce or eliminate the long duration and very warm interevent flows.  

*Secondary pond outlets that drain water from 0.5 m below the permanent pool elevation to cooling trenches can help to reduce or eliminate the long duration and very warm interevent flows.  

*Trenches may incorporate an infiltration function to help further reduce thermal loads if native soils and groundwater levels are suitable.   

*Trenches may incorporate an infiltration function to help further reduce thermal loads if native soils and groundwater levels are suitable.   

 

'''Expected Performance'''

'''Expected Performance'''

*Performance of primary outlet cooling trenches is highly variable due to differences in cooling trench sizing, design, initial water temperature and degree of groundwater interaction   

*Performance of primary outlet cooling trenches is highly variable due to differences in cooling trench sizing, design, initial water temperature and degree of groundwater interaction   

*Based on case studies reviewed, primary outlet trenches without groundwater interaction may provide summer temperature cooling of the warmest flows by roughly 1 to 3⁰C if the trench storage volume is equal to or greater than 5% of the runoff volume discharged from the pond during the 25 mm event.<br>

*Based on case studies reviewed, primary outlet trenches without groundwater interaction may provide summer temperature cooling of the warmest flows by roughly 1 to 3⁰C if the trench storage volume is equal to or greater than 5% of the runoff volume discharged from the pond during the 25 mm event.

</br>

 

[[File:Cooling Trenches excavated.jpg|450px|thumb|Another image of a cooling trench being built with two parallel trenches that contain [[Choker layer|pea gravel]] and two sets of 200 mm perforated [[pipes]] wrapped in filter fabric. (Van Seters and Graham, 2013<ref name="example3" />. Photo Source: [[Acknowledgements|Doug McGill]]]]

===='''Infiltration Systems'''====

===='''Infiltration Systems'''====

The volumes infiltrated may also be used to meet site water balance requirements.  Proponents will need to consult with local approval agencies to determine whether the typical 1 meter separation depth to groundwater may be waived given that the infiltrated water has been treated through the pond.   

The volumes infiltrated may also be used to meet site water balance requirements.  Proponents will need to consult with local approval agencies to determine whether the typical 1 meter separation depth to groundwater may be waived given that the infiltrated water has been treated through the pond.   

Analysis of temperature and thermal load data from three monitored ponds showed that the bottom area of the infiltration area would need to be up to 7% that of the pond area depending on the infiltration capacity of the native soils.  These areas could be reduced by 40% if the outlet draws water from 0.25 m below the surface, and further reduced for deeper outlets (Van Seters and Dougherty, 2019).<ref>Van Seters, T., and Dougherty, J. 2019. Data Synthesis and Design Considerations for Stormwater Thermal Mitigation Measures. Sustainable Technologies Evaluation Program. Ontario. https://sustainabletechnologies.ca/app/uploads/2019/04/Thermal-Synthesis-Final.pdf</ref>]].  

Analysis of temperature and thermal load data from three monitored ponds showed that the bottom area of the infiltration area would need to be up to 7% that of the pond area depending on the infiltration capacity of the native soils.  These areas could be reduced by 40% if the outlet draws water from 0.25 m below the surface, and further reduced for deeper outlets (Van Seters and Dougherty, 2019)<ref name="example2" />.  

{| class="wikitable" style="width: 1000px;"

{| class="wikitable" style="width: 700px;"

|+'''Native Soil Infiltration Rate'''

|+'''Native Soil Infiltration Rate'''

|-

|-

|0.8%

|0.8%

|-

|-

|colspan="4" style="text-align: left;" |'''<u><span title=>Note:''' ''Infiltration system footprint needed to provide pond outflow thermal load reduction benefits equivalent to a 2m bottom draw outlet (expressed as a percent of pond area)''.</span></u>

|colspan="4" style="text-align: left;" |<small>'''<span title=>Note:''' ''Infiltration system footprint needed to provide pond outflow thermal load reduction benefits equivalent to a 2m bottom draw outlet (expressed as a percent of pond area)''.</span></small>

|-

|-

|}<br>

|}

===='''Geothermal Cooling'''====

===='''Geothermal Cooling'''====

This innovative approach uses one or more deep (180 m) geothermal boreholes connected in a closed loop with a pond heat exchanger to cool outflows from stormwater ponds.  A metal or polyethylene heat exchanger is installed in an enclosure at the outlet of the pond.  A heat transfer fluid is pumped through the closed loop to maximize transfer of heat energy from the warm water to the much colder ground.  Warm outflows from the pond enter the enclosure and pass over the pond heat exchanger, which transfers energy from the water to the closed loop and into the ground. The approach was piloted by TRCA/STEP, in partnership with the City of Brampton, on a small pond in Brampton (Janssen and Van Seters, 2021<ref>Erik Janssen and Tim Van Seters. 2021. Geothermal-based Thermal Mitigation of Stormwater Retention Pond Outflows: Report Addendum. Sustainable Technologies Evaluation Program, Toronto and Region Conservation Authority, Vaughan, Ontario. https://sustainabletechnologies.ca/app/uploads/2022/03/Geo_Cooling_Report_2021.pdf</ref> and 2022<ref>Janssen, E. and Van Seters, T., 2022. Thermal Mitigation of Stormwater Management Pond Outflows Using Geothermal Cooling. Journal of Water Management Modeling.https://www.chijournal.org/C483</ref>)  

This innovative approach uses one or more deep (180 m) geothermal boreholes connected in a closed loop with a pond heat exchanger to cool outflows from stormwater ponds.  A metal or polyethylene heat exchanger is installed in an enclosure at the outlet of the pond.  A heat transfer fluid is pumped through the closed loop to maximize transfer of heat energy from the warm water to the much colder ground.  Warm outflows from the pond enter the enclosure and pass over the pond heat exchanger, which transfers energy from the water to the closed loop and into the ground. The approach was piloted by TRCA/STEP, in partnership with the City of Brampton, on a small pond in Brampton (Janssen and Van Seters, 2021<ref>Erik Janssen and Tim Van Seters. 2021. Geothermal-based Thermal Mitigation of Stormwater Retention Pond Outflows: Report Addendum. Sustainable Technologies Evaluation Program, Toronto and Region Conservation Authority, Vaughan, Ontario. https://sustainabletechnologies.ca/app/uploads/2022/03/Geo_Cooling_Report_2021.pdf</ref> and 2022<ref name="example1" />)  

As part of the initiative an online sizing tool for geothermal systems was develop - you can view it by click the button below:

{{textbox|As part of the initiative an online sizing tool for geothermal systems was develop - you can view it by click the button below:

{{Clickable button|[[File:Sizing calculator.PNG|370 px|link=http://geothermal-thermal-mitigation2.herokuapp.com/simplecalc]]}}

{{Clickable button|[[File:Sizing calculator.PNG|370 px|link=http://geothermal-thermal-mitigation2.herokuapp.com/simplecalc]]}}}}

[[File:Borehole drilling.jpg|thumb|500px|Borehole drilling for the City of Brampton thermal mitigation pilot project. (Photo: [[Acknowledgements|TRCA, 2020]])]]<br>

[[File:Borehole drilling.jpg|thumb|500px|Borehole drilling for the City of Brampton thermal mitigation pilot project. (Photo: [[Acknowledgements|TRCA, 2020]])]]

'''Design Considerations'''

'''Design Considerations'''

*The pump used to circulate the heat transfer fluid through the ground loop may be powered by an electrical connection or solar panels.  Larger systems may need designated electrical connections.

*The pump used to circulate the heat transfer fluid through the ground loop may be powered by an electrical connection or solar panels.  Larger systems may need designated electrical connections.

*Initial investigations suggest that systems can be sized based on the average pond outflow rate over a given year to achieve defined temperature thresholds most of the time.   

*Initial investigations suggest that systems can be sized based on the average pond outflow rate over a given year to achieve defined temperature thresholds most of the time.   

 

'''Expected Performance'''

'''Expected Performance'''

Geothermal Cooling works best with subsurface draw outlets (1.2 m or deeper) that provide cooling of the higher flows and would be less expensive than installing additional boreholes (at least in new builds).  When sized appropriately, geothermal systems can shave a few degrees off of the average pond outflow temperature.<br>

Geothermal Cooling works best with subsurface draw outlets (1.2 m or deeper) that provide cooling of the higher flows and would be less expensive than installing additional boreholes (at least in new builds).  When sized appropriately, geothermal systems can shave a few degrees off of the average pond outflow temperature.<br>

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</br>

[[File:Geothermal system configuration.png|600px]]<br>

[[File:Geothermal system configuration.png|700px|center]]<br>

</br>

</br>

See above an example of a geothermal system configuration showing the surface heat exchanger (SHX) in the vault and the borehole ground heat exchanger (GHX). An inexpensive pump circulates heat transfer fluid through the closed loop continuously.<br>

See above an example of a geothermal system configuration showing the surface heat exchanger (SHX) in the vault and the borehole ground heat exchanger (GHX). An inexpensive pump circulates heat transfer fluid through the closed loop continuously.<br>

===='''Other Options'''====

===='''Other Options'''====

Vegetated channels installed downstream of pond outlets can help to reduce temperatures through shading, although typically a long channel is needed to have an appreciable benefit on temperatures.   

Vegetated channels installed downstream of pond outlets can help to reduce temperatures through shading, although typically a long channel is needed to have an appreciable benefit on temperatures.   

Underground detention chambers, have the potential to cool inflowing runoff and maintain temperatures suitable for discharge to cool water fisheries (Drake et al, 2015)<ref>McIntosh, N., Drake, J., Young, D. and Spencer, J. 2015. Modeling Sedimentation in Underground Stormwater Detention Chamber Systems. In International Low Impact Development Conference 2015: LID: It Works in All Climates and Soils (pp. 43-52). https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/low-impact-development/soakaways-infiltration-trenches-and-chambers/evaluation-of-an-underground-stormwater-detention-chamber-system-in-markham-ontario/</ref>

Underground detention chambers, have the potential to cool inflowing runoff and maintain temperatures suitable for discharge to cool water fisheries (Drake et al, 2015)<ref>McIntosh, N., Drake, J., Young, D. and Spencer, J. 2015. Modeling Sedimentation in Underground Stormwater Detention Chamber Systems. In International Low Impact Development Conference 2015: LID: It Works in All Climates and Soils (pp. 43-52). https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/low-impact-development/soakaways-infiltration-trenches-and-chambers/evaluation-of-an-underground-stormwater-detention-chamber-system-in-markham-ontario/</ref>

Surface cover also has the potential to provide cooling benefits. Options include floating islands, solar panels, shade balls, trellis infrastructure to support vines and south shading of east west oriented ponds with trees.  The data from various studies shows that surface cover needs to cover more than 70% of the pond with an opaque surface material to promote appreciable temperature reduction benefits.  Trees on the banks of ponds will not provide immediate thermal benefits as they will take time to grow, but are otherwise an excellent long term strategy.   

Surface cover also has the potential to provide cooling benefits. Options include floating islands, solar panels, shade balls, trellis infrastructure to support vines and south shading of east west oriented ponds with trees.  The data from various studies shows that surface cover needs to cover more than 70% of the pond with an opaque surface material to promote appreciable temperature reduction benefits.  Trees on the banks of ponds will not provide immediate thermal benefits as they will take time to grow, but are otherwise an excellent long term strategy.   

Ponds with large length to width ratios, oriented east-west with shading on the south side can also provide shading, although it will take several years for the shade to become established.<br>

Ponds with large length to width ratios, oriented east-west with shading on the south side can also provide shading, although it will take several years for the shade to become established.

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<gallery mode="packed-hover" perrow=2 widths=250px heights=250px>

[[File:Shade balls close up.jpg|300px]]<br>

File:Shade balls brampton.jpg|An example of an alternative option for thermal mitigation - White shade balls. These specialized balls were used to cover this pond as part of a thermal mitigation pilot project in the City of Brampton. Photo Source: TRCA, 2020. To read more about this novel option for thermal mitigation, click here: [https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/thermal-mitigation/evaluation-shade-balls-mitigating-summer-heating-stormwater-management-ponds Shade Balls study]<ref name="example5">Rocha, L., and VanSeters, T.2020. Evaluation of shade balls for mitigating summer heating of stormwater management ponds. Toronto and Region Conservation Authority, Vaughan, Ontario. https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/thermal-mitigation/evaluation-shade-balls-mitigating-summer-heating-stormwater-management-ponds/</ref>

 

Photo Source: TRCA, 2020. A close up of white<br>

File:Shade balls close up.jpg|A close up of white shade balls used in Esker Pond as part of a thermal mitigation pilot. An example of an alternative option for thermal mitigation. To read more click here: [https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/thermal-mitigation/evaluation-shade-balls-mitigating-summer-heating-stormwater-management-ponds Shade Balls study]<ref name="example5" />  

shade balls used in Esker Pond as part of a<br>

</gallery>

thermal mitigation pilot. An example of an<br>

alternative option for thermal mitigation.<br>

To read more click here: [https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/thermal-mitigation/evaluation-shade-balls-mitigating-summer-heating-stormwater-management-ponds Shade Balls study]<ref>Rocha, L., and VanSeters, T.2020. Evaluation of shade balls for mitigating summer heating of stormwater management ponds. Toronto and Region Conservation Authority, Vaughan, Ontario. https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/thermal-mitigation/evaluation-shade-balls-mitigating-summer-heating-stormwater-management-ponds/</ref><br>

</br>

===In the Stream Corridor===

===In the Stream Corridor===

Riparian plantings are the primary means of preserving or reducing thermal enrichment of streams.   

Riparian plantings are the primary means of preserving or reducing thermal enrichment of streams.   

These strategies work best for small streams with high vegetation or trees that provide significant reductions in light intensity.  Studies have shown that streams with extensive riparian shading have maximum summer temperatures between 1 or 2 degrees lower than unshaded streams (AECOM, 2009<ref>AECOM Canada Ltd. 2009. Hanlon Creek Business Park stream temperature impact report, continuous modelling with HSP-F. A report to the City of Guelph. https://guelph.ca/wp-content/uploads/HCBP_EIR_Report.pdf</ref>; Dugdale et al., 2018<ref>Dugdale, S.J., Malcolm, I.A., Kantola, K. and Hannah, D.M. 2018. Stream temperature under contrasting riparian forest cover: Understanding thermal dynamics and heat exchange processes. Science of the Total Environment, 610, pp.1375-1389. https://www.sciencedirect.com/science/article/pii/S0048969717321952</ref>).<br>

These strategies work best for small streams with high vegetation or trees that provide significant reductions in light intensity.  Studies have shown that streams with extensive riparian shading have maximum summer temperatures between 1 or 2 degrees lower than unshaded streams (AECOM, 2009<ref>AECOM Canada Ltd. 2009. Hanlon Creek Business Park stream temperature impact report, continuous modelling with HSP-F. A report to the City of Guelph. https://guelph.ca/wp-content/uploads/HCBP_EIR_Report.pdf</ref>; Dugdale et al., 2018<ref>Dugdale, S.J., Malcolm, I.A., Kantola, K. and Hannah, D.M. 2018. Stream temperature under contrasting riparian forest cover: Understanding thermal dynamics and heat exchange processes. Science of the Total Environment, 610, pp.1375-1389. https://www.sciencedirect.com/science/article/pii/S0048969717321952</ref>).<br>

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</br>

 

[[File:Riparian veg stream.jpg|500px]]<br>

File:Riparian veg stream.jpg| A stream with mature Riparian vegetation surrounding it to help reduce thermal enrichment. Photo Source: [[Acknowledgements|TRCA]]

A stream with mature Riparian vegetation surrounding<br>

it to help reduce thermal enrichment. Photo Source: [[Acknowledgements|TRCA]]

==References==

==References==