Changes

===Shade balls===

===Shade balls===

<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>

Since direct solar radiative heating of water is the primary cause of pond thermal enrichment, partially covering the ponds with a material that reflects solar radiation should, in theory significantly reduce the warming effect, resulting in cooler outflows.  

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.

As a result, hollow, white, high density polyethylene balls were installed in  Esker pond in Brampton in the summer of 2018. The shade balls are roughly 10 cm in diameter and their white color was selected for their assumed higher albedo and capacity to reflect sunlight compared to black balls that were also available from the manufacturer (Bird-X). Typically referred to as bird balls the product’s main applications are to prevent waterfowl from landing on toxic tailings and airport ponds, and to block UV light from drinking water reservoirs to prevent the formation of carcinogens (e.g. bromine and chlorine reacting to form bromate). They are also used to prevent evaporation from pond surfaces, which can be useful for keeping water in a reservoir but also for preventing odours leaving facilities like waste water treatment lagoons. According to the supplier, the balls do not upset oxygen circulation or harm fish or other wildlife using the water body.<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>

 

The floating white balls can be placed in a stormwater pond to cover its surface with a high albedo material that reflects incident solar radiation, deters bacterial contamination from birds, and allows heat transfer from the pond to the air during days and nights when air temperatures are cooler than the pond.<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>

 

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

==References==

==References==