Cold water fisheries require high oxygen content, which in turn requires relatively low water temperatures. Where significant groundwater movement occurs, the groundwater can have a temperature entering the stream of the annual average air temperature. But that requires long contact time and large surface areas. We can get down to cool-water temperatures using bottom draw ponds that are sufficiently deep - in the order of 3m, with an outlet at something like 1.8m deep. But regardless of what we do in the SWM pond, we're limited by the dewpoint, which in the summer in Ontario tends to be above cold water temperatures. How do we get there?
Dear Douglas,
Here are some links that may answer your question
http://www.naturalchannels.ca/files/presentations/T2A_3_David_Arseneau.pdf
https://www.chijournal.org/Content/Files/R246-12.pdf
http://your.kingcounty.gov/dnrp/library/wastewater/wtd/construction/Brightwater/FEIS/V04-10/06-J.pdf
With my best regards
Prof. Bachir ACHOUR
The best stream we had in temperature surveys within the Chattooga River watershed in the Blue Ridge Mountains was Bad Creek -- it was mostly wilderness area with good forest cover over most of the drainage area (attachment). The interesting thing was it had the highest winter temperatures in comparison to the other streams we looked and the lowest summer temperatures. I think the summer highs were about 18 degrees C in Bad Creek, and air temps might reach 35 degrees C and back down to 25 degrees or less at night. In the winter, snow that gets to the ground does not melt as fast under a tree cover as opposed to open. So I would try to get fast growing, but tall cover over your stormwater ponds for shading and insulation. If you can make them deeper than 3 m, that may help. There will be difference in a surface pond with dam that results in a pond 3 m deep and a hole dug into the ground that averages 3 m deep. If in Ontario, my guess is the ponds are too shallow or they are not getting as much groundwater as you think. I have also found that if there are cold water inputs such as side tributaries, fish will congregate to these inputs from cooler areas during high temp stress and apparently relocate temporarily to these cool spots or deeper waters to survive higher temps, but they don't eat, they just weather the heat.
Thank you;
Both of these responses are quite helpful, but illustrate the problem I am trying to resolve.
Ponds more than 3m deep run into problems with maintenance by the municipalities. Fast growing cover over the whole pond would be like a vegetated floating island? That has been tried, and it shows up as a fantastic goose habitat, slightly decreasing water temperature (about 1C water temperature drop), but vastly increasing BOD, DOC, e.coli, NO3, NO2, NH3, etc... Tree cover doesn't help much, since 20 years from now the shadow will be 10m wide, while the pond is 100m wide.
We try to design to prevent groundwater interference for several reasons.
- If the ponds are constantly flushed, the sediment doesn't settle and ends up being washed into the stream
- If the groundwater would have reached the stream during the summer, then the heat from the pond is reaching the stream anyway, and there is no change in the impact on the fish
- In periods of high groundwater, there is less volume available to mitigate downstream impacts from storm events.
I would like a method that can be used to predict the peak temperature being released from a pond, and be able to demonstrate that changes in the design will correspond with specific release temperature changes. Seems to be the only way to do this is by using some form of geoexchange, but I haven't seen any literature on this being used effectively to address the release temperature of a storm pond.
- Badges
- Science topic