Update: Here’s a CBC article on this topic – click here.
Water Quality Testing Maps the Health of a Lake
During these short winter days, while the lake sleeps under its blanket of ice and snow, there is still plenty of activity going on around Williams Lake. People have been skating, cross country skiing, snow-shoeing, and noting the animal tracks, deer, and bald eagles that visit this time of year for crucial winter hunting. And here at the Williams Lake Conservation Company (WLCC for short) this is no less true. Winter is a time when much valuable work is done.
Last Fall, just before the lake got it’s frosty covering, we were out on the water, taking samples as part of our yearly water quality assessments. At various times of the year we test things like temperature, acidity, and oxygen levels, but measuring salinity, or levels of salt, is one of the most important things we do. The wildlife that abounds in the watershed area – the deer, mink, osprey, beaver, hawks, herons, turtles and other animals that are regularly sighted – are all a function of the life-giving and life-sustaining lakes at the centre of the Backlands. And the health of the lakes is directly related to the amount of salt that finds its way into the water.
There are many lakes in HRM like Chocolate Lake that, while pretty to look at and safe to swim in, are dead zones biologically. They cannot support the fish, frogs and insects that form the foundation of a vibrant food chain. But the Backlands is still home to a wide range of living things. That’s at least part of the reason this area was chosen by the Nature Conservancy of Canada as a significant natural area worth protecting and preserving. Monitoring and minimizing salt levels in the lakes is a key step in keeping the area healthy and full of biodiversity. Here’s why.
Without getting too technical, salt or “sodium chloride” interferes with a process that happens in healthy natural lakes called water turn-over. Burkhard Plache, a member of the WLCC and the person responsible for drawing samples, explained how it works. We joined him on the shore one brisk November day last year to help load his wooden canoe with water testing equipment, generously on loan from the Community Based Environmental Monitoring Program associated with St. Mary’s University. With him were two assistants Caroline Stratford and Younhaee Yu, students in the Environmental Engineering Technology program at the waterfront Dartmouth campus of Nova Scotia Community College, to help measure oxygen, pH value, temperature and salinity.
Basically oxygen levels are a measure of the health of the lake. Low oxygen signals that the lake won’t support as much life (think “fish” and all the things that eat them, then all the things that eat the fish-eaters). Typically the top layer of water has lots of oxygen, with almost 100% saturation – while the deepest parts of the lake have lower oxygen. But this situation is fixed in late Fall by “lake turn-over” where the cold surface layer sinks and mixes with the lower part. So far so good, but this is where salt plays its deadly role.
Both Williams and Colpitt Lakes are fed by huge watershed areas, with water that drains off the hard rocky ground. If roads, sidewalks and driveways in the area are salted, this salt is washed into the lakes. Salt accumulates at the bottom of the lake where it makes the water more dense and prevents turn-over. Without mixing, the bottom layer does not have enough oxygen to support life, and the deepest parts of the lake slowly die. Bacteria are unable to consume waste matter, and the lake becomes progressively more polluted with undigested organic matter. Not a pretty sight. All wildlife that depends on fish are impacted – eagles, mink, osprey, heron and more.
The good news is that presently, the Williams Lake water appears to be mixing just fine. On that November day, the water temperature was a steady 5.3 degrees from surface to lake bottom – in some places as deep as 23 metres! However, there is no doubt that salt levels increased after road salting in the area was resumed in January 2015 after decades of sanding only. A Report on Water Quality on our Issues page (see link here) by David Patriquin in December 2015 showed an uptick in salt loading and delayed water turn-over – both very alarming. We must not forget the chilling examples of Chocolate and Oathill Lakes, where salt and other run-off contaminants like pesticides, herbicides and pet waste have damaged the water’s health, and with it the surrounding web of animal life. While salt levels in Williams Lake may continue to creep up, it is not too late to intervene.
Members of the WLCC are committed to monitoring the health of Williams Lake, resting as it does at the apex of a natural area that abounds in wildlife, and to working with the City to minimize or end the salting of area roads and sidewalks (for an update on the road salting issue see the blog post Breakthrough on Road Salting ). The importance of not salting is a community issue as well. Residents within the watershed of both Williams and Colpitt Lakes are urged to use sand or grit instead of salt, or to seek out safer alternatives for walks and driveways. Local hardware stores offer de-icers that use calcium chloride, and some that dispense with “chlorides” altogether. While salinity is within safe limits right now, it is expected to rise further in future, so every attempt to remove it from the environment should be taken now. We can all do our part.
HRM has recently recognized the significance of having healthy lakes within its borders, and is considering using Williams Lake as a “base line” in a pilot study to compare lakes in the city. With our decades of water quality measurements, the WLCC is well-placed to show how housing and road maintenance policy have a direct impact on the health of lakes. We can also help point the way to safe practices that will preserve HRM’s “blue necklace” of unspoiled lakes for generations to come. We should strive for nothing less.
If you’ve made efforts to limit the use of salt or other contaminants, we’d love to hear about it. Just go to the Contact Us tab at the top of this page, or click here.