During our first major snowfall of the season, FortWhyte Alive staff Katrina Froese and Danielle Mondor headed out onto the ice to take measurements that tell us about the health of FortWhyte’s lakes. As part of FortWhyte’s efforts to get a better handle on what’s going on in our five clay pit lakes, monthly water monitoring has been underway since April 2013. While water testing during the summer months is done by canoe, in winter, we get to head out on foot into a snowy wonderland, towing a sled with our testing equipment.
Safety is always first. Our first step is to drill our battery-powered ice auger through the ice to determine thickness. The first test showed us the ice thickness was seven inches off the Lake 3 dock – good to go. Two of our lakes, Lake Devonian by the main road and Lake Cargill to the north, are aerated. Out in the middle of the lake is an open patch of churning water. While these lakes are typically safe so long as one stays clear of the aerator hole, these lakes were off the list for this round of water testing, given a warm winter and inconsistent freezing on those lakes.
At each sample site (the deepest point in each lake) we drill a hole, and lower a YSI probe at 1-metre increments to measure temperature and dissolved oxygen levels. Our deepest lake, Muir Lake, is 7.9 m deep, while our shallowest, Lake 3, measures 6.1 m.
So, what do oxygen levels tell us? For one, we’ve found that our aerated lakes sustain enough oxygen during winter to support fish populations, but with solid ice cover, our non-aerated lakes experience an oxygen crash. By mid-January, at well below 10% saturation, any fish that hadn’t moved to Devonian in fall would not survive due to lack of oxygen.
Our last task is to take a water sample that is later sent to a local lab to test total phosphorus levels. Phosphorus is a plant fertilizer that is limiting in freshwater -- basically, the amount of phosphorus has control over the growth of algae. Our lakes have been found to have high levels of phosphorus -- which is pretty easy to observe in summer when we see large algae blooms forming. Sources of phosphorus include soil erosion, waterfowl feces and the sediments of the lakes themselves, which accumulate over time. Interestingly, we are finding that phosphorus levels in the lakes rise in the winter: a lack of oxygen results in the release of phosphorus from the sediments.
As we continue into 2016, we will be looking to add a new measurements to our monitoring to help us better understand the timing of phosphorus release from sediments, and we are continuing to be open to new solutions to reduce phosphorus concentrations.
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