The ice has melted away and the signs of winter are gone for another year, Lake Windermere is undergoing a variety of changes, beyond the obvious change in state. This thaw provides more than just excitement of boating, swimming and paddling opportunities that await in the coming months, it wakes the lake up with spring turn over. While Lake Windermere is unique in that it doesn’t see typical stratification – separation within the water column based on water temperature – we do still see the leap of life at this time of year.
The average freshwater lake will stratify into three distinct layers – epilimnion, metalimnion, and hypolimnion. These layers are defined by their depth, temperature and dissolved oxygen, with the epilimnion (at the top) being the warmest with high levels of dissolved oxygen, and the hypolimnion (at the bottom) being the coldest with lowest levels of dissolved oxygen. The reason for this stratification has to do with the density of water at different temperatures. You may have experienced this phenomenon while swimming and finding the water at the bottom of the lake is cooler than that at the surface.
When the ice melts in the spring we see a mixing of these layers that is essential for aquatic organisms. When the ice cover melts, and the lake is exposed to the fresh air again, the wind and warmer temperatures initiate the mixing process. The surface water will begin to warm until it reaches 4°C – temperature at which water is most dense – and will then sink, continuing the turnover process. This is critical to aquatic organisms as the surface water brings with it dissolved oxygen – essential for life in all parts of the water column – that has been depleted over the winter months.
Since Lake Windermere is shallow, and if you have been here a while you will know it gets rather windy, this process all happens quite quickly! You may have heard of our summer monitoring program that runs weekly from May to September, but to have a greater understanding of the current condition of the lake the Ambassadors strive to capture information about the water column in all of these stages. This year we were able to collect a small amount of data in late February from under the ice, and a larger in-depth sample within two weeks of the ice melting. This information gets added to the historical data for Lake Windermere that we review annually to understand the state of the lake and rising concerns the be aware of.
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The Lake Windermere Ambassadors would like to thank the Columbia Basin Trust, Columbia Valley Community Foundation, Columbia Valley Local Conservation Fund, Real Estate Foundation, BC Gaming Grants, District of Invermere, Regional District of East Kootenay and community donors for supporting our 2021 programming.