Maddie Harasyn sampled 21 different locations in the two main lakes during the spring and summer. We located these sites from the detailed bathymetric mapping that Alexandre Normandeau completed in 2015. This allowed us to find the best locations to test for the presence of groundwater seeping in over the winter.
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| 2015 Bathymetry from sidescan sonar (from Normandeau et al. 2016). Purple and blue colours represent the deepest areas of the lakes. |
Measuring the water at the bottom of the lake is a real challenge. We use instruments that are lowered on a rope down through the lake from the ice cover. Imagine putting something the value of a car on the end of a $5 rope and you get the idea! We slowly lower the instrument as it collects data at 3-second intervals. That part is very standard.
The problem is that we want to avoid touching the bottom sediment because this will disturb the last measurements and contaminant the water samples with sediment. In 2016, we avoided this by using a live video feed on the instrument. So as one person lowered the instrument, another carefully watched the screen. To know when we were near the bottom, a flashlight was directed downwards. As it approached the bottom, the beam of light came into focus and then became very small, alerting us to stop in time.
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| The CTD-video-light-water sampler unit. All designed to go through a hole in the ice. |
We are working on the results now, but this effort appears to have been worth the trouble. It is all part of the challenges of working in the Arctic and doing research.
