A critical component to the work Cataraqui Conservation does in forecasting and warning about possible flooding throughout the region is understanding the amount of water on the landscape during all four seasons – including during the winter.
Twice a month, from the end of November through to mid-May, as a way of getting a sense of how much run off will occur during the annual spring melt, staff regularly measure the amount of snow on the land. This is called a ‘Snow Course’ or “Snow Survey’ and involves heading out to a number of pre-determined locations throughout a given territory and measuring the snow depth and weight. The sites of the courses never change and neither does the way in which the snow is gathered at each location, according to Cataraqui Conservation’s Coordinator of Watershed Planning Holly Evans.
“The way that we know how much water is sitting on the landscape is by visiting representative sites across the watershed and utilizing a standardized data collection method used all across the province for the Surface Water Monitoring Centre, which is a branch of the Ministry of Natural Resources and Forestry,” she said.
“We use a snow tube, or corer, and we push that down into the snow pack and measure the depth on the side of the tube and then take the snow that we collect from the tube and put it into a bag. We do that 10 times at each site and it’s a standardized distance between sample points; for me that’s 18 paces. So, I am out there counting to 18 many times: seven sites and 10 samples per site, so that’s 70 times in a day. And while it only takes me maybe 15 minutes per site, there’s all the driving in between that makes it pretty much a full day.”
After collecting the 10 bags at each site, it’s weighed, which lets Evans know how much water is in the snow, because the weight of water never changes. And she also knows the volume, because she already knows the volume of the space in the tube.
“That tells me how many millimetres of water is sitting on the landscape in that general area so when we have a melt event, we know how much to expect running off the land and into waterways, which is why it’s primarily used for flood forecasting and warning,” Evans said, adding that this information is then forwarded to all the water managers in the region to help in their overall forecasting plans.
“I tell our area water managers in a direct email and I also copy the Surface Water Monitoring Centre giving them a summary report, which includes the average snow depth or the average Snow Water Equivalent (SWE). At this time of year I will also tell the water managers how the results compare to the normal, and the normal is the average on that collection date back over 30 years. You could use the data for understanding the impact of climate change as well. For us, on a day-to-day basis it’s really more about how much water is sitting there right now.”
Besides looking at the depth and measuring the amount of snow in each sample, Evans also makes note of whether there is any icy crust on top of the accumulated snow, as well any stratifications of ice within the sample.
“There are a few different classifications of crust: no snow, no crust, a slight surface glazing, a light crust that doesn’t hold the weight of a person and a strong crust that can hold a person. This tells you how resistant it might be to melting and also if you get rain on top of a really hard crust it can act a bit like pavement and just run off faster,” she explained.
“I do make some notes about the stratifications of crusts. There really isn’t an opportunity to be that detailed at each site, at least not in the collection method that they give to us. But I will make some notes if there is a particularly crusty section partway down, or if there is a layer of ice – sometimes there is a layer of ice that develops between the ground surface and the first bit snow. So I add that to my notes. I also record soil conditions s about whether the ground is: frozen, unfrozen and wet ground or unfrozen and dry. Obviously right now (February) it’s pretty easy to determine that it’s frozen.
For more information on Cataraqui Conservation’s various watershed monitoring programs, visit https://cataraquiconservation.ca.