snow survey process

Monitoring water levels is a year-round endeavour for Cataraqui Conservation staff. It’s an important component in fulfilling a key part of the organization’s mandate to help predict possible flooding.

For the warmer seasons of the year monitoring water levels in the Cataraqui Region is relatively easy to come by, as measuring tools can be dipped into streams, lakes, and rivers or rain falls into special rain gauges at designated locations. In the winter, it’s a bit more complicated, mostly because a sizable portion of that water is now on land in the form of snow and ice. But it still needs to be measured in order to discover whether there may be an overabundance of water when it melts.

One of the many duties of Cataraqui Conservation’s Co-ordinator of Watershed Planning Holly Evans is to measure the depth of snow at various locales throughout the Cataraqui Region and calculate approximately how much water will be heading into the area streams and lakes once the warmer weather arrives. This is known as the Snow Water Equivalent (SWE) – the amount of rain measured in millimetres that would be contained in that snow melt.

Evans explains her method:

“There are seven snow survey stations located throughout the Cataraqui Region and at each location I take 10 core samples from the snow. The sample points are evenly spaced along a 270 metre long transect, which is usually on a straight line if there is enough space on the property. A bucket and a snow corer [which is a long hollow tube with teeth at the bottom] are used to take snow samples. At the first point, the corer is pushed through the total depth of snow, the snow depth is noted, and the corer is gently removed from the hole,” she said.

“The snow sample is put into the bucket that is lined with a plastic shopping bag and I move on and collect and measure the remaining points at that site. I have an app on my phone where I record the snow depth for each location and any special notes I want to remember. After the 10 samples are collected, all the snow is weighed by hanging the plastic bag from its handles by a hook on a digital scale. This tells me how many grams of snow have been collected from the ten cores. And because I know the depth of the snow in the tubes and how big around the tube is, I am able to calculate the volume of collected snow. Knowing how much water weighs, it’s then possible to determine how much water or snow water equivalent is at that particular location based on the average snow depth.”

snow survey process

As well as measuring the depth of the snow, Evans also records whether the ground is frozen and if there is an icy crust on top of the snow and how thick it is and gives a general impression of it’s thickness by saying whether there is no crust, a thin glaze, or perhaps its thick enough to support a person with snowshoes or even a person without snowshoes. This crust of ice on the top can be quite impenetrable, meaning any rain or snow melt on top will run right off. If there is enough of this runoff, it could lead to flooding downstream.

Snow survey stations are located just north of Sydenham, on the northern edge of the Little Cataraqui Creek Conservation Area in Kingston, another near Battersea, one close to the airport in Gananoque and the remaining three in Delta, Athens and Brockville. Evans explained that there are none in the westernmost portions of the Cataraqui watershed because of the close proximity of survey stations operated by neighbouring Quinte Conservation. From Nov. 15 through May 15 (as long as there is snow) Evans performs these 70 samples every two weeks.

“Conservation authorities and others such as Parks Canada in the province do snow surveys. We look at ours locally, but we also submit the results to the provincial Surface Water Monitoring Centre, which is run by the Ministry of Northern Development Mines Natural Resources and Forestry. They report on snow surveys throughout the province and twice a month we get a report from the ministry showing the snow depths and snow water equivalents throughout Ontario,” said Evans, who added that the importance of collecting this information month after month, year after year is to help the flood forecasters determine whether warnings and mitigation measures need to be put in place during the snow melt.

“Without this information it would be guesswork as to how much snow is on the ground and thus how much water was on the landscape, so you might be making mistakes in your forecasting. And it’s especially important these days because in years gone by, the one and only time we needed to worry about flooding was during the spring melt, but that’s not the case anymore. These days there are several times when melts are happening even in the dead of winter, so this information is important throughout the winter now.”

Due to the more frequent incidences of melting and rain, as well as extreme temperature fluctuations, layers of ice intermingle with layers of snow like a frigid layer cake. Evans has to make note of these harder layers as well and has had to become innovative and adaptive in order to be able to still make accurate measurements even through tough ice.

So, in the midst of fancy apps and mathematical equations, she ‘MacGyvered’ a special tool to help speed up the process. Seeing that the measuring tube, even with some pointy teeth at the bottom, was not strong enough to break through some ice layers, she took two hole saws (like you use to make holes in doors for door hardware) and had a local welder weld one on top of the other. Using a drill, she then is able to more easily collect the harder icy layers and enable an accurate sample.

snow survey equipment

“Without the hole saw tool, I could try to use an ax to chip up the icy material and try to ensure the proper diameter sample is collected, but I thought my snow drill would be better. Actually, often I have to make my own tools for my monitoring work. There is always a situation in the field that doesn’t fit the tools you already have.”

For the 2022 spring melt, Evans’ snow survey results show that there is an abnormal amount of snow still on the landscape (as of March 11), meaning a heightened possibility of flooding.

“We have the historical data [from as far back as 1971 for some stations] in our data management system so that long-term normals can be determined snow depth and snow water equivalent per site and we can say how far off the current results are from normal. At the beginning of March there was 11.5 centimetres more now on the landscape and 37.3 millimetres more water on the landscape than usual. That’s the equivalent of a pretty big rainstorm.”

For more information about Cataraqui Conservation's role in flood forecasting and warning, visit