Lidar (Light Detection and Ranging) has been successfully used to map the depth of snow cover on the eastern slopes of the Alberta Rocky Mountains. The existence of this data allows us to accurately evaluate the amount of water available in the snow cover. This data is vital to determining how much water will leak downhill after the snowpack melts.
The measurements were taken by teledina Geospatial. Using a Teledyne Optech Galaxy T2000 lidar Using the system mounted on a Piper Navajo aircraft, surveyors were able to map 250 km² of mountain slope in just one hour. The hundreds of millions of individual aerial LIDAR measurements were compiled into a high-fidelity 3D model of the mountain slopes. In contrast, the manual method of walking and sticking a measuring stick into the snowpack would have only captured a handful of points and would not have covered more than 3 km² in the same time period. The research project was led by University of Lethbridge principal investigator Dr. Chris Hopkinson and sponsored by the Government of Alberta.
“Our technology is capable of obtaining a 3D map or model of what the terrain looks like,” explained Malek Singer, aerial product manager at Teledyne Geospatial. “To do this, we first flew over the bare mountains, without snow, before the winter season. That gives us a good baseline, a very high resolution model of what the terrain looks like. Then we fly again in the peak of snow, say something around April or March, before the snow melts. And the difference between these two models, that is, the bottom of the soil and the top of the snow cover.”
Using this data, Dr. Hopkinson's team determined that the average snow depth on the eastern slopes “was around eight feet for the most part, in mountain slope watersheds.” Singer told SpaceQ. “In terms of snow/water equivalent, I think the average was about 20 centimeters; That is, there are 20 centimeters of water in that mountainous terrain.”
As for the importance of lidar measurements? Beyond providing an accurate picture of water resources in this part of Alberta this year, the data is a wake-up call for government officials. “I think those numbers are somewhat alarming for decision makers and people who monitor these resources because they are probably below the historical snow/water equivalent average,” Singer said.
That said, it was not Teledyne Geospatial's job to solve Alberta's water problem, but simply to provide accurate data about it to the study team. On this point, Dr. Hopkinson was impressed.
“Aerial lidar has proven to be a viable method for mapping snowpack depth, sampling, and imputing units in forested and mountainous environments,” he said in a news release. “LIDAR data, when processed with terrain information, land cover data and satellite imagery, allows for continuous imputations of snow depth. “This is crucial for calculating snow water equivalent (SWE) at the sub-basin scale, which informs water availability and directs management strategies, particularly in the emerging drought situation in Alberta this year.”
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