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Watermelon snow and its effect on Utah’s water supply

If you’ve ever spent any time out in the snow, you know just how often you need to reapply sunscreen to avoid getting sunburned. That’s because snow is the most reflective naturally occurring surface on the planet. That reflective nature plays a huge role in Utah’s water supply, but brightly colored algae, dust from the Great Salt Lake, and air pollution can all settle on the snow. This not only changes the color of the snow but also affects Utah’s water supply.


Utah is known for being home to the greatest snow on earth. It’s dry, fluffy, and extremely reflective. However, mountain snow may not be as great as it once was.


“A lot of people call it watermelon snow,” Scott Hotaling told ABC4. Hotaling is an assistant professor at Utah State University’s department of watershed sciences. He explained that in spring, patches of pure white snow can turn pink or even deep red. “And that’s actually a green algal bloom that’s occurring on the snow’s surface.”


Algae needs water to survive and is often associated with warm water. Algal blooms are common at lakes across the state near the end of the summer when conditions become perfect for this to occur.


So, how does snow algae survive in such frigid temperatures?

“The snow algae produce a pigment that basically darkens their cells, and it acts as both a protection against UV,” Hotaling explained. “So, it protects their DNA and other aspects of their organelles from damage because they’re in such a bright place. But then also, it has a secondary benefit of causing their cells to absorb heat which melts the snow around them which allows them to actually access water because, you know, we’re out here in a world of water right now but none of it is accessible.”


Since snow is so bright, it usually reflects the sun’s energy back into space. This keeps the snow cooler for longer. This is great for runoff. Mountain snowpack can last well into the summer months thanks to this natural insulation. However, watermelon snow melts much more quicker.


“A group from the University of Alaska looked at what the contribution was of snow algae to total melt of an ice sheet over the course of a summer and it accounted for about 15 percent of all of the meltwater that came off that ice field was because of these algal cells,” Hotaling stated.


He is working to figure out how much of Utah’s snow melt is a result of algae. The research is in its infancy but could see results within two years.


So, why should we care?


Hotaling answered the question by saying: “Snowpack decline around the West impacts how much water flows out of the headwaters which is then how much is available for agriculture, and people and then what actually makes it to the Great Salt Lake.”


Hotaling emphasized that the algae itself aren’t an enemy. In fact, it’s most likely been here much longer than people. However, he explained that it may be becoming more prevalent. Humans may be partially responsible.


“It’s entirely possible that the dust and other factors coming off of the Great Salt Lake, inversions, all these kinds of things, and other particulates actually have nutrients attached to them, nitrogens and things like that can, in turn, promote algal blooms,” he added.


The Great Salt Lake. Roughly half of its lakebed is exposed thanks to low water levels. While the lake’s water levels drop by two feet (on average) every year due to evaporation, it usually regains that water from snowpack runoff. However, overconsumption of water has caused the lake to continually shrink. The exposed lakebed is particularly troublesome during the windy spring months for a few reasons.


The dust is known to have metals and other toxins that could be detrimental to human health. Not only that, but it could also be feeding the snow-melting algae. Even in areas where there aren’t algae growing on the snow, the dust itself may add to early melting.


“And it’s not just Great Salt Lake, we have dust sources further afield,” Dr. Daniel Bedford told ABC4 News. Bedford is a professor at Weber State University’s department of geography and environment sustainability. He’s been studying the Great Salt Lake and its decline for years.


Bedford explained: “Certainly, those dust sources deliver dust onto the snowpack and once the snowpack loads these things up, it darkens the snow, it melts the snow faster, so it’s influencing, again, our water supply, so it’s this feedback loop of us affecting the lake and the lake affecting us in terms of water.”


“We really need to understand how that human influence might circle back to an ecological influence that happens in our headwaters and literally what happens up here is what matters for down there,” Hotaling said while pointing down the mountain towards Cache Valley. “We all live downstream in Utah.”



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