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Flagstaff region snowfall about average; what that means for forest health and water supply

A snowy forest with pine trees
Melissa Sevigny
Snow in the ponderosa pines south of Flagstaff

The Flagstaff area has received almost one hundred inches of snow so far this winter. That’s about average for the region, but it follows a stretch of dry winters that have drastically shrunk local rivers and reservoirs. KNAU’s Melissa Sevigny spoke with Salli Dymond, a forest hydrologist at Northern Arizona University, about what this winter’s snowpack means for the future.

How is this going to help us with the regional water supply?

One thing that’s really great about snow, if you think about it—it sits on the landscape for a little bit longer, and so it infiltrates into the soil over a longer period of time… The snow here is really important for recharging what we call deep soil water, and that’s what the trees tap into during the dry season, thinking into June or July. So having a good snow year is incredibly important for thinking about healthy forests particularly during fire season.

How does having the soil being filled up with water—how does that help with our local rivers and reservoirs, is that connected at all?

It’s very connected. We think of the soil as a big sponge, right? The first thing is the snowpack is going to do is it’s going fill the soil reservoir. It will infiltrate and move down into that soil sponge, and then once that soil sponge is filled up the rest of that snow water is going to move over the surface of the soil and down into our local reservoirs, like Lake Mary, and down into the streams. You might see them streams flowing right now. It’s a great time to look at waterfalls and see the streams flowing.

A little further afield, is this year’s snowfall going to make a dent on the big reservoirs on the Colorado River that are so low right now?

The Colorado River is so low because we’ve had so many years of very severe drought, so while it certainly helps, it’s going to take many years or normal to above normal precipitation in the winter and the summer to really see a dent in the Colorado River.

That makes sense, and the bad news with climate change is things that normally would fall as snow are falling as rain, why is that a problem?

The problem with the rain is that when you look at the precipitation for the whole year, yes, we’re getting above normal precipitation, but what we don’t get is that water falling and infiltrating into the soil… The water comes too fast, too intensely. The snow is great, because even when it comes during a heavy event, it can stay on the landscape longer, because it comes when it’s frozen, so the snowmelt happens at a more gradual pace.

Let’s talk more about the upcoming fire season. I know people are always interested to try to forecast, is it going to be a bad a year or a better year because of the snow on the ground?

The snow certainly helps. If we have a nice moist soil that helps for the tree staying less dry. Essentially one of the things we’re concerned about is the downed fuel: is that fuel dry or does it have some moisture to it. Again with the live fuel as well: Are the crowns of the trees really dry or do they have some moisture to them?.... It’s all connected, that’s one of the interesting things. The water, the forest, it’s all intertwined. Think about that! I know everybody’s a little tired of the snow, but healthy snowpack means a healthy forest, so think about that as your shoveling. It will certainly help us as we get into our fire season.

Salli Dymond, thank you so much for speaking with me.

Thank you for having me.

Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.