Snow and rain: A tortoise and hare story

March 20th, 2015 | Kate Burchenal

Here in Colorado, we tend to think of precipitation in discrete, measured amounts: Inches of snow, cubic feet per second, acre feet of water. In an arid region often afflicted by drought, this is an understandable way to perceive our water situation. But if we dig deeper, the issues we face surrounding water are much more nuanced than simple measurements. Two other factors related to precipitation, the timing and type, are just as important as the amount, if not more so.

As any boater or skier will tell you, a storm bearing an inch of rain in July is very different from a system dropping an inch of rain in January. Though they may produce the same amount of precipitation, all storms are not created equally. Rain and snow are both welcome forms of precipitation and serve their own purposes, but the effects and consequences of each are quite different.

It is a classic case of “the tortoise and the hare.” Rain, the hare, moves quickly through watersheds, rapidly passing from cloud to ground to waterway and beyond. On the other hand, snow (the tortoise) stockpiles water in winter, gradually releasing it into waterways through spring runoff. Rain has more immediate benefits to and effects on the system, while the impacts of snow are on a time delay. I think we all remember who wins the metaphorical race.

For our rivers and streams and for our recreation-based economy, it is imperative that the majority of our annual precipitation (approximately 80 percent) comes in the form of snow. For a few important reasons, rain just won’t cut it.

Importance of Snowpack

Generally the highest flows of the year are fueled by the spring snowmelt, not rainfall. The intensity and volume of water during peak runoff scours river beds, making them more suitable habitats for fish and bug populations. Through the dry summer months, runoff from the remaining high-altitude snowfields bolster low flows and help maintain cool water temperatures for sensitive trout species. And finally, decreased snowfall negatively affects groundwater recharge. As previously mentioned, rain water (the hare) moves quickly through a watershed, increasing the likelihood of flooding and decreasing the ability of the ground to absorb precipitation into the water table.

Snow Water Equivalent

Skiers are constantly tuned into the snowpack for many reasons: To understand snow stability and avalanche danger as well as to know how this season stacks up to seasons past. In the water world, we are acutely aware of the snowpack as well. However, we aren’t looking at the base reports from ski areas or the season snowfall totals. Instead, we look at a measurement called the snow water equivalent. While snow water equivalent is also measured in inches and is inextricably connected to the measurements previously mentioned, it is used to understand how much water is stored on our slopes at any given time.

This year, throughout Colorado, we have been hovering at or a bit below the average snow water equivalent. As I write this article, the basins range from 73 percent to 101 percent of average (the San Juan and South Platte basins, respectively) with the Upper Colorado Basin at 91 percent. While we would certainly rather be above average, we are in a much better position than our friends a few states to the west.

A quick perusal of California’s Sierra Nevada shows snow water equivalents ranging from 0.1 percent to 25.8 percent. Yes, you interpreted that correctly. The snowiest place in California is currently sitting on just over a quarter of its average snow water equivalent. These numbers are clearly devastating for California’s ski industry, but the negative consequences are and will be much more far-reaching than that.

We all may be sick of shoveling and slick roads by the end of winter, but we can’t forget how vital snow is to our economy, our environment and our mountain way of life. So let’s all root for the tortoise and pray for snow!

Kate Burchenal is the Education & Outreach Coordinator for the Eagle River Watershed Council. The Watershed Council has a mission to advocate for the health and conservation of the Upper Colorado and Eagle River basins through research, education and projects. Contact the Watershed Council at 970-827-5406 or visit www.erwc.org.

This article ran in the Vail Daily on March 20, 2015.