Inspired by the 70-degree temperatures that have settled in recently, last week I invited a couple of writer friends over for lunch al fresco. While we sat in my yard under a cloudless sky, eating cauliflower-and-leek omelets and gabbing about work, the butter pooled in its glass dish and a bar of chocolate melted in its wrapper. All of which was a bit disconcerting, given that it was early March. In Boulder, Colorado.
My season ski pass, meanwhile, sits forlornly in my desk drawer. Some nearby ski resorts are sill less than 100% open, and at Vail the current base is a measly 43 inches. The mountain snow reports are the same, day after day. New snow: Last 24 hours, 0″. Last 48 hours, 0″. Last 7 days, 0″.
Colorado gets its water from the mountains. It falls as snow and eventually melts into streams and rivers, which deliver it to reservoirs and city taps. Without snow, there is no water except what we’ve stored in those reservoirs in previous years of plenty. And reservoir water, while great for humans, does nothing to help nature cope with drought.
So while I confess I kind of liked reading The New Yorker in my yard in flip-flops and a t-shirt this weekend, admiring my about-to-bloom tulips, it also scared the crap out of me. What will this place look like come summer? Will whole neighborhoods go up in flames at the first lightning strike? What will the wildlife do? Will there be any water in the ditches where my dogs like to swim? Will I be allowed to water my yard?
I contacted Mark Williams, a professor of geography and a fellow at the Institute of Arctic and Alpine Research here at the University of Colorado. Williams is an expert in snow hydrology, and in how water moves through mountain watersheds. (He also studies biogeochemical cycling and acid mine remediation.) I figured if anyone could explain how worried we should (or shouldn’t) be, it’d be him. The good news is, I probably won’t have to stop showering this summer. But the bad news is pretty bad: wildlife, and the forests it lives in, could be in trouble.
Q: Absent some massive spring storms, what will the lack of snow mean for Boulder and the rest of the region this summer? Are we in for severe drought? Wildfires? Possible rationing of water supplies?
A: Snow in the west is white gold. Snowmelt runoff provides somewhere on the order of 70% to 80% of usable water in the western U.S. Agriculture, energy, and domestic and municipal uses of water are all dependent on snowmelt runoff. Moreover, many of our ecosystem services are dependent on snowmelt, including the health of our forests — which are under stress from the mountain pine beetle epidemic — and sufficient water in streams during the hot summer months to maintain our blue ribbon trout fisheries. Much of the western U.S. is experiencing a below-normal snow year. Here in Colorado we were 72% of average in February, and only 62% of the snowfall at the same time last year. And it hasn’t snowed much since.
How much water becomes available from snowmelt runoff is obviously dependent on the amount of snowfall that we have. Less snowfall means less available snowmelt. However, the amount of usable water from snowmelt also depends on when the snow melts. For the same amount of snowfall, the earlier that snowmelt begins, the less available water compared to the same amount of snow but later snowmelt. The reason is that earlier snowmelt is caused by warmer air temperatures, and warmer air temperatures mean the vegetation wakes up earlier and more water is lost back to the atmosphere through evapo-transpiration. Here in the Front Range, snow has been melting for the last week at 10,000 feet at our Niwot Ridge LTER research site, a month ahead of schedule and two months ahead of last year.
The good news is that we expect little affect on water availability. Last year was an above-normal snow year with a late start to snowmelt. Thus, we had abundant flow in our streams and rivers, with excess water that was stored in reservoirs. This stored water from last year will in general be adequate to offset this year’s low flows. However, our reservoir storage is only adequate for about 2 years. Several consecutive years of low snow results in a tipping point where reservoirs storage can no longer compensate for the low snow, and water availability declines rapidly, as happened in the drought in Colorado from 2000 to 2002.
The low snow year will likely have its largest affect on vegetation that depends on snowmelt as an important source of soil moisture — our forests. A reduction in available soil moisture results in water stress for our forests, making them more vulnerable to attack from the mountain pine beetle and other insects. If the current climate conditions continue, we may see a renewed mortality of our forests from insect outbreaks. And obviously, the danger of grassland and forest fires increases dramatically because low soil moisture results in low fuel moisture, the most important ingredient for wildland fires.
Pikas are particularly at risk from the low snow year, for two reasons. Pikas are the cuddly rabbit-like critters that live in rock piles at high elevation, generally above timberline. Their presence is known to many high-elevation hikers by the characteristic whistle sound they make. Pikas are awake all winter; they don’t hibernate like marmots. Pikas need a thick snowpack to insulate their rock homes and keep them warm, a lot like a snow cave. A thin snowpack means that pikas will be much colder and can freeze to death during the winter. Secondly, pikas need to harvest enough food during the summer to last through the long winter. A low snow year means little soil moisture and a bad growing season for alpine tundra. So, there may not be enough forage for pikas to harvest to get them through the following winter.
The low snow year here in the Colorado Front Range will stress our water resources, but in general will be compensated by increased releases of water from reservoirs. The largest affect likely will be on the flora and fauna. There is a good chance that there will be increased mortality of our forest resource by insect outbreaks. The chances of more and larger wildfires are greatly increased. And our fauna, from pikas to elk, will be stressed by the poor forage year.
Pika photo credit: Chris Kennedy / USFWS (via Flickr)