Your Watershed: Mitchell helps us know our snow
Liza Mitchell, Education and outreach coordinator for the Roaring Fork Conservancy and board member for the Middle Colorado Watershed Council, gave a talk recently at the Sustaining Colorado Watersheds Conference in Avon.
She and collaborator Jeff Derry, director of the Center for Snow and Avalanche Studies in Silverton, spoke to the benefits, limitations and areas of improvement for snow data collection and what it means for water managers and our water supply.
As winter sets in in Garfield County, it is important to remember that snow is essential not only to our recreation, but also for our daily water use. I spoke with Liza Mitchell about her recent presentation, and what we should understand about snow.
AW: Tell me a little about why you spoke about snow at a water conference.
LM: There is a lot of focus in the Colorado Water Plan and across the state on improving efficiencies (water conservation and irrigation practices) and increasing storage (building new reservoirs). Both of these address water supply, but we also need to focus on where this water is ultimately coming from, and that source is snowpack.
Last winter, I went to a snow science course in Silverton put on by Jeff Derry and the Center for Snow and Avalanche Studies, and there was an incredible mix of water professionals there. What I noticed was that across very diverse professions, there was a common interest in better understanding snow as the driver of our water supply. Water managers are making decisions based on water supply forecasts, and those forecasts are based on the amount of snow we have, and the snow science behind it.
AW: Last year, I spoke with you about SnoTel sites for a Post Independent article. How do SnoTel sites play into the conversation about water supply?
LM: SnoTel sites collect information on snowpack accumulation and that data is the backbone of the most water supply forecasts, so they are incredibly important part of the conversation. Snow accumulation, and the amount of water held within that snowpack, is really helpful information, but it has limitations.
For example, one thing SnoTel sites can’t tell us is how snowpack varies across space. Snow accumulates differently across steep complex terrain, in heavily forested areas, and in windy treeless areas. SnoTel sites are established in permanent locations, so the data is valuable for year-to-year comparisons, but for calculating basinwide snow water equivalent, it may be a bit lacking.
SnoTel sites are also located in a fairly narrow elevation band, about 8,000-10,000 feet, so the network doesn’t capture snow conditions at higher elevations.
Finally, SnoTel sites aren’t equipped to measure solar radiation, which is the primary driver of snowmelt.
Understanding the limitations of SnoTel data is crucial to our ability to make reliable runoff predictions and water management decisions.
AW: You mention solar radiation, I have heard this before in regards to increasing the rate of snowmelt, but is radiation different than heat from the sun?
LM: Yes, solar radiation is the actual energy that the sun gives off, not the temperature we feel on any given day, and it is the radiation that really drives snowmelt in Colorado. Weather, like clouds, can decrease the solar radiation that hits the snow and slow down snowmelt. However, what snow scientists are noticing is that when dust gets in the snow, this dust absorbs more of the sun’s radiation, which increases snowmelt.
AW: If the snow melts, it just runs into the river, so why does increasing snowmelt rate matter to water managers?
LM: Information collected from SnoTel sites helps water forecasters predict the amount of water within the snowpack, but does not help much when it comes to timing. The timing of snowmelt determines when streams and rivers hit peak runoff and how long high flows might last, which has implications for many sectors of society: consider the decisions that go into irrigation for farmers and ranchers, recreational industries like fishing and whitewater rafting, flood mitigation and planning, maintaining reservoir levels, and public safety.
Annie Whetzel is the Community Outreach Coordinator at The Middle Colorado Watershed Council. To learn more about the MCWC, go to http://www.midcowatershed.org. You can also find them on Facebook at http://facebook.com/midcowatershed. To learn more about SnoTel sites, and snow science, check out the Roaring Fork Conservancy’s website for their annual winter SnoTel snowshoe hike, and check out Center for Snow Science’s website for the upcoming winter snow science course for water managers.