Snowpack Update and Outlook: March 2020
Rather than climbing snowbanks onto the Pagosa Springs High School roof or jumping out of the second-story classroom windows into the snow, the high school track team finished its 2nd week of training on a snow-free track, and girls soccer and boy’s baseball are practicing on the fields instead of the high school parking lot. The rapid melt of the low elevation snowpack is great news for spring sports, but not so good from a water supply perspective. The meager snow deposits during January, February, and early March have erased our December reserves, causing the Upper San Juan Snotel site to drop below the norm for this time of year.
February is usually our 2nd biggest snow month, but only 1.9 inches of water accumulated at the Upper San Juan Snotel Site, which is 30% of normal for the month. Currently, the Upper San Juan Snotel Site is 76% of normal, which equates to a 6.5-inch water deficit. There are 20.2 inches of water frozen in the 55-inch snowpack. The Wolf Creek Summit snotel site is faring slightly better at 83% of normal with 4.5 inches of missing water in the 62-inch snowpack. I usually focus on snowpack numbers from the Upper San Juan Snotel Site because the site has a longer period of record (back to 1935) and it’s located at an elevation that is closer to the mean watershed elevation making it more representative of the Upper San Juan River watershed as a whole.
Historically, March is our 3rd-biggest snow producer, but with the exception of last year, March snow accumulation is trending downward and is approaching the point where we lose more snow in March than we gain. As shown in the graph below, March used to be a big snow producer in the 1980s and 1990s, but March snow accumulations have gradually decreased by 0.2 inches of water per year or 2 inches of water per decade at the Upper San Juan Snotel Site.
Last spring, I had my high school global science students collectively analyze the March snowfall trends (1979-2019) for 53 Colorado snotel stations. We wanted to discover how March snow accumulation was trending statewide. We found that over the past 40 years, March snow accumulations have decreased in each of the state’s major river basins (averaging -0.07 inches of water per year). The trend reveals that we're likely receiving less snow in March, melting more snow in March, or a combination of both. We also found that the northern watersheds (North and South Platte, Upper Colorado, which are mostly blue and green on the map) are faring better than the southern watersheds (Gunnison, Arkansas, Rio Grande, and Upper San Juan, which are mostly yellow, orange and red on the map). The Upper San Juan and Rio Grande watersheds have the steepest downward trend in March (-0.1 inches of water per year).
Out of the 53 stations we analyzed, the Upper San Juan Snotel Site had the steepest downward trend (-0.2 inches of water per year). Had 2019 not been such a positive outlier, the trendline would be even steeper (-0.26 inches per year). Hopefully, March 2020 will buck the trend like March 2019. The short-term weather forecast indicates the potential for moisture so hopefully, the storms will track in our direction and we can resume building our high elevation snowpack so we can avoid drought conditions this summer.