It’s that time of year when snowpack turns into streamflow. Sounds like a coach turning into pumpkin but it’s very much the opposite and more important than that. A previous blog discussed the importance of the April 1st snowpack as measurement of our summer water reservoir. April 1st is traditionally viewed as the day on which snowpack, in this case snow water equivalent, measures at its maximum. Note that the day can be a bit of a “moving target” that depends on weather, volume of snow, and geographical location. The maximum day can be a few days before or after.
Snowmelt can be a long process, with patches of snow lingering on the mountains well into summer. But those who pay close attention to spring will tell you that the season as a whole seems be happening earlier than it has been. It’s not nostalgia. Scientists studying historical records of streamflow at gaged sites observe that spring snowmelt is starting about one to three weeks earlier in 73% of mountainous basins across the west. Another way that scientists measure the start of spring is by noting the date that certain flowers bloom, for instance honeysuckle and lilac. In the western US, these flowers are blooming about a week earlier than they have been over the course of record-keeping.
This year at the Mt Rose snotel, the maximum snow water equivalent was 23.9 inches and measured on March 25, 26, and 27. After that, the snow started to melt. The chart below is downloaded from the National Resources Conservation Service (NRCS) interactive website. Look for the black line, that is 2021 snow water equivalent and peaks just above 20 inches at the end of March. As discussed in a previous blog, the snowpack is low this year as compared with the average, which is a green line.
What does this mean? If you are counting ski, snowshoe, or sled days, there are not many left. Get out and enjoy the last little bit of winter.