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Rain, Snow, and the Soil Moisture Situation

March 08, 2016

While Aspen and the high country enjoyed a dusting of snow over the weekend, lower elevations in Basalt, Carbondale, and Glenwood Springs instead just felt a deluge of cold rain. In a semi-arid state like Colorado, any type of precipitation usually seems like a good thing, but whether that precipitation comes in the form of rain or snow can make a difference to ecosystem conditions that lasts throughout the growing season.

Each spring since the iRON stations have been installed, they show sudden peak in soil moisture as snow cover melts and as the ground thaws out. Depending on the elevation of the individual station and the snowpack and temperatures we have had over the winter, these spikes in soil moisture usually occur somewhere between mid-March and mid-April. Once this "spring soak" has occurred, soil moisture at the iRON sites tend to follow a general trend decline, with only small spikes in moisture increase, until mid to late summer, when heavy intensity rain storms of over 0.8inches of rain in a single day help to recharge soil moisture all the way down to a 20 inch depth. The graph below shows an example of the patterns of soil moisture shown at the Sky Mountain station from its installation through the present.

Other, lower elevation stations, such as the one at Glenwood Springs may show an earlier date of soil saturation. This is the first winter/spring transition for which there has been a station at Glenwood Springs, so we are unable to compare it to other years, but an increase in soil moisture at all three depths: 2in, 8in, and 20in (5, 20, and 51 cm) had already began around February 14th this year, which a sharper spike in soil moisture increase on February 18th. As our data record grows will be able to compare dates of soil thaw, periods of warm winter temperatures, and rain events to soil moisture in order to better understand the interplay between these factors.