Andrea Thorstensen presenting results at ESRL in Boulder, CO (Photo credit: Barb DeLuisi, NOAA)

Hollings Scholar Completes Comparative Analysis of Soil Moisture in California's American River Basin

An analysis of the North Fork (NF) of the American River Basin's soil properties and drainage characteristics was conducted by Andrea Thorstensen (NOAA Hollings Scholar) and Robert Zamora (NOAA Earth System Research Laboratory) using soil moisture data collected by the NOAA Hydrometerology Testbed Soil Moisture Network. Andrea is a senior at St. Cloud State University in Minnesota, and spent her summer in Boulder working on the analysis. She intends to pursue interdisciplinary graduate studies in hydrology and meteorology.

Their work found that the soils in the upper NF Basin appear to dry down much more quickly than those in the lower basin following snowmelt or the last significant rain event before the dry season. During the wet season prior to the dry down, the upper basin received more precipitation than the lower basin, yet the lower basin retained more moisture and for longer periods of time. The elevation where the most precipitation fell during the wet season coincides with the area of the basin where soils transition from clay to more alluvial and volcanic soils.

Climate change scenarios suggest that more precipitation will fall as rain rather than snow at higher basin elevations in the future. This implies that more precipitation may fall on soils that are less capable of retaining water, thus increasing the flood risk to an already vulnerable area as more water enters the North Fork of the American River more quickly. Andrea presented these results during the NOAA Student Symposium held the first week of August in Silver Spring, MD.