Event Title

Soil Moisture Patterns on Conifer and Aspen Hillslopes in an Alpine Catchment of Northern Utah

Presenter Information

Amy Burke

Location

ECC 216

Event Website

https://water.usu.edu/

Start Date

3-31-2008 5:40 PM

End Date

3-31-2008 5:45 PM

Description

Conifer invasion has been considered a significant factor explaining the decline in the extent of aspen cover in Utah. A consequence of this change in vegetation type may be lower water yield from mountain headwater catchments in the region. In this study, soil moisture patterns and snow accumulation were compared between conifer and aspen dominated hillslopes to understand the differences in (1) the timing of surface water inputs from snow melt and (2) how the wetting front of these inputs travels through the soil profile vertically and laterally. Nested soil moisture probes were installed in the summer of 2006 on two hillslopes adjacent to a stream in a headwater catchment of the Ogden River basin. One transect of eight nests lies perpendicular to the stream in an aspen dominated stand and another in a conifer stand. Nests consist of three probes at 5, 20 and 100cm or as deep as we could install the probe (45 to 110cm). Peak snow water equivalent was measured along each of the transects at a 4m interval. Snow surveys revealed similar average snow water equivalents between aspen and conifer stands but a greater variability of snow pack in the conifer stand. Soil profiles under the two vegetation types were found to vary greatly with aspen having a deeper profile with a higher clay content and conifer having a shallow and extremely rocky profile. Hourly volumetric soil water contents showed that water inputs from fall precipitation did not penetrate to the deeper layers of the soil profiles (60 to 100cm) in either vegetation type. At 20cm depth, fall precipitation increased saturation to 30% in the conifer profiles and 60%, twice as much, in the aspen. These levels of saturation were sustained throughout the winter months after which peak soil moisture in the spring showed all depths reaching 90% or greater saturation in both vegetation types. Spring snow melt water saturated the entire profile and sensors at all depths reacted to melt water inputs. Peak soil moisture in the spring snow melt came earlier on the aspen hillslope, probably because of the high saturation level sustained over the winter. The study has shown that for most of the year water inputs remain in the soil profile and only during the spring snow melt is there a chance for percolation to deeper groundwater storage. Because the degree of saturation over the winter was greater in the aspen hillslope, the duration of peak soil moisture was greater in the aspen than in the conifer hillslope.

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Mar 31st, 5:40 PM Mar 31st, 5:45 PM

Soil Moisture Patterns on Conifer and Aspen Hillslopes in an Alpine Catchment of Northern Utah

ECC 216

Conifer invasion has been considered a significant factor explaining the decline in the extent of aspen cover in Utah. A consequence of this change in vegetation type may be lower water yield from mountain headwater catchments in the region. In this study, soil moisture patterns and snow accumulation were compared between conifer and aspen dominated hillslopes to understand the differences in (1) the timing of surface water inputs from snow melt and (2) how the wetting front of these inputs travels through the soil profile vertically and laterally. Nested soil moisture probes were installed in the summer of 2006 on two hillslopes adjacent to a stream in a headwater catchment of the Ogden River basin. One transect of eight nests lies perpendicular to the stream in an aspen dominated stand and another in a conifer stand. Nests consist of three probes at 5, 20 and 100cm or as deep as we could install the probe (45 to 110cm). Peak snow water equivalent was measured along each of the transects at a 4m interval. Snow surveys revealed similar average snow water equivalents between aspen and conifer stands but a greater variability of snow pack in the conifer stand. Soil profiles under the two vegetation types were found to vary greatly with aspen having a deeper profile with a higher clay content and conifer having a shallow and extremely rocky profile. Hourly volumetric soil water contents showed that water inputs from fall precipitation did not penetrate to the deeper layers of the soil profiles (60 to 100cm) in either vegetation type. At 20cm depth, fall precipitation increased saturation to 30% in the conifer profiles and 60%, twice as much, in the aspen. These levels of saturation were sustained throughout the winter months after which peak soil moisture in the spring showed all depths reaching 90% or greater saturation in both vegetation types. Spring snow melt water saturated the entire profile and sensors at all depths reacted to melt water inputs. Peak soil moisture in the spring snow melt came earlier on the aspen hillslope, probably because of the high saturation level sustained over the winter. The study has shown that for most of the year water inputs remain in the soil profile and only during the spring snow melt is there a chance for percolation to deeper groundwater storage. Because the degree of saturation over the winter was greater in the aspen hillslope, the duration of peak soil moisture was greater in the aspen than in the conifer hillslope.

https://digitalcommons.usu.edu/runoff/2008/Posters/21