Spatial Survey of Surface Soil Moisture in a Sub-alpine Watershed Katherine E. Williams M.S. GISc Candidate Department of Geography, University of Denver October 7, 2010
Purpose 2
Introduction to Soil Moisture 3 Used with permission: Kampf, Stephanie. Sensitivity of soil moisture to terrain and snow cover. Colorado State University. Presentation. 2010.
Hillslope Measurement Summary Point Soil Moisture: Locally variable, no apparent relationship to snow distribution Hillslope Flow: Shallow lateral downslope flow during snowmelt Exfiltration at bedrock and topographic breaks Catchment Response: Exfiltration Rapid pathways for melt to reach streams Neither moisture distribution nor runoff source regions would be predicted by most catchment-scale hydrologic models Soil moisture trends on a hillslope transect Exfiltration at topographic breaks 4 Used with permission: Kampf, Stephanie. Sensitivity of soil moisture to terrain and snow cover. Colorado State University. Presentation. 2010.
Study Area: Loch Vale, RMNP Thatchtop Sky Pond Taylor Peak Soil Moisture Study Area Boundary Hillslope Transects The Loch Elevation: 3097-4009 m Areal Size: 690 ha 5
Research Questions How is soil moisture distributed in space? What geostatistical approach best predicts this distribution? How do local, physical attributes (specifically elevation, slope, aspect, and vegetation type) affect soil moisture distribution? Which variable or combination of variables best predicts soil moisture distribution? 6
Research Plan Overview Field Survey -GPS Coordinates -Land Cover Type -Soil Moisture Soil Temperature -Digital Photographs Lidar -Elevation -Slope -Aspect -Top of Canopy Imagery -High Resolution Land Cover Spatial Analysis -Data Exploration -Spatial Statistics -Hypothesis Testing Maps -Soil Moisture Surface -Land Cover Classification Conclusions -Interpolation Method Comparison -Soil Moisture Distribution and Relationship with Local Terrain 7
Sampling Plan Pre-sampling Considerations Local Variability of Soil Moisture Temporal Variability Collection Practicality Geostatistical requirements Stratified random target points (cover range of variables) 15 soil moisture measurements at center and in four cardinal directions Sample late in the summer (drained basing) At least 120 GPS positions at center of sampling point Vegetation type, percent ground cover, percent canopy cover, photo(s) of site 8
Field Implementation August 9-11, 2010 Collected 111 points throughout study area 9
Post-processing GPS points: Differential Correction Average horizontal precision ~ 5 meters Data entry & organization Visual inspection between soil moisture and independent variables 10
Soil Moisture & Elevation 11
Soil Moisture & Aspect 12
Soil Moisture & Slope 13
Soil Moisture & Vegetation Type 14
Next Steps Finish GPS post-processing Vegetation Map Image classification Data Analysis Geostatistics 1 meter DEM Airborne Lidar 15
Acknowledgements Advisors: Dr. Sharolyn Anderson (DU), Dr. Stephanie Kampf (CSU), & Dr. Hillary Hamaan (DU) Field Crew: DU Dr. Sharolyn Anderson, Joseph Hoover, Dr. Paul Sutton, & Brenton Wonders CSU Dr. Jill Baron, Sean Jacobson, Cara Moore, Brooke Osborne, Ben Reynolds, Eric Richer, & Julia Spencer National Park Service: Judy Visty & Jeff Conner 16
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Variables and Data Sources Independent Elevation (10 Meter DEM, NPS; Lidar ~0.7 Meter DEM, Grand County, CO) Slope (Derived from DEM) Aspect (Derived from DEM) Vegetation Type (NPS survey; 1 ft Vis-NIR USFS image) Dependent Soil Moisture (Field Collection) 18
Field Implementation August 9-11, 2010 Field Teams collected 111 samples points Wet conditions Equipment function Mobility 19