QUANTIFYING THE SPATIO-TEMPORAL VARIABILITY OF SUBSURFACE FLOW ACROSS THREE HILLSLOPES IN A SEMI-ARID, ALPINE FOREST

Author

Emily N. Clark, College of ForestryFollow

Year of Award

2015

Document Type

Thesis

Degree Type

Master of Science (MS)

Other Degree Name/Area of Focus

Forest Management

Department or School/College

College of Forestry and Conservation

Committee Chair

Kelsey Jencso

Commitee Members

James Riddering, Marco Maneta

Abstract

Distinguishing watershed characteristics that influence the spatial and temporal response of shallow subsurface flow within hillslopes is requisite for quantifying streamflow quantity, timing, and quality. I evaluated local and non-local (upslope) topographic influences on shallow water table development, magnitude, and spatial extent across 3 hillslopes (24 shallow groundwater recording wells) of distinct shape and size in the Lubrecht Experimental Forest, MT. I asked the question: at what spatial and temporal scales do characteristics of surface topography (upslope or local) govern shallow groundwater response and runoff contributions to streams? My results corroborate prior findings of the role upslope accumulated area (UAA) and local slope play, but emphasize the importance of considering the two variables independently. Increasing UAA generally resulted in greater duration of saturation across each study hillslope (R²= 0.78; p < .05). Local slope was a significant predictor of mean water table height (R²= -0.86; p < .05). Combined as the topographic wetness index, both local (slope) and non-local drainage area described the propensity for shallow groundwater duration and magnitude (R²= .72; p < .05). We used this relationship to quantify the spatio-temporal variability of hydrologically connected contributing area across the 3 study sites. The spatial extent and timing of hydrologically connected contributing area was synchronized with changes in stream reach discharge adjacent to each hillslope contributing area. These relationships suggest that the organization of hillslope topography is a necessary context and consideration for predicting runoff source contributions to streams in space and time.

Recommended Citation

Clark, Emily N., "QUANTIFYING THE SPATIO-TEMPORAL VARIABILITY OF SUBSURFACE FLOW ACROSS THREE HILLSLOPES IN A SEMI-ARID, ALPINE FOREST" (2015). Graduate Student Theses, Dissertations, & Professional Papers. 4448.
https://scholarworks.umt.edu/etd/4448