Year of Award

2006

Document Type

Professional Paper

Degree Type

Master of Science (MS)

Other Degree Name/Area of Focus

Geology

Department or School/College

Department of Geosciences

Committee Chair

William Woessner

Commitee Members

Joel Harper, Steven Running

Keywords

Biome-BGC, block, ecohydrology, ecosystem, ground water, groundwater, hydrogeology, MBR, model, MODFLOW, Montana, mountain, mountain-block recharge, MT-CLIM, process, recharge, water balance

Abstract

Magruder, Ian, M.S., December 2006 Geology Evaluation of an Ecohydrologic-Process Model Approach to Estimating Annual Mountain-Block Recharge Chairperson: Dr. William Woessner Regional subsurface mountain-block recharge (MBR) is viewed as a key component of basin aquifer systems found in semi-arid environments. Yet water resource managers do not have a commonly available and reasonably invoked quantitative method to constrain possible MBR rates. Recent advances in landscape-scale ecohydrologic process modeling offer the possibility that weather, climate, and land surface physical and vegetative conditions can be used to estimate MBR. We present an approach that uses remotely sensed physiographic data to model a mountain water balance including the component of MBR. In this approach, we evaluate the ecosystem process model Biome-BGC (Running and Hunt, 1993; Thornton et al., 2002), used in tandem with the mountain climate simulation program MT-CLIM (Running et al., 1987; Kimball et al.,1997; Thornton and Running, 1999), to calculate the annual MBR within a 24,600 ha watershed. The modeling tool is also used to investigate how climatic and vegetative controls influence recharge dynamics along the basin-mountain physiographic gradient. Our work estimated mean annual MBR flux in this crystalline bedrock terrain to be 99,000 m3/d or approximately 19% of annual precipitation. Data analyses indicate that vegetative control on soil moisture flux is significant only at lower elevations and snowmelt is the only significant annual recharge source occurring on a macroscale in this environment. Results also demonstrate that evapotranspiration (ET) is radiation limited in wet years and moisture limited in dry years, and consequently potential recharge to groundwater is significantly higher during wet climate cycles. The application of ecohydrologic modeling to estimate MBR shows promise for modeling MBR at the mountain-scale. However, future efforts will need to incorporate a more advanced understanding of mountain recharge processes and refined ability to simulate those processes at varying and appropriate scales.

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© Copyright 2006 Ian Auguste Magruder