HR: 0800h
AN: H21A-0168    [Abstracts]
TI: Topographic Controls on Hillslope–Riparian Water Table Continuity in a set of Nested Catchments, Northern Rocky Mountains, Montana
AU: * Jencso, K G
EM: kelsey.jencso@myportal.montana.edu
AF: Montana State University, Watershed Hydrology Laboratory, Dept. of Land Resources and Envrionmental Sciences, 334 Leon Johnson Hall, Bozeman, MT 59717, United States
AU: McGlynn, B L
EM: bmcglynn@montana.edu
AF: Montana State University, Watershed Hydrology Laboratory, Dept. of Land Resources and Envrionmental Sciences, 334 Leon Johnson Hall, Bozeman, MT 59717, United States
AU: Gooseff, M N
EM: mgooseff@engr.psu.edu
AF: Penn State University, Civil & Environmental Engineering Department, 212 Sackett Bldg., University Park, PA 16802, United States
AU: Wondzell, S M
EM: swondzell@fs.fed.us
AF: U.S. Forest Service, Pacific Northwest Research Station, Olympia Forestry Sciences Lab, 3625 93rd Ave SW, Olympia, WA 98512, United States
AU: Bencala, K E
EM: kbencala@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, United States
AU: Payn, R A
EM: rpayn@mines.edu
AF: Colorado School of Mines, Department of Geology and Geological Engineering, 1516 Illinois St., Golden, CO 80401, United States
AB: Understanding how hillslope and riparian water table dynamics influence catchment scale hydrologic response remains a challenge. In steep headwater catchments with shallow soils, topographic convergence and divergence (upslope accumulated area-UAA) is a hypothesized first-order control on the distribution of soil water and groundwater. To test the relationship between UAA and the longevity of hillslope-riparian-stream shallow groundwater connectivity, we quantified water table continuity based on 80+ recording wells distributed across 24 hillslope-riparian-stream cross-sections. Cross-section upstream catchment areas ranged in size from 0.41 to 17.2 km², within the Tenderfoot Creek Experimental Forest (U.S. Forest Service), northern Rocky Mountains, Montana, USA. We quantified toe-slope UAA and the topographic index (TI = ln a/tanβ) with a Multiple-D- Infinity (area routing in multiple infinite downslope directions) flow accumulation algorithm analysis of 1, 3, 10, and 30m ALSM derived DEMs. Indices derived from the 10m DEM best characterized subsurface flow accumulation, highlighting the balance between the process of interest, topographic complexity, and optimal grid scale representation. Across the 24 transects, toe-slope UAA ranged from 600-40,000 m², the TI ranged from 5-16, and riparian widths were between 0-60m. Patterns in shallow groundwater table fluctuations suggest hydrologic dynamics reflective of hillslope-riparian landscape setting. Specifically, correlations were observed between longevity of hillslope-riparian water table continuity and the size of the UAA (r²=0.84) and its topographic index (r²=.86). These observations highlight the temporal component of topographic-hydrologic relationships important for understanding threshold mediated hydrologic variables. We are working to quantify the characteristics and spatial distribution of hillslope-riparian sequences and their water table dynamics to temporally link runoff source areas to whole catchment hydrologic response.
DE: 1820 Floodplain dynamics
DE: 1826 Geomorphology: hillslope (1625)
DE: 1839 Hydrologic scaling
DE: 1879 Watershed
SC: Hydrology [H]
MN: 2007 Fall Meeting