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HYDROLOGIC AND GEOMORPHIC CONTROLS ON RIPARIAN ECOSYSTEMS IN THE GREAT BASIN OF CENTRAL NEVADA
Citation:
Jewett*, D G., M. L. Lord, J. R. Miller, AND J. C. Chambers. HYDROLOGIC AND GEOMORPHIC CONTROLS ON RIPARIAN ECOSYSTEMS IN THE GREAT BASIN OF CENTRAL NEVADA. Presented at Ecological Society of America Conference, Tucson, AZ, 08/09/2002.
Description:
Understanding surface and ground water flow system interactions is key to maintaining and restoring riparian and wet meadow ecosystems, especially in the Great Basin of central Nevada where they support the majority of the region's biodiversity. To better understand these interactions and the impacts of stream incision, two field sites were studied: Big Creek and Indian Creek; both are located in the Humboldt-Toyiabe National Forest. At the Big Creek site, a perennial stream traverses a wet meadow and connects upstream and downstream reaches of the axial channel. Ground-water flow is mostly in a downvalley direction through valley-fill sediments. Upstream, water is lost from the axial channel into the adjacent alluvium and vertical ground-water gradients are downward. As the wet meadow is approached, flow patterns are reversed and water is delivered to the channel from the surrounding alluvium. Waters within the wet meadow are likely derived from upwelling water moving downvalley through alluvial sediments that encounter a constriction in the aquifer. Ground-water flow is complicated by the complexity of the local stratigraphy and seasonal variability. In contrast to Big Creek, the Indian Creek valley wet meadow systems have been strongly altered by stream incision. Unincised headwater reaches contain broad, wet meadows that are reduced to narrow, strip wet meadows downstream where the valley floor has been incised up to 3 m. In the incised region, the upstream reach contains a perennial stream, a ground-water system with minimal temporal variability, and a strip wet meadow. Downstream in the incised reach, willows and dry meadow species flank an ephemeral, cobble-bedded channel, and the ground-water system exhibits high spatial and temporal variability. Analysis of plant communities at over 100 ground-water wells at both study sites show that the location and success of plant communities is sensitive to depth to ground water. For example, wetland plants dominate where the water table is near the land surface and sagebrush dominates where the depth to water exceeds a few meters. Study results from both sites show that these wet meadow systems are dynamic and sensitive; a thorough understanding of these systems is necessary to entertain the concept of ecosystem management and restoration.