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GROUND WATER/SURFACE WATER INTERACTIONS IN A GREAT BASIN WET MEADOW ECOSYSTEM
Citation:
Jewett*, D G. AND J. R. Miller. GROUND WATER/SURFACE WATER INTERACTIONS IN A GREAT BASIN WET MEADOW ECOSYSTEM. GSA Annual Meeting & Exposition, Reno, Nevada, 11/8-18/2000.
Description:
Riparian corridors within upland watersheds of the Great Basin locally contain wet meadow ecosystems that support much of the region's biodiversity. Plant communities in these riparian and wet meadow ecosystems can be highly dependent on the depth to and fluctuations in the water table. Ground water and surface water are intimately linked in these environments and their interactions play a key role in maintaining riparian and wetland vegetation.
Interactions between surface water and ground water flow systems were examined at the Big Creek field site, in the Toiyabe Mountains in central Nevada, which is though to be representative of wet meadow ecosystems in the area. Like many of the Great Basin wet meadows, the Big Creek site is positioned upstream of a valley constriction created by an alluvial fan. A perennial stream traverses the site and several small springs emerge and flow across the meadow which is wet during the majority of the year. The site was instrumented with 54 piezometers and 7 monitoring wells to measure water table depths and observe ground water flow patterns. Instream discharges also have been measured along several reaches of the stream.
Ground water flow patterns indicate that the stream is a losing system upgradient of the site. As the stream approaches the wet meadow it becomes a gaining system. Data from nested piezometers also exhibit downward gradients in the upstream portion of the site and upward gradients in the wet meadow. Stream discharge measurements confirm the ground water data. The extent to which ground water recharge and discharge occur is directly related to local weather, that is wet versus dry seasons. Ground water flow patterns and preliminary geochemical and seismic results suggest that the ground water supplying the meadow is moving downvalley through the alluvial fill and is forced to the surface by constrictions in width and /or thickness of the alluvial aquifer.