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HYDROLOGY OF CENTRAL GREAT BASIN MEADOW ECOSYSTEMS – EFFECTS OF STREAM INCISION
Citation:
LORD, M., D. G. JEWETT, J. MILLER, D. GERMANOSKI, J. CHAMBERS, W. TROWBRIDGE, K. STURTEVANT, AND G. BAKER. HYDROLOGY OF CENTRAL GREAT BASIN MEADOW ECOSYSTEMS – EFFECTS OF STREAM INCISION. Presented at 2007 International Meeting of the Society for Range Management, Reno, NV, February 12 - 16, 2007.
Impact/Purpose:
To inform the public.
Description:
Riparian wet meadow complexes in the mountains of the central Great Basin are scarce, ecologically important systems that are threatened by stream incision. Our interdisciplinary group has investigated 1) the interrelationships of geomorphology, hydrology, and vegetation; and 2) the hydrologic and vegetative response to stream incision. Four detailed study meadows with years of instrumentation data and dozens of meadows with reconnaissance-level data support this research. Information from detailed sites includes data on groundwater (60-100 wells per site), surface water (gauging, temperatures), channel cross sections, geomorphology, stratigraphy (dozens of cores), geophysics (seismic and GPR), and vegetation. Meadows are present in groundwater discharge zones with high flow rates that are geologically controlled to maintain high groundwater tables. Most meadows in the mountains of the central Great Basin are actively being degraded, or are sensitive to degradation, caused by channel incision due to entrenchment of existing channels, groundwater sapping and piping, or avulsion. Meadow response to incision is, in general, a drop in the groundwater table followed by a consequent decrease in wet meadow vegetation composition and distribution. Specific responses to incision, however, vary from a negligible change in the groundwater water table, hydrogeomorphic processes, and distribution of wet meadow species to a complete loss of wet meadow species caused by a breach of the hydrologic conditions necessary to support the meadow. The type and magnitude of response of a meadow ecosystem to incision varies as a function of the source and flow direction of the groundwater, the stratigraphy and hydraulic conductivity of the alluvium underlying the meadows, the distribution and connectivity of aquifers supporting the meadows, groundwater-stream water interaction, the processes of incision, and the geomorphic setting. To best prioritize and choose management strategies for meadows threatened by incision requires understanding the spatial and temporal hydrologic complexities characteristic of these systems.