HYDROGEOLOGIC SETTING AND CHARACTERISTICS OF RIPARIAN MEADOW COMPLEXES IN THE MOUNTAINS OF CENTRAL NEVADA: A CASE STUDY

Riparian wet meadow complexes in the mountains of the central Great Basin are scarce, ecologically important systems threatened by stream incision. An interdisciplinary team from government and academia is investigating the origin, setting, and biological--physical interrelationships of the meadows. The Kingston Canyon meadow complex, located in the Toiyabe Range, has been the focus of an intense research, monitoring, and restoration studies. This work has yielded data on groundwater levels from 100 wells along 10 transects from shallow (~0.5 m) to deep (~8 m) piezometers; lithology, grain size distribution, and organic content from 12 sediment cores; hydraulic conductivity of key hydrostratigraphic units; stream discharge; groundwater and surface water chemistry; seismic and ground penetrating radar cross-sections; vegetation classifications; stream water-stream bed temperature patterns; and stream morphology and profiles.

Valley geomorphology and geophysical data suggest that the meadow is bound by faults. The interplay of faults and up to 30 m of alluvial fill, from a mix of axial valley streams and side-valley alluvial fans, has created a setting that collects and detains groundwater to support the meadow; the meadow terminates downstream where unconfined, high hydraulic conductivity layers permit rapid draining and lowering of the groundwater table. Artesian conditions are common in the meadow because of the complex stratigraphy with strongly contrasting hydraulic conductivities (10^-2 – 10^-5 cm/s) and high gradients. Groundwater level and streambed temperature survey data show the meadow is located a groundwater discharge area. Calcium-bicarbonate type waters reflect source areas and relative contributions of downvalley versus side-valley inputs. Vegetation patterns strongly correlate with depth to groundwater; sage brush dominates at wet meadow margins and adjacent to the incised Kingston Creek whereas Nebraska sedge is dominant along valley sides where the groundwater table is less than 0.5 m deep. The knowledge from this and other study sites will be used to provide a scientific basis for management, prioritization, and restoration for similar riparian meadows throughout the Great Basin. (This abstract does not necessarily reflect EPA policy or views.)