Measuring Groundwater Storage Potential in Mountain Meadows using Geophysical Methods at Red Clover Meadow Complex, Sierra Nevada, CA

Abstract:

ABSTRACT The Dotta Canyon meadow, located in the Red Clover Meadow complex, upper Feather River Watershed, Plumas County, California, was studied to measure sediment volume and groundwater storage capacity in this mountain meadow environment. Groundwater resources in mountain meadows play an important role in providing baseflow to local stream systems during dry summer months. Degraded meadows reduce baseflow contributions to local streams throughout the year impacting the local flora and fauna and water resources downstream. Groundwater storage potential of meadows is a function of the total volume of meadow sediments, the types of sediment present and the effective porosity of those materials. Assessing these properties in meadows is difficult though as meadow environments are commonly sensitive to investigative disturbances like drill rigs and backhoes. We applied seismic refraction techniques to measure the thickness of meadow sediments in the 8.3 km² Dotta Canyon. Specifically we conducted 42 seismic surveys, utilizing forward and reverse profiles to create a depth to bedrock isopach map of the Dotta Canyon meadow. Using ArcGIS software, aerial photographs and field GPS data to measure and calculate the meadow area and limited hand augering, we were able to calculate the volume of sediment in the meadow to be about 2.5E7 cubic meters. Hand augering in the meadow produced a record of meadow stratigraphy and helped determine appropriate locations for the collection of representative core samples. Representative cores were processed for effective porosity using the water porosimetry method. A mean effective porosity of 38%.was applied to volumetric calculations with results suggesting a groundwater storage capacity of 9.4E6 cubic meters.