Joint Rock Physics Inversion of Time-lapse ERT and Seismic Refraction to Map Porosity and Track Changes in Water Saturation on a Mountain Hillslope
Abstract
Mountain watersheds are important for water storage and streamflow generation in the western United States. The precipitation that falls as snow on mountain hillslopes drives streamflow, infiltrates the subsurface, and is ultimately the water that recharges downgradient aquifers. The goal of this study is to use seismic refraction and time-lapse electrical resistivity tomography (ERT) data to map porosity and track seasonal changes in water saturation on a mountain hillslope using a novel joint rock physics inversion. To achieve this, the seismic refraction and time-lapse electrical resistivity tomography data are used to produce a map of the change in water saturation and porosity on a 60 m hillslope. The change in volumetric water content was calculated, at each location in the subsurface, from the estimated porosity values and the corresponding water saturation change. To validate the inversion we used borehole nuclear magnetic resonance (NMR) measurements of volumetric water content. We found that the joint rock physics inversion predicted a smaller change in volumetric water content than the NMR measurements. Further adjustments to the rock physics inversion and the inputs may be able to produce a better map of porosity and water saturation. A valid model of water saturation variations and porosity is critical for predicting how water from melting snowpack infiltrates the subsurface and flows through or is stored in mountain watersheds to better inform water management decisions.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMNS41B0808S
- Keywords:
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- 0933 Remote sensing;
- EXPLORATION GEOPHYSICS;
- 1829 Groundwater hydrology;
- HYDROLOGY;
- 1835 Hydrogeophysics;
- HYDROLOGY;
- 1880 Water management;
- HYDROLOGY