Transient Electrokinetic Signals Measured above a Fractured Rock Aquifer
Abstract
We consider the transient self-potential (SP) signals associated with groundwater and soil biophysics processes in and above a confined fractured rock aquifer. Thesignals may be attributed to diurnal thermal fluxes, seismicity , earth tides, groundwater flow, and soil moisture redistribution. They arise due to the existence ofthe electrostatic double layer at the mineral-water interface and flow of water in the pore-space. The aquifer in this study is a shallow confined fracturedsandstone formation bounded above by a clayey aquitard with an average thickness of 11 m, and below by meta-volcanic bedrock. To measure the transient self-potential signals, 16 non- polarizable Copper/Copper Sulphate ( C u / C u S O 4 ) were installed at a depth of 1 m from ground surface in a bentonite paste in augered holes. A depth of 1 m was chosen to minimize the effect of diurnal thermal fluctuations. The electrodes were installed at radial intervals of 2 m from a monitoring wellthat partially penetrates the aquifer. The aquifer was also instrumented with 1-inch diameter piezometers at radial intervals of 10 m, to continuously monitoraquifer groundwater fluctuations. We present results of passive water-level and SP monitoring, as well as the transient SP response to constant-rate pumping testsconducted in the monitoring well. The fractured rock aquifer is conceptualized as a dual-porosity and a semi- analytical solution predicting the transient SPresponse due to groundwater flow toward a pumping well is also presented. The results of the work shows that SP signals and models are useful for characterizingfractured rock aquifers.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H11D..02M
- Keywords:
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- 1829 Groundwater hydrology;
- HYDROLOGY;
- 1835 Hydrogeophysics;
- HYDROLOGY;
- 1865 Soils;
- HYDROLOGY;
- 1899 General or miscellaneous;
- HYDROLOGY