scholarly journals Technical Note: Disentangling the groundwater response to Earth and atmospheric tides to improve subsurface characterisation

2020 ◽  
Author(s):  
Gabriel C. Rau ◽  
Mark O. Cuthbert ◽  
R. Ian Acworth ◽  
Philipp Blum
Keyword(s):  
Rapid Assessment ◽  
Earth Tide ◽  
Technical Note ◽  
Previous Method ◽  
Earth Tides ◽  
Atmospheric Tides ◽  
Specific Storage ◽  
Novel Approach ◽  
Groundwater Response ◽  
Pressure Record

Abstract. The groundwater response to Earth tides and atmospheric pressure changes can be used to understand subsurface processes and estimate hydraulic and hydro-mechanical properties. We develop a generalised frequency domain approach to disentangle the impacts of Earth and atmospheric tides on groundwater level responses. By considering the complex harmonic properties of the signal, we improve upon a previous method for estimating barometric efficiency (BE) estimation while simultaneously assessing system confinement and estimating hydraulic conductivity as well as specific storage. We demonstrate and validate the novel approach using an example barometric and groundwater pressure record with strong Earth tide influences. Our method enables improved and rapid assessment of subsurface processes and properties using standard pressure measurements.

scholarly journals Technical note: Disentangling the groundwater response to Earth and atmospheric tides to improve subsurface characterisation

2020 ◽  
Vol 24 (12) ◽  
pp. 6033-6046
Author(s):  
Gabriel C. Rau ◽  
Mark O. Cuthbert ◽  
R. Ian Acworth ◽  
Philipp Blum
Keyword(s):  
Rapid Assessment ◽  
Earth Tide ◽  
Technical Note ◽  
Previous Method ◽  
Earth Tides ◽  
Atmospheric Tides ◽  
Specific Storage ◽  
Novel Approach ◽  
Groundwater Response ◽  
Pressure Record

Abstract. The groundwater response to Earth tides and atmospheric pressure changes can be used to understand subsurface processes and estimate hydraulic and hydro-mechanical properties. We develop a generalised frequency domain approach to disentangle the impacts of Earth and atmospheric tides on groundwater level responses. By considering the complex harmonic properties of the signal, we improve upon a previous method for quantifying barometric efficiency (BE), while simultaneously assessing system confinement and estimating hydraulic conductivity and specific storage. We demonstrate and validate this novel approach using an example barometric and groundwater pressure record with strong Earth tide influences. Our method enables improved and rapid assessment of subsurface processes and properties using standard pressure measurements.

A new Python package to estimate hydraulic and poroelastic groundwater properties using standard pressure records

2021 ◽  
Author(s):  
Gabriel Rau ◽  
Daniel Schweizer ◽  
Chris Turnadge ◽  
Philipp Blum ◽  
Todd Rasmussen
Keyword(s):  
Earth Tide ◽  
Barometric Pressure ◽  
Earth Tides ◽  
Specific Storage ◽  
Geomechanical Properties ◽  
Groundwater Response ◽  
Barometric Efficiency ◽  
Standard Pressure ◽  
Pressure Changes ◽  
Python Package

<p>Determining subsurface hydraulic and geomechanical properties crucially underpins groundwater resource investigation and management. While standard practice relies on active testing, passive approaches require less effort and cost but are underutilised. We present the new Python package named HydroGeoSines (HGS) which quantifies hydraulic and poroelastic subsurface properties using the groundwater response to natural forces (such as Earth tides and atmospheric pressure changes) embedded in standard measurements. All implemented methods are drawn from the peer-reviewed literature. The package includes basic handling of time series, such as joining and aligning records and handling gaps. HGS uses standard atmospheric and groundwater pressure records to estimate the Barometric Response Function (BRF) groundwater state of confinement, hydraulic conductivity, specific storage, barometric efficiency (BE) and porosity. If Earth tides are required, they can be calculated on-the-fly using the PyGTide package which is based on ETERNA and included. HGS allows easy compensation and correction of pressure or hydraulic heads from barometric pressure or Earth tide influences. Further, HGS includes import from and export to common data formats as well as visualisation of data and results. We demonstrate the use of HGS using example datasets from around the world. Since HGS unlocks sophisticated methods for use by anyone with Python skills, we anticipate that it will support subsurface investigations and add value to standard monitoring practice.</p>

Disentangling the groundwater response to Earth and atmospheric tides reveals subsurface processes and properties

2020 ◽  
Author(s):  
Gabriel Rau ◽  
Timothy McMillan ◽  
Mark Cuthbert ◽  
Martin Andersen ◽  
Wendy Timms ◽  
...  
Keyword(s):  
Water Level ◽  
Amplitude Ratio ◽  
Atmospheric Tides ◽  
Frequency Domain Method ◽  
Specific Storage ◽  
Strain Anisotropy ◽  
Geomechanical Properties ◽  
Groundwater Response ◽  
Borehole Water ◽  
Harmonic Components

<p>In situ quantification of subsurface hydro-geomechanical properties is challenging and requires significant effort. Evolving research illustrates that subtle harmonic components in groundwater head measurements caused by Earth and atmospheric tides can be utilised to explore groundwater systems with little effort compared to traditional investigations. One long standing problem has been that, for dominant tidal components, Earth and atmospheric tides occur at the same frequency which prevents the use of the groundwater response to their individual forcing to infer subsurface properties. While Acworth et al. (2016) offered a way forward, their approach has assumptions that limit the applicability. Here, we illustrate an extended method that disentangles the borehole water level response and attributes magnitude and phase to their individual drivers. As a result, we obtain individual changes in harmonic properties of the drivers and their groundwater response (amplitude ratio and phase shift) using borehole water level records from different locations. In conjunction with groundwater flow and poroelastic theory, these properties can be used to infer the state of confinement, quantify specific storage and hydraulic conductivity as well as barometric efficiency of the formation. Further, because the stresses imposed by Earth and atmospheric tides are volumetric and uniaxial, respectively, their individual responses can be used to reveal strain anisotropy. Our new approach is passive, i.e. it only requires the measurements of atmospheric and groundwater pressure records, and can provide further insight into subsurface processes and properties using information hidden in standard pressure records.</p><p> </p><p>Acworth, R. I., Halloran, L. J. S., Rau, G. C., Cuthbert, M. O., and Bernardi, T. L. ( 2016), An objective frequency domain method for quantifying confined aquifer compressible storage using Earth and atmospheric tides, Geophys. Res. Lett., 43, 11,671–11,678, doi:10.1002/2016GL071328.</p>

Estimation of in-situ hydro-geomechanical properties using the groundwater responses to natural cyclical forcing

2021 ◽  
Author(s):  
Timothy McMillan ◽  
Gabriel Rau ◽  
Wendy Timms ◽  
Martin Andersen
Keyword(s):  
Land Surface ◽  
A Priori Estimate ◽  
Regulatory Compliance ◽  
Earth Tides ◽  
Atmospheric Tides ◽  
Specific Storage ◽  
Low Frequencies ◽  
Geomechanical Properties ◽  
Wide Range

<p>Earth and atmospheric tides are prevalent across the land-surface and provide natural forcing to characterise the hydro-geomechanical confined subsurface by using their groundwater response. Since tides are harmonic, their individual influences on the pressure head can be separated into complex components containing level or pressure magnitudes and phases. The approximated planar strain from Earth tides, and the uniaxial loading from atmospheric tides, allow the estimation of a wide range of values based on hydraulic and poroelastic relationships. With recent research advances, tidal analysis can be used to estimate hydro-geomechanical properties including specific storage, hydraulic conductivity, porosity, shear, Young’s and Bulk moduli, Skempton’s and Biot-Willis coefficients and undrained/drained Poisson’s ratios. This approach does not require any assumption on mineral grain compressibility for unconsolidated systems. However, consolidated materials currently require an a priori estimate of grain compressibility. We applied this method to pressure measurements from different geological settings. The estimated hydro-geomechanical properties comply with theoretically expected values except for Poisson’s ratio, which differs from laboratory values due to differing confining pressures, and comparatively low frequencies of the Earth and Atmospheric tide signals. However, these estimated values from in-situ data are likely more realistic of the natural hydrogeological response. We anticipate that, by developing methods that routinely can derive engineering geotechnical values through the monitoring of hydraulic head variations, the collection of groundwater pressures will become a priority for large civic excavations or construction, such as mining, in addition to environmental studies and regulatory compliance.</p>

Fundamental statistical techniques for the analysis of earth tides

1971 ◽  
Vol 61 (1) ◽  
pp. 203-215
Author(s):  
Cheh Pan
Keyword(s):  
Computer Technology ◽  
Earth Tide ◽  
Power Spectra ◽  
Correlation Coefficients ◽  
Earth Tides ◽  
Statistical Techniques ◽  
The Earth ◽  
Tidal Data ◽  
Instrumental Drift ◽  
Phase Differences

abstract Recent advances in instrumentation, digital computer technology and mathematical theory promote the error analysis of Earth-tide data. Various statistical techniques developed and used in other fields are applicable in the study of Earth tides, and the accuracy of the Earth's rigidity constants determined from the tides will be greatly improved with the help of these techniques. The fundamentals of the statistical techniques of autocorrelation, crosscorrelation, convolution, statistical means, bandpass filtering, correlation coefficients, power spectra, coherency and equalization are described, and their principal applications in the Earth-tide analysis summarized. Examples of effective application of these techniques in the elimination of the errors in the tidal data such as those introduced from instrumental drift, phase differences between the observed and predicted tides, etc. are discussed. This work is an attempt to introduce statistical analysis into the Earth-tide study.

scholarly journals Capillary Effects on Groundwater Response to Earth Tides

2019 ◽  
Vol 55 (8) ◽  
pp. 6886-6895 ◽  
Author(s):  
Chi‐Yuen Wang ◽  
Ai‐Yu Zhu ◽  
Xin Liao ◽  
Michael Manga ◽  
Lee‐Ping Wang
Keyword(s):  
Earth Tides ◽  
Capillary Effects ◽  
Groundwater Response

A review of specific storage values from pore pressure response to passive in situ stresses: Implications for sustainable groundwater management

2020 ◽  
Author(s):  
Wendy A Timms ◽  
M Faysal Chowdhury ◽  
Gabriel C Rau
Keyword(s):  
Groundwater Management ◽  
Pore Pressure ◽  
Pressure Response ◽  
Earth Tides ◽  
Low Permeability ◽  
Specific Storage ◽  
Sustainable Groundwater Management ◽  
In Situ Stresses ◽  
Pore Pressure Response

<p>Specific storage (S<sub>s</sub>) values are important for analyzing the quantity of stored groundwater and for predicting drawdown to ensure sustainable pumping. This research compiled S<sub>s</sub> values from multiple available studies based on pore pressure responses to passive stresses, for comparison and discussion with relevant poroelastic theory and groundwater applications. We find that S<sub>s</sub> values from pore pressure responses to passive in situ stresses ranged from 1.3x10<sup>-7</sup> to 3.7x10<sup>-5</sup> m<sup>-1</sup> (geomean 2.0x10<sup>-6</sup> m-1, n=64 from 24 studies). This large S<sub>s</sub> dataset for confined aquifers included both consolidated and unconsolidated strata by extending two recent literature reviews. The dataset included several passive methods: Individual strains from Earth tides and atmospheric loading, their combined effect, and values derived from soil moisture loading due to rainfall events. The range of S<sub>s</sub> values spans approx. 2 orders of magnitude, far less than for hydraulic conductivity, a finding that has important implications for sustainable groundwater management. Both the range of values and maximum S<sub>s</sub> values in this large dataset were significantly smaller than S<sub>s</sub> values commonly applied including laboratory testing of cores, aquifer pump testing and numerical groundwater modelling. </p><p>Results confirm that S<sub>s</sub> is overestimated by assuming incompressible grains, particularly for consolidated rocks. It was also evident that Ss that commonly assumes uniaxial conditions underestimate S<sub>s</sub> that accounts for areal or volumetric conditions.  Further research is required to ensure that S<sub>s</sub> is not underestimated by assuming instantaneous pore pressure response to strains, particularly in low permeability strata. However, in low permeability strata S<sub>s</sub> could also be overestimated if based on total porosity (or moisture content) rather than a smaller free water content, due to water adsorbed by clay minerals. Further evaluation is also required for influences on S<sub>s</sub> from monitoring bore construction (ie. screen and casing or grouting), and S<sub>s</sub> derived from tidal stresses (undrained or constant mass conditions) that could underestimate S<sub>s</sub> applicable to groundwater pumping (drained or changing mass conditions). In summary, poroelastic effects that are often neglected in groundwater studies are clearly important for quantifying water flow and storage in strata with changing hydraulic stress and loading conditions. </p>

scholarly journals Hydrogeologic Property Estimation in Plate Boundary Observatory Boreholes Using Tidal Response Analysis

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Jacob B. Simon ◽  
Patrick M. Fulton ◽  
Lian Xue
Keyword(s):  
Large Scale ◽  
Seismic Waves ◽  
Plate Boundary ◽  
Earth Tides ◽  
Cascadia Subduction Zone ◽  
Response Analysis ◽  
Specific Storage ◽  
Permeability Enhancement ◽  
Control Fluid ◽  
Pressure Changes

Because of the influence pore pressures have on effective stress, understanding hydrogeologic properties that control fluid flow and pressure distribution is important in characterizing earthquake and deformation processes. Here, we utilize borehole pressure changes in response to earth tides to determine hydrogeologic properties and their time variations for 17 boreholes within the NSF Earthscope’s Plate Boundary Observatory (PBO) network along the San Andreas fault and Cascadia subduction zone. Our analysis considers solutions for both confined and unconfined aquiares. Resulting permeability and hydraulic diffusivity values range from 6.4 × 10 − 16 – 8.4 × 10 − 14  m2 and 1 × 10 − 4 – 9 × 10 − 1   m 2 s − 1 , respectively, whereas specific storage values are generally ~ 1 × 10 − 6   m − 1 . The values are fairly consistent through time, reasonable given lithology, and are comparable to other regional studies. For one borehole, values are also comparable to those determined with traditional aquifer test data. In contrast with previous determinations of the high-frequency poroelastic response to seismic waves, no obvious spatial trends in hydrogeologic properties determined from long-wavelength tidal perturbations are observed. Within the recurring time-series estimates, only one borehole exhibits clear permeability enhancement by earthquakes, whereas nearby boreholes with similar lithology and hydrogeologic property values do not. This highlights the variable susceptibility of rocks to permeability enhancement. Together, these results provide quantitative constraints useful for models of large-scale groundwater flow around large fault systems and the potential hydrologic influence on deformation and fault slip behavior.

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