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>

scholarly journals Special Issue on Remote Sensing of Snow and Its Applications

Geosciences ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 277 ◽  
Author(s):  
Ali Nadir Arslan ◽  
Zuhal Akyürek
Keyword(s):  
Remote Sensing ◽  
Snow Cover ◽  
Land Surface ◽  
Climate Models ◽  
Weather Forecasting ◽  
Special Issue ◽  
Carbon Cycles ◽  
Wide Range ◽  
Remote Sensing Techniques

Snow cover is an essential climate variable directly affecting the Earth’s energy balance. Snow cover has a number of important physical properties that exert an influence on global and regional energy, water, and carbon cycles. Remote sensing provides a good understanding of snow cover and enable snow cover information to be assimilated into hydrological, land surface, meteorological, and climate models for predicting snowmelt runoff, snow water resources, and to warn about snow-related natural hazards. The main objectives of this Special Issue, “Remote Sensing of Snow and Its Applications” in Geosciences are to present a wide range of topics such as (1) remote sensing techniques and methods for snow, (2) modeling, retrieval algorithms, and in-situ measurements of snow parameters, (3) multi-source and multi-sensor remote sensing of snow, (4) remote sensing and model integrated approaches of snow, and (5) applications where remotely sensed snow information is used for weather forecasting, flooding, avalanche, water management, traffic, health and sport, agriculture and forestry, climate scenarios, etc. It is very important to understand (a) differences and similarities, (b) representativeness and applicability, (c) accuracy and sources of error in measuring of snow both in-situ and remote sensing and assimilating snow into hydrological, land surface, meteorological, and climate models. This Special Issue contains nine articles and covers some of the topics we listed above.

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>

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>

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 Combination satellite and in-situ data for the determination of evapotranspiration over heterogeneous landscape of the Tibetan Plateau

2013 ◽  
Vol 13 (3) ◽  
pp. 8435-8453
Author(s):  
Y. Ma ◽  
Z. Zhu ◽  
L. Zhong ◽  
B. Wang ◽  
C. Han ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
The Tibetan Plateau ◽  
Modis Data ◽  
In Situ Data ◽  
Heterogeneous Landscape ◽  
Plateau Area ◽  
Wide Range ◽  
Avhrr Data

Abstract. In this study, a new parameterization method based on MODIS (Moderate Resolution Imaging Spectroradiometer) data, AVHRR (Advanced Very High-Resolution Radiometer) data and in-situ data is constructed and tested for deriving the regional evaporative fraction (EF) over heterogeneous landscape. As a case study, the methodology was applied to the Tibetan Plateau area. Eight images of MODIS data (17 January 2003, 14 April 2003, 23 July 2003 and 16 October 2003; 30 January 2007, 15 April 2007, 1 August 2007 and 25 October 2007) and four images of AVHRR data (17 January 2003, 14 April 2003, 23 July 2003 and 16 October 2003) were used in this study for the comparison among winter, spring, summer and autumn and the annual variation analysis. The derived results were also validated by using the "ground truth" measured in the stations of the Tibetan Observation and Research Platform (TORP) and the CAMP/Tibet (CEOP (Coordinated Enhanced Observing Period) Asia-Australia Monsoon Project (CAMP) on the Tibetan Plateau). The results show that the derived EF in four different seasons over the Tibetan Plateau area is in good accordance with the land surface status. The EF show a wide range due to the strong contrast of surface features over the Tibetan Plateau. Also, the estimated EF is in good agreement with the ground measurements, and their absolute percent difference (APD) is less than 10% in the validation sites. The results from AVHRR were also in agreement with MODIS, with the latter usually displaying a higher level of accuracy. It is therefore concluded that the proposed methodology is successful for the retrieval of EF using the MODIS data, AVHRR data and in-situ data over the Tibetan Plateau area, and the MODIS data is the better one and it should be used widely for the evapotranspiration (ET) research over this region.

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.

scholarly journals Determination of Mining-Induced Changes in Hydrogeological Parameters of Overburden Aquifer in a Coalfield, Northwest China: Approaches Using the Water Level Response to Earth Tides

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Qingyu Xu ◽  
Guangcai Wang ◽  
Xiangyang Liang ◽  
Shen Qu ◽  
Zheming Shi ◽  
...  
Keyword(s):  
Water Level ◽  
Northwest China ◽  
Earth Tides ◽  
Well Water ◽  
Coal Face ◽  
Specific Storage ◽  
Hydrogeological Parameters ◽  
Well Water Level

The determination of changes in hydrogeological properties (e.g., permeability and specific storage) of aquifers disturbed by mining activity is significant to groundwater resource and ecological environment protection in coal mine areas. However, such parameters are difficult to continuously measure in situ using conventional hydrogeological methods, and their temporal changes associated with coal mining are not well understood. The response of well water level to Earth tides provides a unique probe to determine the in situ hydrogeological parameters and their variations. In this study, the tidal responses of well water level were employed to characterize the changes in hydrogeological parameters of the overburden aquifer induced by longwall mining in a coalfield, northwest China. Based on the long-term hourly recorded water level data, two analytical models were used to determine the temporal changes of permeability and specific storage of the overburden aquifer. The results showed that the hydrogeological parameters changed with the longwall coal face advance. When the longwall coal face approached the wells, the aquifer permeability increased several to dozens of times, and the response distance ranged from 80 m to 300 m. The specific storage decreased before the coal face reached wells and recovered after the coal face passed. The results of this study indicate that the hydrogeological parameter changes induced by coal mining are related to the location of the well relative to the coal face and the stress distribution in the overburden aquifer. This study revealed the changes in permeability and specific storage associated with the mining disturbance which could have great significance for quantitative assessment of the impact of mining on overburden aquifer.

scholarly journals In-situ estimation of subsurface hydro-geomechanical properties using the groundwater response to Earth and atmospheric tides

2021 ◽  
Author(s):  
Timothy C. McMillan ◽  
Martin S. Andersen ◽  
Wendy A. Timms ◽  
Gabriel C. Rau
Keyword(s):  
Water Levels ◽  
Atmospheric Tides ◽  
New Approach ◽  
Geomechanical Properties ◽  
Groundwater Response ◽  
In Situ Conditions ◽  
The Impact ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

Abstract. Subsurface hydro-geomechanical properties crucially underpin the management of Earth's resources, yet they are predominantly measured on core-samples in the laboratory while little is known about the representativeness of in-situ conditions. The impact of Earth and atmospheric tides on borehole water levels are ubiquitous and can be used to characterise the subsurface. We illustrate that disentangling the groundwater response to Earth and atmospheric tidal forces in conjunction with hydraulic and linear poroelastic theories leads to a complete determination of the whole hydro-geomechanical parameter space for unconsolidated systems. Further, the characterisation of consolidated systems is possible when using literature estimates of the grain compressibility. While previous field investigations have assumed a Poisson's ratio from literature values, our new approach allows for its estimation under in-situ field conditions. We apply this method to water level and barometric pressure records from four field sites with contrasting hydrogeology. Estimated hydro-geomechanical properties (e.g. specific storage, hydraulic conductivity, porosity, shear-, Young's- and bulk- moduli, Skempton's and Biot-Willis coefficients and undrained/drained Poisson's ratios) are comparable to values reported in the literature, except for consistently negative drained Poisson's ratios which are surprising. Our results reveal an anisotropic response to strain, which is expected for a heterogeneous (layered) lithological profile. Closer analysis reveals that negative Poisson's ratios can be explained by differing in-situ conditions to those from typical laboratory core tests and the small strains generated by Earth and atmospheric tides. Our new approach can be used to passively, and therefore cost-effectively, estimate subsurface hydro-geomechanical properties representative of in-situ conditions. Our method can be used to improve our understanding of the relationship between geological heterogeneity and geomechanical behaviour.

scholarly journals Development of observation-based global multilayer soil moisture products for 1970 to 2016

2021 ◽  
Vol 13 (9) ◽  
pp. 4385-4405
Author(s):  
Yaoping Wang ◽  
Jiafu Mao ◽  
Mingzhou Jin ◽  
Forrest M. Hoffman ◽  
Xiaoying Shi ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Root Mean Square ◽  
Land Surface ◽  
Soil Layer ◽  
Added Value ◽  
Surface Model ◽  
Mean Square ◽  
Wide Range ◽  
Mean Square Errors

Abstract. Soil moisture (SM) datasets are critical to understanding the global water, energy, and biogeochemical cycles and benefit extensive societal applications. However, individual sources of SM data (e.g., in situ and satellite observations, reanalysis, offline land surface model simulations, Earth system model – ESM – simulations) have source-specific limitations and biases related to the spatiotemporal continuity, resolutions, and modeling and retrieval assumptions. Here, we developed seven global, gap-free, long-term (1970–2016), multilayer (0–10, 10–30, 30–50, and 50–100 cm) SM products at monthly 0.5∘ resolution (available at https://doi.org/10.6084/m9.figshare.13661312.v1; Wang and Mao, 2021) by synthesizing a wide range of SM datasets using three statistical methods (unweighted averaging, optimal linear combination, and emergent constraint). The merged products outperformed their source datasets when evaluated with in situ observations (mean bias from −0.044 to 0.033 m3 m−3, root mean square errors from 0.076 to 0.104 m3 m−3, Pearson correlations from 0.35 to 0.67) and multiple gridded datasets that did not enter merging because of insufficient spatial, temporal, or soil layer coverage. Three of the new SM products, which were produced by applying any of the three merging methods to the source datasets excluding the ESMs, had lower bias and root mean square errors and higher correlations than the ESM-dependent merged products. The ESM-independent products also showed a better ability to capture historical large-scale drought events than the ESM-dependent products. The merged products generally showed reasonable temporal homogeneity and physically plausible global sensitivities to observed meteorological factors, except that the ESM-dependent products underestimated the low-frequency temporal variability in SM and overestimated the high-frequency variability for the 50–100 cm depth. Based on these evaluation results, the three ESM-independent products were finally recommended for future applications because of their better performances than the ESM-dependent ones. Despite uncertainties in the raw SM datasets and fusion methods, these hybrid products create added value over existing SM datasets because of the performance improvement and harmonized spatial, temporal, and vertical coverages, and they provide a new foundation for scientific investigation and resource management.

scholarly journals VALIDATION AND UPSCALING OF SOIL MOISTURE SATELLITE PRODUCTS IN ROMANIA

2016 ◽  
Vol XLI-B2 ◽  
pp. 313-317 ◽  
Author(s):  
I. Sandric ◽  
A. Diamandi ◽  
N. Oana ◽  
D. Saizu ◽  
C. Vasile ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Surface Temperature ◽  
Land Surface Temperature ◽  
Soil Texture ◽  
Soil Type ◽  
Land Surface ◽  
Vegetation Type ◽  
In Situ Measurements ◽  
Wide Range

The study presents the validation of SMOS soil moisture satellite products for Romania. The validation was performed with in-situ measurements spatially distributed over the country and with in-situ measurements concentrated in on small area. For country level a number of 20 stations from the national meteorological observations network in Romania were selected. These stations have in-situ measurements for soil moisture in the first 5 cm of the soil surface. The stations are more or less distributed in one pixel of SMOS, but it has the advantage that covers almost all the country with a wide range of environmental conditions. Additionally 10 mobile soil moisture measurements stations were acquired and installed. These are spatially concentrated in one SMOS pixel in order to have a more detailed validation against the soil type, soil texture, land surface temperature and vegetation type inside one pixel. The results were compared and analyzed for each day, week, season, soil type, and soil texture and vegetation type. Minimum, maximum, mean and standard deviation were extracted and analyzed for each validation criteria and a hierarchy of those were performed. An upscaling method based on the relations between soil moisture, land surface temperature and vegetation indices was tested and implemented. The study was financed by the Romanian Space Agency within the framework of ASSIMO project <a href="http://assimo.meteoromania.ro"target="_blank">http://assimo.meteoromania.ro</a>.

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