A. Hinnell | University of Arizona (original) (raw)
Papers by A. Hinnell
[1] Infiltration per unit area of the source region from discs, strips and furrows has previously... more [1] Infiltration per unit area of the source region from discs, strips and furrows has previously been shown to be the sum of the one-dimensional infiltration and an edge effect term. Here we apply the same approach to examine infiltration under a constant head from boreholes (both lined and unlined). A critical empirical parameter (g) in the edge effect term is related to the radius of the borehole, soil hydraulic properties, boundary and initial conditions. For lined boreholes, g has a narrow range and for the examples investigated, a constant value of 1.06 introduces less than 5% error compared to using the case-specific g value. For unlined boreholes, g is larger, ranging between 1.02 and 3.16 for the examples investigated, and should be estimated for specific conditions.
SEG Technical Program Expanded Abstracts 2000, 2000
Mapping discontinuous permafrost in the Canadian Sub‐Arctic using a combination of airborne and s... more Mapping discontinuous permafrost in the Canadian Sub‐Arctic using a combination of airborne and surface geophysical surveys. [SEG Technical Program Expanded Abstracts 19, 1351 (2000)]. Richard Kellett, Andrew Hinnell, Jeff Gamey, Greg Hodges.
We studied the response of multi-band quad-polarized synthetic aperture radar to soil moisture at... more We studied the response of multi-band quad-polarized synthetic aperture radar to soil moisture at a Mars analog site, finding significant correlation for surface moisture at L-VV on a smooth surface and no correlation for deeper depth or rougher surface.
The Leading Edge, 2006
... This determination could be made with repeat ring infiltrometer measurements of flux at many ... more ... This determination could be made with repeat ring infiltrometer measurements of flux at many locations within the ... simple virtual experiment has yielded useful insights into the use of surface-based electrical resistivity methods for inferring hydraulic parameters during ponded ...
The search for surface and near-surface liquid water on Mars is a central part of current and pla... more The search for surface and near-surface liquid water on Mars is a central part of current and planned future exploration. We present preliminary results from SAR analog studies at three test sites to remotely measure soil moisture content .
Water Resources Research, 2009
There is increasing interest in the use of multiple measurement types, including indirect (geophy... more There is increasing interest in the use of multiple measurement types, including indirect (geophysical) methods, to constrain hydrologic interpretations. To date, most examples integrating geophysical measurements in hydrology have followed a three-step, uncoupled inverse approach. This approach begins with independent geophysical inversion to infer the spatial and/or temporal distribution of a geophysical property (e.g. electrical conductivity). The geophysical property is
Symposium on the Application of Geophysics to Engineering and Environmental Problems 2011, 2011
Paired measurements of water table elevation and water content profiles were collected within the... more Paired measurements of water table elevation and water content profiles were collected within the combined zone of influence of three pumped wells during pumping and recovery. Water content profiles were measured using zero offset borehole ground penetrating radar (BGPR). This electromagnetic method gives high-resolution (25 cm) rapid (
Heterogeneous hydrologic properties lead to complex pathways for solute transport and spatially n... more Heterogeneous hydrologic properties lead to complex pathways for solute transport and spatially nonuniform distributions of solute mass through time. This nonuniformity presents challenges for characterizing solute mass distributions using conventional point sampling. Furthermore, it is unclear how relatively few point measurements can be combined to give reasonable estimates of the total solute mass. These challenges have led to increased interest in the use of geophysical (especially electrical) methods to characterize solute distributions through space and time. Although individual measurements of electrical resistance are rapid, collecting sufficient data to constrain the estimation of the electrical resistivity structure can be expensive. The objective of this study is to determine whether an optimal set of ERT measurements can be identified for the purpose of estimating the total solute mass in a plume through time. An optimal measurement set produces an estimate of the solute...
There is growing interest in the merging of multiple data types for hydrogeological investigation... more There is growing interest in the merging of multiple data types for hydrogeological investigations. The potential value of diverse data cannot be overstated. But, as this diversity increases it becomes increasingly more difficult to judge the relative value of different data types. There has been some discussion recently about the value of joint and/or coupled inversion of hydrologic and geophysical data. We review and explain these approaches. Then, we demonstrate that the value of geophysical data should be considered for one of two uses: to provide context for development of hydrologic conceptual and numerical models; or to provide data with high spatial and/or temporal resolution to be interpreted in the context of a hydrologic model. We conclude by discussing the nature of different geophysical methods that make them better suited to one or the other (but probably not both) uses.
Water Resources Research, 2009
1] Infiltration per unit area of the source region from discs, strips and furrows has previously ... more 1] Infiltration per unit area of the source region from discs, strips and furrows has previously been shown to be the sum of the one-dimensional infiltration and an edge effect term. Here we apply the same approach to examine infiltration under a constant head from boreholes (both lined and unlined). A critical empirical parameter (g) in the edge effect term is related to the radius of the borehole, soil hydraulic properties, boundary and initial conditions. For lined boreholes, g has a narrow range and for the examples investigated, a constant value of 1.06 introduces less than 5% error compared to using the case-specific g value. For unlined boreholes, g is larger, ranging between 1.02 and 3.16 for the examples investigated, and should be estimated for specific conditions.
Electrical resistivity tomography (ERT) is commonly used in hydrologic investigations. Advances i... more Electrical resistivity tomography (ERT) is commonly used in hydrologic investigations. Advances in joint and coupled hydrogeophysical inversion have enhanced the quantitative use of ERT to construct and condition hydrologic models (i.e. identify hydrologic structure and estimate hydrologic parameters). However the selection of which electrical resistivity data to collect and use is often determined by a combination of data requirements for geophysical analysis, intuition on the part of the hydrogeophysicist and logistical constraints of the laboratory or field site. One of the advantages of coupled hydrogeophysical inversion is the direct link between the hydrologic model and the individual geophysical data used to condition the model. That is, there is no requirement to collect geophysical data suitable for independent geophysical inversion. The geophysical measurements collected can be optimized for estimation of hydrologic model parameters rather than to develop a geophysical mod...
Water Resources Research, 2008
Water Resources Research, 2006
1] Intrusive measurement techniques require placing a sensor within the sample, possibly changing... more 1] Intrusive measurement techniques require placing a sensor within the sample, possibly changing the conditions under which the measurement is collected and thereby affecting the quality of the measurement. In this study we consider time domain reflectometry (TDR), which is an intrusive water content measurement method. TDR rods are impermeable, and thus water is forced to flow around the rods. In an unsaturated medium this changes the water content distribution in the vicinity of the rods, with the water content increased at the tops of the rods and decreased at the bottoms of the rods. TDR has nonuniform spatial sensitivity, with much higher sensitivity immediately adjacent to rods, in the regions that experience the greatest change in water content due to this flow disruption. Furthermore, the spatial sensitivity of TDR depends on the water content distribution within the sample volume. This raises the possibility that flow disruptions caused by TDR rods may affect the TDR-measured water content. In this study we are specifically interested in the effects of flow disruption due to TDR rods. Therefore we consider steady state unit gradient unsaturated flow in a homogeneous medium to eliminate spatial heterogeneity of water content due to soil heterogeneity and transient flow conditions. For common TDR probe designs in the wide range of soils examined, flow disruption gives rise to a water content measurement error that is less than 0.005 cm 3 cm À3 . This is smaller than the reported accuracy of the TDR method of 0.02 cm 3 cm À3 . As a result, we conclude that it is appropriate to ignore flow disruption caused by commonly used TDR probes when assessing sources of TDR measurement error.
Water Resources Research, 2008
Vadose Zone Journal, 2006
We examine in-place recharge as an example of the complex, basinscale hydrologic processes that a... more We examine in-place recharge as an example of the complex, basinscale hydrologic processes that are being represented with simplified numerical models. The rate and distribution of recharge depend on local meteorological conditions and hydrogeologic properties. The
Vadose Zone Journal, 2008
A can provide rapid measurements of the permeability of near-surface sediments (e.g., van Groenew... more A can provide rapid measurements of the permeability of near-surface sediments (e.g., van Groenewoud, 1968;. Based on the demonstrated log-log correlation between air permeability (k a ) and saturated hydraulic conductivity (K sat ) , these measurements can be used to estimate K sat without the need to apply water to the soil. Th e ability to measure this important hydraulic property without the use of more cumbersome, time-consuming direct methods may provide a practical approach to generate more complete data for use in distributed hydrologic models.
Near Surface Geophysics, 2014
A commercially available surface NMR instrument was modified to address the challenges of using e... more A commercially available surface NMR instrument was modified to address the challenges of using earth's field surface NMR to detect and characterize water in the unsaturated (or vadose) zone. The modified instrument incorporates faster switching electronics to achieve an instrument dead time of 2.8 ms, and higher output power electronics to enable a maximum coil voltage of 8000 volts and coil current of 800 amps. The instrument was used to collect and interpret surface NMR data at several active vadose zone investigation sites in the western US. A 6-week surface NMR experiment was conducted at a managed aquifer storage and recovery facility in Arizona, to explore the measurement capabilities and limitations of the instrument, during a managed infiltration event. The resulting time lapse surface NMR data were used to map zones of held water prior to the flood event, image the influx of water through the top 15 metres of the subsurface during and after the event, quantify the spatial and temporal distribution of infiltrating water throughout the event, and characterize the distribution of water in different relative pore sizes throughout the event. Data obtained at pseudo-static vadose zone investigation sites indicate that the surface NMR instrument can detect and image some forms of water held in unconsolidated vadose zone formations, at depths up to 30 metres. Complementary NMR logging data indicate that the surface NMR instrument does not detect all of the water held in these pseudo-static formations, but that the non-invasive surface NMR data may yield valuable information nonetheless.
Near Surface Geophysics, 2011
There is increasing interest in the unique measurement capabilities of nuclear magnetic resonance... more There is increasing interest in the unique measurement capabilities of nuclear magnetic resonance (NMR) for hydrologic applications. In particular, the ability to quantify water content (both bound and free) and to infer the permeability distribution are critical to hydrologists. As the method has gained in acceptance, there has been growing interest in extending its range to near-surface and vadose zone applications and to measurement in finer grained and magnetic soils. All of these applications require improved resolution of early-time signals, which requires shorter measurement dead times. This paper analyses three physical/electrical processes that limit the minimum achievable measurement dead times in surface NMR applications: 1) inherent characteristics of electromechanical and semiconductor switching devices, 2) the effective bandwidth of the receiver and signal processing chain, 3) transient signals associated with induced eddy currents in the ground. We then describe two applications of surface NMR that rely on reduced measurement dead time: detection and characterization of fast decaying NMR signals in silt and clay and the detection of fast decaying NMR signals in magnetic geology. 2010, the 'instrument dead time' was further reduced to 4 ms and
[1] Infiltration per unit area of the source region from discs, strips and furrows has previously... more [1] Infiltration per unit area of the source region from discs, strips and furrows has previously been shown to be the sum of the one-dimensional infiltration and an edge effect term. Here we apply the same approach to examine infiltration under a constant head from boreholes (both lined and unlined). A critical empirical parameter (g) in the edge effect term is related to the radius of the borehole, soil hydraulic properties, boundary and initial conditions. For lined boreholes, g has a narrow range and for the examples investigated, a constant value of 1.06 introduces less than 5% error compared to using the case-specific g value. For unlined boreholes, g is larger, ranging between 1.02 and 3.16 for the examples investigated, and should be estimated for specific conditions.
SEG Technical Program Expanded Abstracts 2000, 2000
Mapping discontinuous permafrost in the Canadian Sub‐Arctic using a combination of airborne and s... more Mapping discontinuous permafrost in the Canadian Sub‐Arctic using a combination of airborne and surface geophysical surveys. [SEG Technical Program Expanded Abstracts 19, 1351 (2000)]. Richard Kellett, Andrew Hinnell, Jeff Gamey, Greg Hodges.
We studied the response of multi-band quad-polarized synthetic aperture radar to soil moisture at... more We studied the response of multi-band quad-polarized synthetic aperture radar to soil moisture at a Mars analog site, finding significant correlation for surface moisture at L-VV on a smooth surface and no correlation for deeper depth or rougher surface.
The Leading Edge, 2006
... This determination could be made with repeat ring infiltrometer measurements of flux at many ... more ... This determination could be made with repeat ring infiltrometer measurements of flux at many locations within the ... simple virtual experiment has yielded useful insights into the use of surface-based electrical resistivity methods for inferring hydraulic parameters during ponded ...
The search for surface and near-surface liquid water on Mars is a central part of current and pla... more The search for surface and near-surface liquid water on Mars is a central part of current and planned future exploration. We present preliminary results from SAR analog studies at three test sites to remotely measure soil moisture content .
Water Resources Research, 2009
There is increasing interest in the use of multiple measurement types, including indirect (geophy... more There is increasing interest in the use of multiple measurement types, including indirect (geophysical) methods, to constrain hydrologic interpretations. To date, most examples integrating geophysical measurements in hydrology have followed a three-step, uncoupled inverse approach. This approach begins with independent geophysical inversion to infer the spatial and/or temporal distribution of a geophysical property (e.g. electrical conductivity). The geophysical property is
Symposium on the Application of Geophysics to Engineering and Environmental Problems 2011, 2011
Paired measurements of water table elevation and water content profiles were collected within the... more Paired measurements of water table elevation and water content profiles were collected within the combined zone of influence of three pumped wells during pumping and recovery. Water content profiles were measured using zero offset borehole ground penetrating radar (BGPR). This electromagnetic method gives high-resolution (25 cm) rapid (
Heterogeneous hydrologic properties lead to complex pathways for solute transport and spatially n... more Heterogeneous hydrologic properties lead to complex pathways for solute transport and spatially nonuniform distributions of solute mass through time. This nonuniformity presents challenges for characterizing solute mass distributions using conventional point sampling. Furthermore, it is unclear how relatively few point measurements can be combined to give reasonable estimates of the total solute mass. These challenges have led to increased interest in the use of geophysical (especially electrical) methods to characterize solute distributions through space and time. Although individual measurements of electrical resistance are rapid, collecting sufficient data to constrain the estimation of the electrical resistivity structure can be expensive. The objective of this study is to determine whether an optimal set of ERT measurements can be identified for the purpose of estimating the total solute mass in a plume through time. An optimal measurement set produces an estimate of the solute...
There is growing interest in the merging of multiple data types for hydrogeological investigation... more There is growing interest in the merging of multiple data types for hydrogeological investigations. The potential value of diverse data cannot be overstated. But, as this diversity increases it becomes increasingly more difficult to judge the relative value of different data types. There has been some discussion recently about the value of joint and/or coupled inversion of hydrologic and geophysical data. We review and explain these approaches. Then, we demonstrate that the value of geophysical data should be considered for one of two uses: to provide context for development of hydrologic conceptual and numerical models; or to provide data with high spatial and/or temporal resolution to be interpreted in the context of a hydrologic model. We conclude by discussing the nature of different geophysical methods that make them better suited to one or the other (but probably not both) uses.
Water Resources Research, 2009
1] Infiltration per unit area of the source region from discs, strips and furrows has previously ... more 1] Infiltration per unit area of the source region from discs, strips and furrows has previously been shown to be the sum of the one-dimensional infiltration and an edge effect term. Here we apply the same approach to examine infiltration under a constant head from boreholes (both lined and unlined). A critical empirical parameter (g) in the edge effect term is related to the radius of the borehole, soil hydraulic properties, boundary and initial conditions. For lined boreholes, g has a narrow range and for the examples investigated, a constant value of 1.06 introduces less than 5% error compared to using the case-specific g value. For unlined boreholes, g is larger, ranging between 1.02 and 3.16 for the examples investigated, and should be estimated for specific conditions.
Electrical resistivity tomography (ERT) is commonly used in hydrologic investigations. Advances i... more Electrical resistivity tomography (ERT) is commonly used in hydrologic investigations. Advances in joint and coupled hydrogeophysical inversion have enhanced the quantitative use of ERT to construct and condition hydrologic models (i.e. identify hydrologic structure and estimate hydrologic parameters). However the selection of which electrical resistivity data to collect and use is often determined by a combination of data requirements for geophysical analysis, intuition on the part of the hydrogeophysicist and logistical constraints of the laboratory or field site. One of the advantages of coupled hydrogeophysical inversion is the direct link between the hydrologic model and the individual geophysical data used to condition the model. That is, there is no requirement to collect geophysical data suitable for independent geophysical inversion. The geophysical measurements collected can be optimized for estimation of hydrologic model parameters rather than to develop a geophysical mod...
Water Resources Research, 2008
Water Resources Research, 2006
1] Intrusive measurement techniques require placing a sensor within the sample, possibly changing... more 1] Intrusive measurement techniques require placing a sensor within the sample, possibly changing the conditions under which the measurement is collected and thereby affecting the quality of the measurement. In this study we consider time domain reflectometry (TDR), which is an intrusive water content measurement method. TDR rods are impermeable, and thus water is forced to flow around the rods. In an unsaturated medium this changes the water content distribution in the vicinity of the rods, with the water content increased at the tops of the rods and decreased at the bottoms of the rods. TDR has nonuniform spatial sensitivity, with much higher sensitivity immediately adjacent to rods, in the regions that experience the greatest change in water content due to this flow disruption. Furthermore, the spatial sensitivity of TDR depends on the water content distribution within the sample volume. This raises the possibility that flow disruptions caused by TDR rods may affect the TDR-measured water content. In this study we are specifically interested in the effects of flow disruption due to TDR rods. Therefore we consider steady state unit gradient unsaturated flow in a homogeneous medium to eliminate spatial heterogeneity of water content due to soil heterogeneity and transient flow conditions. For common TDR probe designs in the wide range of soils examined, flow disruption gives rise to a water content measurement error that is less than 0.005 cm 3 cm À3 . This is smaller than the reported accuracy of the TDR method of 0.02 cm 3 cm À3 . As a result, we conclude that it is appropriate to ignore flow disruption caused by commonly used TDR probes when assessing sources of TDR measurement error.
Water Resources Research, 2008
Vadose Zone Journal, 2006
We examine in-place recharge as an example of the complex, basinscale hydrologic processes that a... more We examine in-place recharge as an example of the complex, basinscale hydrologic processes that are being represented with simplified numerical models. The rate and distribution of recharge depend on local meteorological conditions and hydrogeologic properties. The
Vadose Zone Journal, 2008
A can provide rapid measurements of the permeability of near-surface sediments (e.g., van Groenew... more A can provide rapid measurements of the permeability of near-surface sediments (e.g., van Groenewoud, 1968;. Based on the demonstrated log-log correlation between air permeability (k a ) and saturated hydraulic conductivity (K sat ) , these measurements can be used to estimate K sat without the need to apply water to the soil. Th e ability to measure this important hydraulic property without the use of more cumbersome, time-consuming direct methods may provide a practical approach to generate more complete data for use in distributed hydrologic models.
Near Surface Geophysics, 2014
A commercially available surface NMR instrument was modified to address the challenges of using e... more A commercially available surface NMR instrument was modified to address the challenges of using earth's field surface NMR to detect and characterize water in the unsaturated (or vadose) zone. The modified instrument incorporates faster switching electronics to achieve an instrument dead time of 2.8 ms, and higher output power electronics to enable a maximum coil voltage of 8000 volts and coil current of 800 amps. The instrument was used to collect and interpret surface NMR data at several active vadose zone investigation sites in the western US. A 6-week surface NMR experiment was conducted at a managed aquifer storage and recovery facility in Arizona, to explore the measurement capabilities and limitations of the instrument, during a managed infiltration event. The resulting time lapse surface NMR data were used to map zones of held water prior to the flood event, image the influx of water through the top 15 metres of the subsurface during and after the event, quantify the spatial and temporal distribution of infiltrating water throughout the event, and characterize the distribution of water in different relative pore sizes throughout the event. Data obtained at pseudo-static vadose zone investigation sites indicate that the surface NMR instrument can detect and image some forms of water held in unconsolidated vadose zone formations, at depths up to 30 metres. Complementary NMR logging data indicate that the surface NMR instrument does not detect all of the water held in these pseudo-static formations, but that the non-invasive surface NMR data may yield valuable information nonetheless.
Near Surface Geophysics, 2011
There is increasing interest in the unique measurement capabilities of nuclear magnetic resonance... more There is increasing interest in the unique measurement capabilities of nuclear magnetic resonance (NMR) for hydrologic applications. In particular, the ability to quantify water content (both bound and free) and to infer the permeability distribution are critical to hydrologists. As the method has gained in acceptance, there has been growing interest in extending its range to near-surface and vadose zone applications and to measurement in finer grained and magnetic soils. All of these applications require improved resolution of early-time signals, which requires shorter measurement dead times. This paper analyses three physical/electrical processes that limit the minimum achievable measurement dead times in surface NMR applications: 1) inherent characteristics of electromechanical and semiconductor switching devices, 2) the effective bandwidth of the receiver and signal processing chain, 3) transient signals associated with induced eddy currents in the ground. We then describe two applications of surface NMR that rely on reduced measurement dead time: detection and characterization of fast decaying NMR signals in silt and clay and the detection of fast decaying NMR signals in magnetic geology. 2010, the 'instrument dead time' was further reduced to 4 ms and