Mapping the Volumetric Soil Water Content of a California Vineyard Using High-Frequency GPR Ground Wave Data

An attempt was made to establish the utility of ground-penetrating radar (GPR) as a quick and noninvasive field tool for shallow soil water content estimates as a function of space and time. Initially, detailed studies of collocated data, with electromagnetic velocity estimates from GPR data compared to gravimetric measurements of water content and to soil testure were carried out. Using the procedures developed during the detailed studies, full grids of GPR data were collected over the entire site several times. Data obtained indicate that incorporation of multiple frequency GPR grids can provide high-resolution estimates of soil water content variations as a function of depth as well as space and time

Field-Scale Estimation of Volumetric Water Content Using Ground-Penetrating Radar Ground Wave Techniques

Ground-penetrating radar (GPR) ground wave techniques were applied to estimate soil water content in the uppermost ∼10 cm of a 3 acre California vineyard several times over 1 year. We collected densely spaced GPR travel time measurements using 900 and 450 MHz antennas and analyzed these data to estimate water content. The spatial distribution of water content across the vineyard did not change significantly with time, although the absolute water content values varied seasonally and with irrigation. The GPR estimates of water content were compared to gravimetric water content, time domain reflectometry, and soil texture measurements. The comparisons of GPR-derived estimates of water content to gravimetric water content measurements showed that the GPR estimates had a root mean square error of volumetric water content of the order of 0.01. The results from this study indicate that GPR ground waves can be used to provide noninvasive, spatially dense estimates of shallow water content over large areas and in a rapid manner

GPR Monitoring of Volumetric Water Content in Soils Applied to Highway Construction and Maintenance

An overview is given on two experiments, a controlled pit study and a transportation application in subasphalt soils. Both experiments show that common-offset ground-penetrating radar (GPR) reflection data can be used to estimate θv to a high degree of accuracy. The methodology developed in these two experiments provides a technique for obtaining quick, noninvasive, accurate, and high-resolution estimates of θv

Characterization of Soil Water Content Variability and Soil Texture Using GPR Groundwave Techniques

Accurate characterization of near-surface soil water content is vital for guiding agricultural management decisions and for reducing the potential negative environmental impacts of agriculture. Characterizing the near-surface soil water content can be difficult, as this parameter is often both spatially and temporally variable, and obtaining sufficient measurements to describe the heterogeneity can be prohibitively expensive. Understanding the spatial correlation of near-surface soil water content can help optimize data acquisition and improve understanding of the processes controlling soil water content at the field scale. In this study, ground penetrating radar (GPR) methods were used to characterize the spatial correlation of water content in a three acre field as a function of sampling depth, season, vegetation, and soil texture. GPR data were acquired with 450 MHz and 900 MHz antennas, and measurements of the GPR groundwave were used to estimate soil water content at four different times. Additional water content estimates were obtained using time domain reflectometry measurements, and soil texture measurements were also acquired. Variograms were calculated for each set of measurements, and comparison of these variograms showed that the horizontal spatial correlation was greater for deeper water content measurements than for shallower measurements. Precipitation and irrigation were both shown to increase the spatial variability of water content, while shallowly-rooted vegetation decreased the variability. Comparison of the variograms of water content and soil texture showed that soil texture generally had greater small-scale spatial correlation than water content, and that the variability of water content in deeper soil layers was more closely correlated to soil texture than were shallower water content measurements. Lastly, cross-variograms of soil texture and water content were calculated, and co-kriging of water content estimates and soil texture measurements showed that geophysically-derived estimates of soil water content could be used to improve spatial estimation of soil texture

Multi-Scale Mass Transfer Processes Controlling Natural Attenuation and Engineered Remediation: An IFRC Focused on Hanford?s 300 Area Uranium Plume January 2010 to January 2011

The Integrated Field Research Challenge (IFRC) at the Hanford Site 300 Area uranium (U) plume addresses multi-scale mass transfer processes in a complex subsurface biogeochemical setting where groundwater and riverwater interact. A series of forefront science questions on reactive mass transfer motivates research. These questions relate to the effect of spatial heterogeneities; the importance of scale; coupled interactions between biogeochemical, hydrologic, and mass transfer processes; and measurements and approaches needed to characterize and model a mass-transfer dominated biogeochemical system. The project was initiated in February 2007, with CY 2007, CY 2008, CY 2009, and CY 2010 progress summarized in preceding reports. A project peer review was held in March 2010, and the IFRC project acted upon all suggestions and recommendations made in consequence by reviewers and SBR/DOE. These responses have included the development of 'Modeling' and 'Well-Field Mitigation' plans that are now posted on the Hanford IFRC web-site, and modifications to the IFRC well-field completed in CY 2011. The site has 35 instrumented wells, and an extensive monitoring system. It includes a deep borehole for microbiologic and biogeochemical research that sampled the entire thickness of the unconfined 300 A aquifer. Significant, impactful progress has been made in CY 2011 including: (i) well modifications to eliminate well-bore flows, (ii) hydrologic testing of the modified well-field and upper aquifer, (iii) geophysical monitoring of winter precipitation infiltration through the U-contaminated vadose zone and spring river water intrusion to the IFRC, (iv) injection experimentation to probe the lower vadose zone and to evaluate the transport behavior of high U concentrations, (v) extended passive monitoring during the period of water table rise and fall, and (vi) collaborative down-hole experimentation with the PNNL SFA on the biogeochemistry of the 300 A Hanford-Ringold contact and the underlying redox transition zone. The modified well-field has functioned superbly without any evidence for well-bore flows. Beyond these experimental efforts, our site-wide reactive transport models (PFLOTRAN and eSTOMP) have been updated to include site geostatistical models of both hydrologic properties and adsorbed U distribution; and new hydrologic characterization measurements of the upper aquifer. These increasingly robust models are being used to simulate past and recent U desorption-adsorption experiments performed under different hydrologic conditions, and heuristic modeling to understand the complex functioning of the smear zone. We continued efforts to assimilate geophysical logging and 3D ERT characterization data into our site wide geophysical model, with significant and positive progress in 2011 that will enable publication in 2012. Our increasingly comprehensive field experimental results and robust reactive transport simulators, along with the field and laboratory characterization, are leading to a new conceptual model of U(VI) flow and transport in the IFRC footprint and the 300 Area in general, and insights on the microbiological community and associated biogeochemical processes influencing N, S, C, Mn, and Fe. Collectively these findings and higher scale models are providing a unique and unparalleled system-scale understanding of the biogeochemical function of the groundwater-river interaction zone

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Contaminant Transport in Groundwater for Environmental Performance Assessment

A methodology for simulating 3-D flow and reactive solute transport through statistically anisotropic heterogeneous porous media was developed and demonstrated. First, a method for generating 3-D flow fields in statistically anisotropic heterogeneous porous media was presented. Sample flow fields were generated and analyzed to demonstrate the method and examine the characteristics of 3-D subsurface flow. This stochastic technique was then coupled with a mobile-immobile domain model for simulating the sorption processes. Model results for the spatial moments of the solute plume were shown to capture the major trends observed in the field-scale experiment performed at Borden. These simulations were based on basic site information and independent laboratory data was used to determine the sorption parameters. In a second application of the model, a series of simulations was completed to investigate the coupled effects of heterogeneities of subsurface hydraulic properties and nonequilibrium processes on reactive solute concentrations undergoing transport in three-dimensional natural porous formations

Geophysical Imaging For Contaminated Site Characterization

The analysis and management of groundwater flow problems often involve the prediction of fluid flow and/or contaminant migration patterns. These phenomena, however, are strongly influenced by the heterogeneity of the hydrogeological properties of the soil. The purpose of this project is to derive joint geophysical-hydrogeological procedures for the characterization of subsurface flow parameters. The first part of this study presents a formal stochastic approach for the integration of surface seismic data and well data into the identification of the spatial arrangement- location, geometry, and interconnectedness of lithofacies. Towards this goal, the lithology of the subsurface is represented through a random indicator function whose spatial structure is identified from seismic reflection data and well logs. Seismic interval velocities and measures of their uncertainties are computed from normal moveout corrections to the seismic reflection data. Calibration curves constructed from the well logs transform these velocity estimates into a lithology indicator prior probability field. From the well data and the prior probability field, the indicator covariance function and its associated confidence limits are computed. Neighboring lithology logs and the indicator covariance function are then combined to update the indicator probability field. To illustrate the applicability of the proposed characterization procedure, a semi-synthetic case study- based on the Fremont study area near the city of Fremont, California- is performed.In the second part of this study, a Bayesian method is developed to estimate the spatial distribution of the permeability. In addition to sparsely sampled permeability and pressure data, the proposed approach incorporates densely sampled seismic velocity data along with semi-empirical relationships between seismic velocity, permeability and pressure. A hydrological inversion is first performed, based solely on the permeability and pressure data. In light of the available seismic data, the velocity-permeability-pressure relationships are then used to update, in a Bayesian sense, the image of the permeability field. To demonstrate the usefulness of this approach, synthetic case studies are performed. For further validation, the proposed methodology is applied to real data collected at Kesterson Reservoir, California. These studies demonstrate that by joining seismic data and hydrological data into a common inverse procedure, improved permeability images can be reproduced

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Transport in heterogeneous sediments with multimodal conductivity and hierarchical organization across scale

Review of Permeability in Buried-Valley Aquifers: Centimeter to Kilometer Scales

Aquifer systems are considered in which measurements of logpermeability (Y) at a 1E-2 m support scale are unimodally disfaibuted as taken within the 1E0 to 1E1 m scale of individual sand and gravel (sg) lithofacies, are weakly multimodal at the 1E1 to 1E2 m scale of assemblages of these facies, and are strongly multimodal at the 1E3 m scale of complexes of sg facies assemblages juxtaposed with mud and diamicton (md) facies assemblages. Contaminant plumes resulting from decades-old disposal have grown to the 1E3 m scale with a high probability of sampling both facies assemblages in the complex. The relevant aspects of the complicated residence time distribution (varying orders of magnitude between the time of travel in preferential pathways through sg facies assemblages and the longer time of travel if in part through md facies assemblages) of mass at this scale is explained by the heterogeneity in the pattern of facies assemblages in the complex; in-facies permeability structure is not important. However, recent spills and tracer tests create smaller plumes at the 1E1 to 1E2 m scale. Here the spatial structure of in-facies permeability and the spatial structure of facies within the sg assemblage is relevant. A hierarchical random space function model gives the global spatial structure of Y as a linear function of the mean, variance, the two point auto and cross-covariance of Yi for each i facies, as weighted by the auto and cross-transition probabilities representing the proportions, the modality, mean and variance in facies lengths, and the juxtapositioning pattern of the facies. This is illustrated with data from an outcrop analogue study