Rectangular Schlumberger arrays can be used for 2-dimensional lateral profiling of apparent resistivity at a unique current electrode separation, hence single depth of penetration. Numerous apparent resistivity measurements are collected moving the potential electrodes (fixed MN spacing) within a rectangle of defined dimensions. The method provides a fast, cost-effective means for the collection of dense resistivity data to provide high-resolution information on subsurface hydeogeologic conditions. Several rectangular Schlumberger resistivity arrays were employed at Los Alamos National Laboratory (IANL) from 1989 through 1995 in an area adjacent to and downhill from an outfall pipe, septic tank, septic drainfield, and sump. Six rectangular arrays with 2 AB spacings were used to delineate lateral low resistivity anomalies that may be related to fractures that contain clay and/or vadose zone water. Duplicate arrays collected over a three year time period exhibited very good data repeatability.The properties of tritium make it an excellent groundwater tracer. Because triiium was present in discharged water from all of the anthropogenic sources in the vicinity it was used for this purpose. One major low resistivity anomaly correlates with relatively high tritium concentrations in the tuff. This was determined from borehole samples collected within and outside of the anomalous zone. The anomaly is interpreted to be due to fractures that contain clay from the soil profile. The clay was deposited in the fractures by aeolian processes and by surface water infiltration. The fractures likely served as a shallow vadose zone groundwater pathway.
Yellowstone National Park hosts over 10,000 thermal features (e.g. geysers, fumaroles, mud pots, and hot springs), yet little is known about the circulation depth of meteoric water feeding these features, the pathways that guide deep, hot fluids to the surface, or the separation depth of the steam that sources vapor-dominated systems. Previous near-surface geophysical studies have been effective in imaging shallow hydrothermal pathways in some areas of the park, but these methods are difficult to conduct over the large areas needed to characterize entire hydrothermal systems. Transient electromagnetic (TEM) soundings and 2D direct current (DC) resistivity profiles show that hydrothermal fluids at active sites have a higher electrical conductivity than the surrounding hydrothermally inactive areas. For that reason, airborne TEM should be an effective method to characterize large areas and identify hydrothermally active and inactive zones using electrical conductivity.Here we present preliminary results from an airborne transient electromagnetic (TEM) and magnetic survey acquired jointly by the U.S. Geological Survey (USGS) and the University of Wyoming (UW) in November 2016. At the time of this writing, the survey is planned to cover 2600 line-km of data at two scales: regional surveys with lines spaced 450 apart and two smaller, high-resolution surveys with line spacing of 150 m. The regional survey will cover northern Yellowstone Lake, the Norris-Mammoth corridor, and the Upper Geyser basin. The high-resolution surveys focus on the Upper Geyser Basin (including Old Faithful) and the Norris Geyser Basin. Data will be acquired with the SkyTEM 312, with a magnetic moment of 0.5 M A-m2. We will present preliminary inversions using the Aarhus Workbench software, with particular focus on the depths of vapor phase separation and the connectivity of pathways of meteoric water recharge. AbstractThe source of adequate groundwater resources to support community and industry (pastoral and mining) in the arid APY Lands of northern South Australia has been the subject of considerable concern since the establishment of cattle stations and community centres in the early 1900's. Although small, locally confined fractured rock aquifer systems have been defined, finding large sustainable sedimentary alluvial aquifers has been problematic despite numerous drilling campaigns over 60+ years. Challenges to their identification include a complex, apparently compartmentalised sedimentary (regolith) cover sequence, highly varying alluvial aquifer thicknesses, and the paucity of spatial information. The low sporadic rainfall/recharge and high average annual evaporation results in a highly variable groundwater quality adding to the complexity of resource determination.The role of geophysical data in addressing these shortcomings has been the subject of more recent investigation. Local scale exploration airborne EM data sets have highlighted the spatial complexity of the alluvial aquifers in the region. Airborne magnetic data, also acquired...
Yucca Mountain, Nevada has been proposed as the site of the high-level nuclear waste repository for the United States. The repository concept uses the philosophy of multiple barriers, both engineered and natural, each of which impedes the movement of radionuclides into the accessible environment. The proposed repository would be in the unsaturated zone in Tertiary tuffaceous rocks. The principal transporting mechanism for radionuclides is moving ground water. Underlying the repository is an extensive Lower Carbonate Aquifer known to be highly permeable. Inyo County, as an affected unit of local government under the Nuclear Waste Policy Act, as amended, is concerned with the connections between the Lower Carbonate Aquifer underlying Yucca Mountain and the carbonate sources of waters in Inyo County, especially the Death Valley region. A primary concern of Inyo County is the potential connection between the carbonate aquifer beneath Yucca Mountain and the system of springs that discharge along the foot of the mountain ranges along the eastern wall of Death Valley.
Los Alamos National Laboratory, an affirmative actiodequal opportunity empldyer, is operated by the University of California for the U.S. Department of Energy under mntract W-7405-ENG-36. By acceptance of this arti @!. the publisher recognizes that the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this mntribution$f requests that the publisher identify this article as work perform nt purposes. The Los Alamos National Laboratory nt of Energy.
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