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Ennetbaden, Switzerland

Jordan D.L.,INTERA Incorporated | Barroll P.,New Mexico Office of the State Engineer
Journal of the American Water Resources Association | Year: 2013

A time series of estimates of irrigated area was developed for the Lower Rio Grande valley (LRG) in New Mexico from the 1970s to present day. The objective of the project was to develop an independent, accurate, and scientifically justifiable evaluation of irrigated area in the region for the period spanning from the mid-1970s to the present. These area estimates were used in support of groundwater modeling of the LRG region, as well as for other analyses. This study used a remote-sensing-based methodology to evaluate overall irrigated area within the LRG. We applied a methodology that involved the normalization of vegetation indices derived from satellite imagery to get a more accurate estimation of irrigated area across multiple time periods and multiple Landsat platforms. The normalization allows more accurate evaluation of vegetation index data that span several decades. An accuracy assessment of the methodology and results from this study was performed using field-collected crop data from the 2008 growing season. The comparisons with field data indicate that the accuracy of the remote-sensing-based estimates of historical irrigated area is very good, with rates of false positives (areas identified as irrigated that are not truly irrigated) of only about 4%, and rates of false negatives (areas identified as not irrigated that are truly irrigated) in the range of 0.6-2.0%. © 2013 American Water Resources Association. Source

Senger R.,INTERA Incorporated | Romero E.,Polytechnic University of Catalonia | Ferrari A.,Ecole Polytechnique Federale de Lausanne | Marschall P.,National Cooperative for the Disposal of Radioactive Waste
Geological Society Special Publication | Year: 2014

For the characterization of gas migration through a low-permeability clay host rock for deep underground repositories, a comprehensive understanding of the relevant phenomena of gas and fluid flow through low-permeability clay is required. The National Cooperative for the Disposal of Radioactive Waste (Nagra) in Switzerland has developed a comprehensive programme to characterize gas flow in low-permeability Opalinus Clay through laboratory tests and detailed numerical analyses for developing appropriate constitutive models. Laboratory tests were performed on cores by two different laboratories, the Laboratory for Soil Mechanics at EPFL and the Department of Geotechnical Engineering and Geosciences at UPC. Loading tests were performed by both laboratories to study rock compressibility at different stress levels and water permeability dependence on void ratio. The water retention behaviour demonstrated by EPFL and UPC produced comparable results. Water permeability tests and fast controlled-volume air injection experiments were performed in a triaxial cell under isotropic stress conditions on two samples with flow parallel and normal to the bedding planes. A confining stress of 15 MPa was applied during gas testing, corresponding to a lithostatic pressure at a depth of c. 600 m below ground. For detailed analyses, the two-phase flow code TOUGH2 (Pruess et al. 1999) was used. This considers fluid flow in both liquid and gas phases under the influence of pressure, viscous and gravity forces, according to Darcy's law. The standard analyses could not reproduce the measured pressure responses well, and the calibrated hydraulic and two-phase parameters were not consistent with the preceding water test and laboratory analyses. Implementing the non-linear behaviour in terms of the observed relationship between changes in void ratio and associated changes in permeability under different stress conditions significantly improved the simulated results, resulting in a conceptual model that well reproduced the observed injection pressure and outflow responses for both tests, parallel and normal to bedding, using a consistent parameter set. © The Geological Society of London 2014. Source

Lanyon G.W.,Fracture Systems Ltd. | Senger R.,INTERA Incorporated
Transport in Porous Media | Year: 2011

The generation, accumulation, and release of corrosion gases is an important issue in the assessment of long-term repository performance. For repository concepts in clay-rich rock formations such as the Opalinus Clay of Northern Switzerland the transport path through the Excavation Damage Zone (EDZ) around the emplacement tunnels is of particular interest because the gas transport capacity of the host rock is limited and therefore a significant fraction of the produced gas could be released along the EDZ. This article describes the development of a structured approach to abstract complex geoscientific models of two-phase flow through the EDZ to simplified models suitable for use within a Probabilistic Safety Assessment (PSA). The approach utilizes three different models: a discrete fracture network (DFN) model of the EDZ, an equivalent heterogeneous continuum porous medium (CPM) model and a simplified CPM model suitable for use within PSA. Equivalent properties of the elements of the heterogeneous CPM models are upscaled from DFN realizations. Results from gas injection simulations with the heterogeneous CPM models are then used to derive appropriate parameters for the simplified CPM model. The modeling presented in this article represents the first step in the development of a structured methodology for treatment of gas, solute, and water flow through the EDZ. The emphasis is on methodology development, and both input data and structural models used in this study are of a generic nature and would have to be adapted to the actual conditions at a real repository site. © 2011 Springer Science+Business Media B.V. Source

Clemo T.,INTERA Incorporated | Ramarao B.S.,Intera Inc. | Kelly V.A.,Intera Inc. | Lavenue M.,Intera Inc.
World Environmental and Water Resources Congress 2012: Crossing Boundaries, Proceedings of the 2012 Congress | Year: 2012

A recent publication in Ground Water (Sept-Oct., 2010) highlighted the application of capture functions in the management of groundwater, subject to the constraints on the depletion of surface water supplies. Capture maps are used for optimal location of the pumping wells, their rates of withdrawals, and their timing. The computation of capture functions, in the cited paper, is based on perturbation approach with finite differences. An alternative computational strategy for capture functions, based on the adjoint states, is proposed here and is developed for MODFLOW, a groundwater flow simulator. The new methodology is implemented for one of the examples cited in the above paper, namely that of the San Pedro Model, with over 700,000 nodes, developed by the United States Geological Survey, and compared with their results for capture functions based on their perturbation approach. The comparison shows good agreement between the two methods. The proposed adjoint formulation just uses the same computational time, as for one simulation for the heads, and thus saves computational time, relative to the perturbation approach, by a factor equal to the number of nodes in the model, which is of the order of several hundreds of thousands. Because of its immense savings in computational times, this new strategy for the capture functions makes it feasible to embed the groundwater management problem in a stochastic framework (probabilistic approach) to address the uncertainties in the groundwater model. © 2012 ASCE. Source

Intera Inc. and Intera Company | Date: 1996-07-23

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