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Université de Neuchâtel

Posterior population expansion for solving inverse problems

Jäggli, C ; Straubhaar, J ; Renard, Philippe

In: Water Resources Research, 2017, vol. 53, p. 2902-2916

Solving inverse problems in a complex, geologically realistic, and discrete model space and from a sparse set of observations is a very challenging task. Extensive exploration by Markov chain Monte Carlo (McMC) methods often results in considerable computational efforts. Most optimization methods, on the other hand, are limited to linear (continuous) model spaces and the minimization of an...

Université de Neuchâtel

Advances in understanding river-groundwater interactions

Brunner, Philip ; Therrien, R ; Renard, Philippe ; Simmons, C.T ; Hendricks Franssen, H-J

In: Reviews of Geophysics, 2017, vol. 55, p. 818-854

River-groundwater interactions are at the core of a wide range of major contemporary challenges, including the provision of high-quality drinking water in sufficient quantities, the loss of biodiversity in river ecosystems, or the management of environmental flow regimes. This paper reviews state of the art approaches in characterizing and modeling river and groundwater interactions. Our review...

Université de Neuchâtel

Simulating Small-Scale Rainfall Fields Conditioned by Weather State and Elevation : A Data-Driven Approach Based on Rainfall Radar Images

Oriani, F ; Ohana-Levi, N ; Marra, F ; Straubhaar, J ; Mariethoz, Gregoire ; Renard, Philippe ; Karnieli, A ; Morin, E

In: Water Resources Research, 2017, vol. 53, p. 8512-8532

The quantification of spatial rainfall is critical for distributed hydrological modeling. Rainfall spatial patterns generated by similar weather conditions can be extremely diverse. This variability can have a significant impact on hydrological processes. Stochastic simulation allows generating multiple realizations of spatial rainfall or filling missing data. The simulated data can then be used...

Université de Neuchâtel

Stochastic fracture generation accounting for the stratification orientation in a folded environment based on an implicit geological model

Borghi, Andrea ; Renard, Philippe ; Fournier, L ; Negro, François

In: Engineering Geology, 2015, vol. 187, p. 135-142

This paper presents a new approach in generating stochastic discrete fracture networks. The particularity of the approach is that it allows us to simulate the theoretical families of fractures that are expected in a folded environment. The approach produces fractures that are consistent with the local stratigraphic orientation. The fractures are modeled as simple rectangular planar objects. When...

Université de Neuchâtel

An optical laser device for mapping 3D geometry of underwater karst structures : first tests in the Ox Bel’Ha system, Yucatan, Mexico = Un dispositivo láser óptico para la cartografía 3D de la geometría de estructuras kársticas submarinas: primeros resultados en el sistema de Ox Bel’Ha, Yucatán, México

Schiller, A ; Renard, Philippe

In: Boletin Geológico y Minero, 2016, vol. 127, no. 1, p. 99-110

In the course of extended hydrological studies in the coastal Karst plain of Yucatan, near the town of Tulum amongst others, a novel laser scanning device was developed and applied for the acquisition of the 3d-geometry of ground water conduits. The method is derived from similar industrial systems and for the first time adapted to the specific measurement conditions in underwater cave systems....

Université de Neuchâtel

Generation of 3D Spatially Variable Anisotropy for Groundwater Flow Simulations

Borghi, Andrea ; Renard, Philippe ; Courrioux, Gabriel

In: Groundwater, 2015, vol. 53, no. 6, p. 955-958

Sedimentary units generally present anisotropy in their hydraulic properties, with higher hydraulic conductivity along bedding planes, rather than perpendicular to them. This common property leads to a modeling challenge if the sedimentary structure is folded. In this paper, we show that the gradient of the geological potential used by implicit geological modeling techniques can be used to...

Université de Neuchâtel

Conditioning multiple-point statistics simulations to block data

Straubhaar, J ; Renard, Philippe ; Mariethoz, Gregoire

In: Spatial Statistics, 2016, vol. 16, p. 53-71

Multiple-points statistics (MPS) allows to generate random fields reproducing spatial statistics derived from a training image. MPS methods consist in borrowing patterns from the training set. Therefore, the simulation domain is assumed to be at the same resolution as the conceptual model, although geometrical deformations can be handled by such techniques. Whereas punctual conditioning data...

Université de Neuchâtel

Impact of a stochastic sequential initiation of fractures on the spatial correlations and connectivity of discrete fracture networks

Bonneau, F ; Caumon, G ; Renard, Philippe

In: Journal of Geophysical Research: Solid Earth, 2016, vol. 121, no. 8, p. 5641-5658

Stochastic discrete fracture networks (DFNs) are classically simulated using stochastic point processes which neglect mechanical interactions between fractures and yield a low spatial correlation in a network. We propose a sequential parent-daughter Poisson point process that organizes fracture objects according to mechanical interactions while honoring statistical characterization data. The...

Université de Neuchâtel

Missing data simulation inside flow rate time-series using multiple-point statistics

Oriani, F ; Borghi, A ; Straubhaar, J ; Mariethoz, Grégoire ; Renard, Philippe

In: Environmental Modelling & Software, 2016, vol. 86, p. 264-276

The direct sampling (DS) multiple-point statistical technique is proposed as a non-parametric missing data simulator for hydrological flow rate time-series. The algorithm makes use of the patterns contained inside a training data set to reproduce the complexity of the missing data. The proposed setup is tested in the reconstruction of a flow rate time-series while considering several missing data...

Université de Neuchâtel

Integrating aerial geophysical data in multiple-point statistics simulations to assist groundwater flow models

Dickson, N.E.M ; Comte, J.-C ; Renard, Philippe ; Straubhaar, J ; McKinley, J.M ; Ofterdinger, U

In: Hydrogeology Journal, 2015, vol. 23, no. 5, p. 883-900

The process of accounting for heterogeneity has made significant advances in statistical research, primarily in the framework of stochastic analysis and the development of multiple-point statistics (MPS). Among MPS techniques, the direct sampling (DS) method is tested to determine its ability to delineate heterogeneity from aerial magnetics data in a regional sandstone aquifer intruded by...