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Université de Neuchâtel

Conditioning groundwater flow parameters with iterative ensemble smoothers : analysis and approaches in the continuous and the discrete cases

Lam, Dan-Thuy ; Renard, Philippe (Dir.) ; Kerrou, Jaouher (Codir.)

Thèse de doctorat : Université de Neuchâtel, 2019.

Data assimilation (DA) consists in combining observations and predictions of a numerical model to produce an optimal estimate of the evolving state of a system. Over the last decade, DA methods based on the Ensemble Kalman Filter (EnKF) have been particularly explored in various geoscience fields for inverse modelling. Although this type of ensemble methods can handle high-dimensional systems,...

Consortium of Swiss Academic Libraries

New approaches to multi-objective optimization

Grandoni, Fabrizio ; Ravi, R. ; Singh, Mohit ; Zenklusen, Rico

In: Mathematical Programming, 2014, vol. 146, no. 1-2, p. 525-554

Université de Neuchâtel

A geostatistical approach to the simulation of stacked channels

Rongier, G ; Collon, P ; Renard, Philippe

In: Marine and Petroleum Geology, 2017, vol. 82, p. 318-335

Turbiditic channels evolve continuously in relation to erosion-deposition events. They are often gathered into complexes and display various stacking patterns. These patterns have a direct impact on the connectivity of sand-rich deposits. Being able to reproduce them in stochastic simulations is thus of significant importance. We propose a geometrical and descriptive approach to stochastically...

Université de Neuchâtel

Hydrogeological characterization of karst aquifers in Switzerland using a pragmatic approach

Malard, Arnauld ; Jeannin, Pierre-Yves (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2018.

Recent studies reveal that karst aquifers represent a significant part of the Swiss groundwater reserve (120 km3) and resource (8.4 km3/year), although they only extend over 20% of the territory. On the one hand, high infiltration rates and large permeabilities of karstified rocks make karst aquifers highly interesting for water management. On the other hand, karst...

Université de Neuchâtel

Hydrogeological and topographical controls on catchment dynamics and their implications for low flows

Carlier, Claire ; Brunner, Philip (Dir.) ; Hunkeler, Daniel (Codir.)

Thèse de doctorat : Université de Neuchâtel, 2018.

Periods with scarce precipitation will likely occur more frequently and last longer under changing climatic conditions, even in relatively humid regions like Switzerland. To assess the sensitivity of water resources to dry spells and to identify regions that might experience water scarcity issues, a thorough understanding of the mechanisms governing catchment dynamics in the absence of rain is...

Université de Neuchâtel

Stochastic simulation of channelized sedimentary bodies using a constrained L-system

Rongier, G ; Collon, P ; Renard, Philippe

In: Computers & Geosciences, 2017, vol. 105, p. 158-168

Simulating realistic sedimentary bodies while conditioning all the available data is a major topic of research. We present a new method to simulate the channel morphologies resulting from the deposition processes. It relies on a formal grammar system, the Lindenmayer system, or L-system. The L-system puts together channel segments based on user-defined rules and parameters. The succession of...

Université de Neuchâtel

On the use of multiple-point statistics to improve groundwater flow modeling in karst aquifers : A case study from the Hydrogeological Experimental Site of Poitiers, France

Le Coz, M ; Bodin, J ; Renard, Philippe

In: Journal of Hydrology, 2017, vol. 545, p. 109-119

Limestone aquifers often exhibit complex groundwater flow behaviors resulting from depositional heterogeneities and post-lithification fracturing and karstification. In this study, multiple-point statistics (MPS) was applied to reproduce karst features and to improve groundwater flow modeling. For this purpose, MPS realizations were used in a numerical flow model to simulate the responses to...