Olivier Bour

Olivier Bour
Université de Rennes 1 | UR1 · UMR CNRS 6118 - Géosciences Rennes

PhD

About

223
Publications
45,975
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7,676
Citations
Citations since 2016
55 Research Items
4602 Citations
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800
20162017201820192020202120220200400600800

Publications

Publications (223)
Preprint
Full-text available
Essentially all hydrogeological processes are strongly influenced by the subsurface spatial heterogeneity and the temporal variation of environmental conditions, hydraulic properties, and solute concentrations. This spatial and temporal variability needs to be considered when studying hydrogeological processes in order to employ adequate mechanisti...
Article
Full-text available
Exchanges between groundwater and surface water play a key role for ecosystem preservation, especially in headwater catchments where groundwater discharge into streams highly contributes to streamflow generation and maintenance. Despite several decades of research, investigating the spatial variability in groundwater discharge into streams still re...
Article
Full-text available
Active Distributed Temperature Sensing (ADTS) experiments are very useful to provide in-situ and distributed estimates of thermal conductivities of the subsurface and of groundwater flows. However, the data interpretation can be seen as difficult considering the large amount of data collected along a heated fiber-optic cable and the lack of associa...
Article
Modeling heat transfer in complex heterogeneous fractured system is key for geothermal energy applications. Discrete fracture network (DFN) modeling is the classical framework to reproduce the advective part of the transport, which is determined by the fracture connectivity and heterogeneity. This approach in general sacrifices the representation o...
Article
he ultramafic massifs of New Caledonia are mainly composed of regolites with lateritic soils rich in metals such as Co, Fe, Mg and Ni. The nickeliferous ore is exploited by opencast mines. After rainfalls, erosion and particle runoff cause the mobilization of metals and metalloids in surface waters. The objective of this study is (i) to determine t...
Conference Paper
Full-text available
Modeling heat transfer in complex heterogeneous fractured system is key for geothermal energy applications. Discrete fracture network (DFN) modeling is the ideal framework to reproduce the advective part of the transport, which is determined by the fracture connectivity and heterogeneity. This approach in general sacrifices the representation of th...
Preprint
Full-text available
FO-DTS (Fiber Optic Distributed Temperature Sensing) technology has been widely developed to quantify exchanges between groundwater and surface water during the last decade. In this study, we propose, for the first time, to combine long-term passive-DTS measurements and active-DTS measurements in order to highlight their respective potential 10 to...
Article
Fractured aquifers are known to be very heterogeneous with complex flow path geometries. Their characterization and monitoring remain challenging despite the importance to better understand their behavior at all spatial and temporal scales. Heat and correspondingly temperature data have gained much interest in recent years and are often used as a t...
Article
Hydraulic tomography is a state-of-the-art method for inferring hydraulic conductivity fields using head data. We employed geostatistical inversion using synthetically generated head and flux data individually and jointly in a steady-state experiment. We designed 96 inversion scenarios to better understand the relative merits of each data type. For...
Article
Full-text available
We measure groundwater flux and thermal parameters around a borehole performing a heat dissipation test by heating the armor of a single fiber-optic cable and interpreting the resulting heating curves with a new analytical method. The procedure is similar to thermal response tests, but benefitting from the high spatial and temporal resolution of di...
Article
Full-text available
Groundwater flow depends on the heterogeneity of hydraulic properties whose field characterization is challenging. Recently developed active‐Distributed Temperature Sensing (DTS) experiments offer the possibility to directly measure groundwater fluxes resulting from heterogeneous flow fields. Here, based on fundamental principles and numerical simu...
Article
The characterization of saline water intrusion (SWI) and its hydrodynamics is a key issue to understand submarine groundwater discharge (SGD) and manage groundwater resources in coastal areas. To test and compare different methods of characterization and monitoring, a new experimental site has been constructed in a coastal alluvial aquifer north of...
Article
Full-text available
Heat has been used as a tracer to identify and quantify groundwater inflows into streams. Over the last decade, a few methods have used fiber-optic distributed temperature sensing to facilitate assessment of such inflows into small streams. However, these methods focused mainly on the groundwater percentage and the thermal contrast between groundwa...
Article
Full-text available
For many environmental applications, the interpretation of fiber-optic Raman distributed temperature sensing (FO-DTS) measurements is strongly dependent on the spatial resolution of measurements, especially when the objective is to detect temperature variations over small scales. Here, we propose to compare three different and complementary methods...
Poster
Characterization of groundwater/surface water interactions became a key element for the management of water quality and quantity since these exchanges partly control biogeochemical reactivity as well as the distribution and abundance of many freshwater species. However, their quanti􀂦cation is challenging since exchange processes vary both in time a...
Poster
Full-text available
Subsurface characterization often relies on inversion of either pressure or tracer data. Unless data from many pumping and observation wells are available, the inversion process only resolves smooth low-resolution images of subsurface properties, which leads to less accurate subsurface flow and reactive transport predictions. Furthermore, tracer tom...
Article
Full-text available
Experimental characterization of thermal transport in fractured media through thermal tracer tests is crucial for environmental and industrial applications such as the prediction of geothermal system efficiency. However, such experiments have been poorly achieved in fractured rock due to the low permeability and complexity of these media. We have t...
Presentation
As pressure on coastal fresh groundwater resources increases, interest in coastal aquifers monitoring rises. The weakest point of coastal aquifers occurs at the fresh-salt water interface induced by seawater intrusion (SWI), highly sensible to any change in the heads of the fresh and salt water bodies. Therefore, the position, width and dynamics of...
Poster
Full-text available
Large regional numerical models are often used for the prediction of groundwater fluxes to surface water or to assess the impacts of changes in either climate, land use or groundwater exploitation. Such models typically use a large grid size and a low-resolution land surface topography. The objective of our study was to assess if such large models...
Poster
As pressure on coastal fresh groundwater resources increases, interest in coastal aquifers monitoring rises. The weakest point of coastal aquifers occurs at the underground fresh-salt water interface induced by seawater intrusion (SWI), highly sensitive to any change in the heads of the fresh and salt water bodies. SWI is therefore one of the main...
Poster
Full-text available
Heat has been increasingly used as a tracer for characterization of the subsurface media both in fractured and porous aquifers. In fractured wellbore, understanding of the role of each fracture in total production of the fluid and the change of their contribution with change of the system conditions can help us increase our understanding about the...
Article
Full-text available
Observation of hydrological processes has a long-standing tradition covering various climatic, hydrologic, geologic, and geomorphologic conditions. Hydrological observations are either organized in dedicated observatories focused on hydrology or within larger environmental observatories that address processes from the atmosphere to the groundwater....
Article
Full-text available
The French critical zone initiative, called OZCAR (Observatoires de la Zone Critique–Application et Recherche or Critical Zone Observatories–Application and Research) is a National Research Infrastructure (RI). OZCAR-RI is a network of instrumented sites, bringing together 21 pre-existing research observatories monitoring different compartments of...
Article
The modeling and prediction of heat transfer in fractured media is particularly challenging as hydraulic and transport properties depend on a multiscale structure that is difficult to resolve. In addition to advection and dispersion, heat transfer is also impacted by thermal lag time and attenuation, which results from fracture-matrix thermal excha...
Article
Full-text available
Thermal response tests are used to assess the subsurface thermal conductivity to design ground-coupled heat pump systems. Conventional tests are cumbersome and require a source of high power to heat water circulating in a pilot ground heat exchanger. An alternative test method using heating cable was verified in the field as an option to conduct th...
Article
Fracture-scale heterogeneity plays an important role in driving dispersion, mixing and heat transfer in fractured rocks. Current approaches to characterize fracture scale flow and transport processes largely rely on indirect information based on the interpretation of tracer tests. Geophysical techniques used in parallel with tracer tests can offer...
Article
Crystalline rocks are in general considered of poor interest for geothermal applications at shallow depths (<100 m), in particular because of their low permeability. In some cases, fractures may enhance permeability, but thermal energy storage at these shallow depths still remains challenging because of the complexity of fractured media to efficien...
Presentation
Direct measurement of groundwater flux is desirable for the quantitative and qualitative monitoring of coastal aquifers, for understanding processes at the fresh-salt water interface and for estimating submarine groundwater discharge. Traditionally, hydraulic conductivity was measured in order to estimate flow rates. Instead, this research propose...
Poster
Full-text available
To overcome water scarcity issues, Managed Aquifer Recharge (MAR) structures are currently developed in many parts of the world, including poorly permeable terrain like weathered crystalline rocks. In such geological context, characterized by relatively limited groundwater storage mainly associated with fractures located at the interface between th...
Poster
Understanding and quantifying groundwater and surface water interactions are key elements for the management of water quality and quantity but also for the preservation of groundwater dependent ecosystems and riparian habitat. Localizing and quantifying these exchanges remains challenging since exchange processes vary both in time and space leading...
Article
We investigate denitrification mechanisms through batch experiments using crushed rock and groundwater from a granitic aquifer subject to long term pumping (Ploemeur, France). Except for sterilized experiments, extensive denitrification reaction induces NO3 decreases ranging from 0.3 to 0.6 mmol/L. Carbon concentrations, either organic or inorganic...
Article
We investigated the mixing and dynamic of denitrification processes induced by long-term pumping in the crystalline aquifer of Ploemeur (Brittany, France). Hydrological and geochemical parameters have been continuously recorded over 15 boreholes in 5km(2) on a 25-year period. This extensive spatial and temporal monitoring of conservative as well as...
Article
Flow through reservoirs such as fractured media is powered by head gradients which also generate measurable poroelastic deformation of the rock body. The combined analysis of surface deformation and sub-surface pressure provides valuable insights of a reservoir's structure and hydromechanical properties, which are of interest for deep-seated CO2 or...
Article
In fractured media, solute transport is controlled by advection in open and connected fractures and by matrix diffusion that may be enhanced by chemical weathering of the fracture walls. These phenomena may lead to non-Fickian dispersion characterized by early tracer arrival time, late-time tailing on the breakthrough curves and potential scale eff...
Article
Fractured bedrock reservoirs are of socio-economical importance, as they may be used for storage or retrieval of fluids and energy. In particular, the hydromechanical behavior of fractures needs to be understood as it has implications on flow and governs stability issues (e.g. microseismicity). Laboratory, numerical or field experiments have brough...
Poster
Understanding and quantifying groundwater and surface water interactions are key elements for the management of water quality and quantity, but also for the preservation of groundwater dependent ecosystems and riparian habitat. We developed a methodology to quantify groundwater and surface water interactions, by setting up an active heat tracer exp...
Article
Electrical and electromagnetic methods are extensively used to map electrically conductive tracers within hydrogeologic systems. Often, the tracers used consist of dissolved salt in water, leading to a denser mixture than the ambient formation water. Density effects are often ignored and rarely modeled, but can dramatically affect transport behavio...
Article
Full-text available
In the perspective of a temporal and spatial exploration of aquatic environments (surface and ground water), we developed a technique for field continuous measurements of dissolved gases with a precision better than 1% for N2, O2, CO2, He, Ar, 2% for Kr, 8% for Xe and 3% for CH4, N2O and Ne. With a large resolution (from 1×10(-9) to 1×10(-2) ccSTP/...
Article
Full-text available
Distributed Temperature Sensing (DTS) technology enables down-hole temperature monitoring to study hydrogeological processes at unprecedentedly high frequency and spatial resolution. DTS has been widely applied in passive mode in site investigations of groundwater flow, in-well flow, and subsurface thermal property estimation. However, recent years...
Presentation
Estimation of groundwater flow is a key element for the quantitative and qualitative monitoring of groundwater resources. Continued monitoring of groundwater flux should help to manage unconsolidated coastal aquifers, which is our motivation. We propose using Fiber-Optic Distributed Temperature Sensing (FODTS) as a new approach to measure groundwat...
Article
While groundwater constitutes a crucial resource in many crystalline-rock regions worldwide, well-yield conditions are highly variable and barely understood. Nevertheless, it is well known that fault zones may have the capacity to ensure sustainable yield in crystalline media, but there are only a few and disparate examples in the literature that d...
Article
The characterization and modeling of heat transfer in fractured media is particularly challenging as the existence of fractures at multiple scales induces highly localized flow patterns. From a theoretical and numerical analysis of heat transfer in simple conceptual models of fractured media, we show that flow channeling has a significant effect on...
Poster
Geothermal energy is a renewable energy source particularly attractive due to associated low greenhouse gas emission rates. Crystalline rocks are in general considered of poor interest for geothermal applications at shallow depths (< 100m), because of the low permeability of the medium. In some cases, fractures may enhance permeability, but thermal...
Poster
Understand the dynamics of the fresh-salt water interface in aquifers is a key issue to comprehend mixing process and to quantity the discharge of nutrients in to coastal areas. In order to go beyond the current knowledge in this issue an experimental site has been set up at the alluvial aquifer Riera Argentona (Barcelona – Spain). The site compris...
Article
The in situ characterization of transport processes in fractured media is particularly challenging due to the considerable spatial uncertainty on tracer pathways and dominant controlling processes, such as dispersion, channeling, trapping, matrix diffusion, ambient and density driven flows. We attempted to reduce this uncertainty by coupling push-p...
Poster
Geothermal energy is a renewable energy source particularly attractive due to associated low greenhouse gas emission rates. Crystalline rocks are in general considered of poor interest for geothermal applications at shallow depths (< 100m), because of the low permeability of the medium. In some cases, fractures may enhance permeability, but thermal...
Article
Fractured aquifers which bear valuable water resources are often difficult to characterize with classical hydrogeological tools due to their intrinsic heterogeneities. Here, we implement ground surface deformation tools (tiltmetry and optical leveling) to monitor groundwater pressure changes induced by a classical hydraulic test at the Ploemeur obs...
Article
Full-text available
Measurement of groundwater fluxes is the basis of all hydrogeological study, from hydraulic characterization to the most advanced reactive transport modeling. Usual groundwater flux estimation with Darcy's law may lead to cumulated errors on spatial variability, especially in fractured aquifers where local direct measurement of groundwater fluxes b...
Article
Full-text available
We develop an approach for measuring in-well fluid velocities using point electrical heating combined with spatially and temporally continuous temperature monitoring using distributed temperature sensing (DTS). The method uses a point heater to warm a discrete volume of water. The rate of advection of this plume, once the heating is stopped, equate...
Article
Full-text available
Climate change is thought to have major effects on groundwater resources. There is however a limited knowledge of the impacts of past climate changes such as warm or glacial periods on groundwater although marine or glacial fluids may have circulated in basements during these periods. Geochemical investigations of groundwater at shallow depth (80-4...
Article
Full-text available
We develop an approach for measuring in-well fluid velocities using point electrical heating combined with spatially and temporally continuous temperature monitoring using Distributed Temperature Sensing (DTS). The method uses a point heater to warm a discrete volume of water. The rate of advection of this plume, once the heating is stopped, equate...
Conference Paper
Full-text available
Les distributions des temps de transit jouent un rôle central dans les processus de transport, dans l’interprétation des traceurs anthropogéniques ainsi que dans les prédictions portant sur les ressources en eau souterraine dans les aquifères de socle. Cependant elles ne sont pas accessibles directement à l’aide de mesures de terrain. Seules certai...