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Distributed temperature sensing is known to provide sharp signals which are very efficient for mapping hydraulically active fractures in wellbores. High-resolution temperature sensing has specifically demonstrated its capacity to characterize very low flows in wellbores. But as sharp as they can be, temperature profiles are often difficult to decipher. The aim of the present work is to provide and to test the “Borehole Heat Budget Calculator” (BHB Calculator), which is implemented as a fast and easy to use tool for the quantitative analysis of depth-temperature profiles. The Calculator is suitable for most pumping and draining configurations, as the heat budget is generalized for modelling multidirectional flow systems within the same wellbore. The formatted worksheet allows the quick exploitation of temperature logs, and is applicable for the characterization of distributed fractures in long screened wellbores. Objectives of the heat modelling are to enhance the readability of complex depth-temperature data, as well as to quantify distribution of inflow intensities and temperatures with depth. The use of heat budget helps to clearly visualize how heat conduction and heat advection contributions are distributed along wellbores profiles. Calculations of inflow temperatures and their evolution through pumping duration is a prerequisite to infer about the nature of aquifer properties (i.e. conduits, distributed or discrete fractures, porous media), as well as to give insight information about the mapping of effective flow paths draining the aquifer. The efficiency and limitations of the BHB Calculator are being tested through high-resolution temperature logging, along with complementary flowmetering and televiewing logging in fractured aquifers located in the St-Lawrence Lowlands, Quebec, Canada.

Summary A new hydrogeologic model is developed for the Plateau de Saclay (20 km south-west of Paris, France), which covers an area of 74 km 2 . It is based on a 2D model of the Fontainebleau Sands aquifer, combined with a 1D model of the unsaturated zone, taking into account the spatial variability of the groundwater permeability field and the thickness of the unsaturated zone. The paper focuses on the estimation of a triplet of parameters (permeability, infiltration and effective porosity), based on transient flow simulations. First, the permeability is obtained by inversion of mean hydraulic head data for different values of infiltration. Then, infiltration and effective porosity are determined by using transient flow simulations and fitting the hydraulic head measurements at several piezometers over the 1970–2014 period. The infiltration is estimated at between 125 and 150 mm/yr, the mean permeability between 2 · 10 −5 and 6 · 10 −5 m/s, and the effective porosity between 20% and 30%. Furthermore, the role of the unsaturated zone is quantified and the induced delay is estimated at about 20 years in the case of the transport of a tracer.

International audience; This work aims to provide an overview of the thermal processes that shape wellbore temperature profiles under static and dynamicconditions. Understanding of the respective influences of advection and conduction heat fluxes is improved through the useof a new heat budget at the borehole scale. Keeping in mind the thermal processes involved, a qualitative interpretation of thetemperature profiles allows the occurrence, the position, and the origin of groundwater flowing into wellbores from hydraulicallyactive fractures to be constrained.With the use of a heat budget developed at the borehole scale, temperature logging efficiency hasbeen quantitatively enhanced and allows inflow temperatures to be calculated through the simultaneous use of a flowmeter. Undercertain hydraulic or pumping conditions, both inflow intensities and associated temperatures can also be directly modelled fromtemperature data and the use of the heat budget. Theoretical and applied examples of the heat budget application are provided.Applied examples are shown using high-resolution temperature logging, spinner flow metering, and televiewing for three wellsinstalled in fractured bedrock aquifers in the St-Lawrence Lowlands, Quebec, Canada. Through relatively rapid manipulations,thermal measurements in such cases can be used to detect the intervals or discrete positions of hydraulically active fractures inwellbores, as well as the existence of ambient flows with a high degree of sensitivity, even at very low flows. Heat budget calculationsat the borehole scale during pumping indicate that heat advection fluxes rapidly dominate over heat conduction fluxes with theborehole wall. The full characterization of inflow intensities provides information about the distribution of hydraulic propertieswith depth. The full knowledge of inflow temperatures indicates horizons that are drained from within the aquifer, providingadvantageous information on the depth from which groundwater originates during pumping.1. Introduction

International audience; Karst aquifers are characterized by a strong heterogeneity in their physical properties. The purpose of the study is the spatial variability of water transfers in a carbonated karstic aquifer. To this end, a high spatial density of information about the water transfer is needed. The characteristics of the site, a topographic hill of 13 km2 with eight boreholes, which was monitored hourly over four years, allows the study of the spatial variability of water transfers. The variability of the impulse response of the system is studied using autocorrelation and cross-correlation analysis between the rainfall and piezometric level time series. The shapes of the autocorrelation and cross-correlation functions vary according to the geographical location of the boreholes, that proves a spatial organization of the groundwater transfer. The response time varies depending on the thickness of the unsaturated zone by an unusual inverse correlation. In this case, the water level signal spatially integrates the signal transfer of the unsaturated zone and the signal transfer of the saturated part of the aquifer. Consequently, inertia and response time increased with the distance between the borehole and the top of piezometric dome. This description supports highly organized fast transfers in this karst aquifer and a highly connected fracture network.

International audience; We study the temporal variability of water transfer through the infiltration zone of a karst aquifer by estimating the impulse response of the system using cross-correlogram analyses between rainfall and piezometric level time series. We apply a sliding-window cross-correlation method, which calculates cross-correlograms on partially superposed short time series windows. We apply this method for rainfall and piezometric level time series at six boreholes in a fractured karstic aquifer located in Burgundy, France. Based on cross-correlogram functions, we obtain a time series of response time. At most of the boreholes, the cross-correlation functions change over time, and the response times vary seasonally, being shorter during the summer. This unusual structure can be partly explained by the seasonal variability in rainfall intensity, which is higher during the summer (May–September), inducing the seasonal behaviour of the epikarst. During the summer, when rainfall intensity is higher, the epikarst is more easily and quickly saturated. This induces an increase in lateral water transfer within the epikarst and an increase in concentrated fast flows. We also show that the response time seems to tend towards a limit which represents the maximum saturation of the epikarst.