Beauce Aquifer Research Articles

Hydrogeophysical characterization and determination of petrophysical parameters by integrating geophysical and hydrogeological data at the limestone vadose zone of the Beauce aquifer

The hydrological characterization of the vadose zone remains a major challenge considering the spatiotemporal variability of its properties and the limitations associated with hydrological measurements techniques. Geophysical methods, in particular the DC-resistivity and ground penetrating radar, can provide large scale images of hydrogeological structures and a non-invasive assessment of the subsurface dynamic processes. However, these approaches rely on the accuracy of the petrophysical relationships connecting the geophysical parameters to hydrogeological ones, where the site-specific determination of the associated petrophysical parameters is considered crucial. The first objective of this study was to investigate the relationship between the water content, geological properties, and geophysical attributes at the vadose zone of a vulnerable limestone aquifer. The second objective aimed to obtain the Archie’s and Complex Refractive Index Model (CRIM) petrophysical parameters by using borehole electrical resistivity and cross-hole ground penetrating radar data. For this purpose, we adopted a grid search inversion algorithm where the field geophysical data were integrated with water content profiles simulated by using HYDRUS-1D. The vadose zone profile was divided into three layers, and the inversion was carried out for the petrophysical parameters in each of the model layers. The electrical resistivity and relative dielectric permittivity data showed a very good correspondence with the simulated and experimental water content distributions along the vadose zone profile. The petrophysical parameters estimated by the inversion showed values that fall in the ranges reported in the literature. Similar values have been observed in the different model layers, with slight differences that were attributed to the vertical heterogeneities associated with the alteration and fracturation features of the limestone vadose zone. This study showed a very good correlation between geophysical, hydrogeological and geological data, and highlighted the presence of heterogeneities that can have profound effects on the vadose zone water dynamics.

Indirect emissions of nitrous oxide in a cropland watershed with contrasting hydrology in central France

Nitrous oxide (N2O) is an important greenhouse gas. Its atmospheric concentration have increased with the industrialisation and the use of N fertilizer. The contribution of freshwater systems to N2O emissions is still very uncertain, while regional transfer of nitrogen depends on soil and hydrology. Riverine and spring N2O dissolved in water was therefore measured over two years in the 3453 km2 Haut-Loir watershed (France). This temperate cropland watershed is characterized by two different hydrological systems east and west of the Loir River. The eastern rivers, fed by the emergence of the deep Beauce aquifer, exhibited significantly higher dissolved N2O concentrations (Beauce region, mean: 2.93 μg-N L−1) than the western rivers (Perche region, mean: 0.87 μg-N L−1), which were largely influenced by runoff during winter flooding. The eastern rivers had large nitrate concentrations all over the year; in the Perche, nitrate underwent a seasonal cycle with large loads during winter floods, but there were no consistent seasonal patterns in N2O. The ratios of N2O in excess of equilibrium on nitrate, often used as a proxy of emission factor (EF), were much smaller than the default IPCC values, both for rivers (0.014% versus 0.25% for IPCC EF5r) and the Loir spring (0.085% versus 0.6% for the IPCC EF5g for groundwater and springs). EF5r were significantly different between the two parts of the watershed only in winter, because of the seasonal variability of NO3−. Moreover dissolved N2O is controlled not only by NO3−, as it is considered in the calculation of the EF5, but also by water pH and dissolved organic carbon. A good prediction of dissolved N2O was obtained using these physicochemical variables and hydrological regions. Thus, these results suggest that the spatial variability of riverine N2O depends on local hydrology, while further research is needed to understand the seasonal variability.

A dynamic model of irrigation and land-use choice: application to the Beauce aquifer in France

We set up a model of land-use and irrigation water choices to assess the impact of dry weather conditions and possible restriction policies on farmers' payoffs in the Beauce area in France. Given the informational context, we construct a dynamic two-period model in which farmers make conjectures on the water abstraction by other users and take into account variations in the height of the water table. We solve the problem using dynamic programming. We simulate different restriction policies, proposed in the literature and tested in the field. We show that these restrictions, although efficient with respect to hydrological criteria, result in serious economic losses for the farmers.

Quantification of the contribution of the Beauce groundwater aquifer to the discharge of the Loire River using thermal infrared satellite imaging

Abstract. Seven Landsat thermal infrared (TIR) images taken over the period 2000–2010 were used to establish longitudinal temperature profiles of the middle Loire River where it flows above the Beauce aquifer. The groundwater discharge along the river course was quantified for each identified groundwater catchment area using a heat budget based on temperature variations of the Loire River estimated from the TIR images. The results showed that 75 % of the temperature differences, between in situ observations and TIR image-based estimations, remained within the ±1 °C interval. The main discharge area of the Beauce aquifer into the Loire River was located between river kilometers 630 and 650, where there was a temperature drop of 1–1.5 °C in the summer and a rise of 0.5 °C in winter. According to the heat budgets, groundwater discharge was higher during the winter period (13.5 m3 s−1) than during the summer period (5.3 m3 s−1). These findings are in line with the results of both a groundwater budget and a process-based distributed hydrogeological model. Groundwater input was also found to be higher during the Loire's flow recession periods.

Hybrid fitting of a hydrosystem model: Long‐term insight into the Beauce aquifer functioning (France)

This study aims at analyzing the water budget of the unconfined Beauce aquifer (8000 km2) over a 35 year period, by modeling the hydrological functioning and quantifying exchanged water fluxes inside the system. A distributed process‐based model (DPBM) is implemented to model the surface, the unsaturated zone and the aquifer subsystems. Based on an extensive literature review on multiparameter optimization and inverse problem, a pragmatic hybrid fitting method that couples manual and automatic calibration is developed. Three data subsets are used for calibration (10 year), validation (10 year) and test (35 year). The global piezometric head root‐mean‐square error is around 2.5 m for the three subsets and is rather uniformly spatially distributed over 78 piezometers. The sensitivity of the simulation to the different steps of the calibration process is investigated. The transmissivity field permits the fitting of the low‐frequency signal for long‐term filtering of the recharge signal, whereas the storage coefficient filters the signal with a higher frequency. For long‐term insight into aquifer system functioning, the priority is thus to first fit the transmissivity field and to assess the distributed aquifer recharge accurately. The fitted DPBM, coupled with a linear model of coregionalization, is then used to quantify the hydrosystem water mass balance between 1974 and 2009, indicating that there is yet no trend of water resources decrease neither due to climate nor to human activities.

Evaluation of irrigation strategies in partnership in the case of withdrawal limitations in the Beauce aquifer (France)

The Beauce aquifer (France) is one of the few subjected to volumetric management resulting from a negotiation between farmers and the administration. Since 1999, a quota has been allocated to each of the 3,600 irrigated farms located on six administrative counties. Each year, quotas are weighted by a coefficient of reduction linked to the average piezometric level. The decrease in the level since 2003 has led to a reduction of withdrawal permission with uncertainties for the future. This paper presents an approach developed with actors to analyze their adaptations and the agronomic and economic consequences of a thus far hypothetical substantial reduction in irrigation quantities.

Un regard rétrospectif sur l'évolution de la gouvernance de l'irrigation en Beauce (1993-2008)

A retrospective look at the evolution of irrigation governance in the Beauce area (1993-2008) The calcareous Beauce aquifer, located to the West of Paris, has a quite peculiar administrative position. Because this aquifer is one of the most important of France in terms of volume and needs, the institutions related to its management have different responsibilities causing conflicts of interest at all levels of the hierarchical governance structure. More precisely, the aquifer occupies six local departments, two regions and two regional water basins. Conflicts arising from water quality degradation and a three-year period of dramatic drought, coupled with an important increase in the pumping of water for irrigation, has increased social awareness regarding the sustainability of this resource. This article studies the institutional process of water management implemented over the last fifteen years. After a brief history of the administrative measures adopted since the mid-90’s, we study the emergence of a multi-stakeholder procedure, namely the SAGE process, and some of the voluntary measures which have emerged from the context of conflict between irrigators and NGO’s. This study helps us to identify the governance of the Beauce Aquifer as a compromise between Collective Action for Public Interest and Collective Action for Community Interest.

Water temperature behaviour in the River Loire since 1976 and 1881

Analysis of monthly mean river temperatures, recorded on an hourly basis in the middle reaches of the Loire since 1976, allows reconstruction by multiple linear regression of the annual, spring and summer water temperatures from equivalent information on air temperatures and river discharge. Since 1881, the average annual and summer temperatures of the Loire have risen by approximately 0.8 °C, this increase accelerating since the late 1980s due to the rise in air temperature and also to lower discharge rates. In addition, the thermal regime in the Orleans to Blois reach is considerably affected by the inflow of groundwater from the Calcaires de Beauce aquifer, as shown by the summer energy balance. To cite this article: F. Moatar, J. Gailhard, C. R. Geoscience 338 (2006).

Gestion durable d'une ressource en eaux souterraines Cas de la nappe de Beauce

The Beauce aquifer (9000 km 2 ) is one of the main aquifers in France and plays an essential role for the rivers recharge, the drinking water supply and the ecconomic activities. The increasing pressure of agriculture, together with dry periods lead to a lack of balance and to hard tenseness. A global management of the resources with the concerned partners was set up; the elaboration of a SAGE has been programmed.

Modèle d'eutrophisation de la Loire Moyenne / Eutrophication model for the middle reaches of the Loire

Abstract In order to evaluate the impact of nuclear or hydraulic works upon the middle reaches of the Loire, an ecological model is constructed and applied to the River Loire between the confluence of the River Allier and the city of Blois. This model simulates a simplified ecosystem near to a state of eutrophication. The state variables are the phytoplankton, the zooplankton and the nutrients, nitrogen or phosphorus. The input data to the system are three-hourly average values of incoming solar radiation, and the daily values of flow and water temperature. The application to the River Loire is restricted to phytoplankton, nitrogen and phosphorus. The model is calibrated with weekly data measured in 1974 and 1975 at the Saint-Laurent-des-Eaux nuclear power plant, after the values of nitrogen and phosphorus input from the population bordering the river, from fertilizers spread over the basin and from the springs of the Beauce aquifer had been separately evaluated.