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Avignon, France

Baudron P.,CIRAD - Agricultural Research for Development | Barbecot F.,GEOTOP UQAM | Barbecot F.,University Paris - Sud | Arostegui J.L.G.,Instituto Geologico Y Minero Of Espana | And 4 more authors.
Hydrological Processes | Year: 2014

The development of intense agriculture in semiarid areas modifies intensity and spatial distribution of groundwater recharge by summing irrigation return flow to limited rainfall infiltration. Environmental tracers provide key information, but their interpretation is complicated by more complex groundwater flow patterns. In multilayered aquifers, the real origin of the groundwater samples is hard to assess because of local mixing processes occurring inside long-screened boreholes. We use environmental tracers (14C, 13C, 2H, 18O, 3H) to investigate the long-term evolution of recharge in the five-layer Campo de Cartagena aquifer in South-Eastern Spain, in addition to high-resolution temperature loggings to identify the depth of origin of groundwater. Despite the complex background, this methodology allowed a reliable interpretation of the geochemistry and provided a better understanding of the groundwater flow patterns. The tritium method did not give good quantitative results because of the high variability of the recharge signal but remained an excellent indicator of recent recharge. Nonetheless, both pre-anthropization and post-anthropization recharge regime could be identified and quantified by radiocarbon. Before the development of agriculture, recharge varied from 17mm. year-1 at the mountain ranges to 6mm. year-1 in the plain, whereas the mean annual rainfall is about 300mm. In response to the increase of agricultural activity, recharge fluxes to the plain were amplified and nowadays reach up to 210mm. year-1 in irrigated areas. These values are strengthened by global water budget and local unsaturated zone studies. © 2013 John Wiley & Sons, Ltd.


Henry S.,University of Oxford | Pozzo Di Borgo E.,UAPV | Cavaillou A.,French National Institute for Agricultural Research | Cavaillou A.,French National Center for Scientific Research
Review of Scientific Instruments | Year: 2013

SQUIDs can be used to monitor the three vector components of the geomagnetic field to a high precision at very low frequencies, yet as they are susceptible to external interference, the accuracy to which they can track changes in the dc field over long periods has been unclear. We have carried out simultaneous measurements of the geomagnetic field recorded using two independent 3-axis SQUID magnetometers at the Laboratoire Souterrain à Bas Bruit (LSBB). We demonstrate a technique to take the difference between a linear transform of the three signals from one magnetometer, and a reference signal from the other, in order to account for any difference in alignment and calibration, and track local signals at a sub-nT level. We confirmed that both systems tracked the same signal with an RMS difference as low as 56pT over a period of 72 h. To our knowledge this is the first such demonstration of the long term accuracy of SQUID magnetometers for monitoring geomagnetic fields. © 2013 American Institute of Physics.


Jourde H.,Montpellier University | Mazzilli N.,UAPV | Mazzilli N.,French National Institute for Agricultural Research | Lecoq N.,University of Rouen | And 2 more authors.
Environmental Earth Sciences | Year: 2015

On the basis of the characterization of the different karst subsystems (Soil/Epikarst—Unsaturated Zone—Saturated Zone) and mathematical models developed on specific sites, we propose an adjustable modeling platform of karst for both the simulation of spring discharge at outlets and the analysis of the hydrodynamics of the compartments considered in the model. This platform was developed within the framework of the KARST observatory network initiative from the INSU/CNRS, which aims to strengthen knowledge-sharing and promote cross-disciplinary research on karst systems at the national scale. © Springer-Verlag Berlin Heidelberg 2015.


Capowiez Y.,French National Institute for Agricultural Research | Bottinelli N.,IRD Montpellier | Sammartino S.,UAPV | Michel E.,French National Institute for Agricultural Research | And 2 more authors.
Biology and Fertility of Soils | Year: 2015

Earthworm burrow systems are generally described based on postulated behaviours associated with the three ecological types. In this study, we used X-ray tomography to obtain 3D information on the burrowing behaviour of six very common anecic (Aporrectodea nocturna and Lumbricus terrestris) and endogeic (Aporrectodea rosea, Allolobophora chlorotica, Aporrectodea caliginosa, Aporrectodea icterica) earthworm species, introduced into repacked soil cores for 6 weeks. A simple water infiltration test, the Beerkan method, was also used to assess some functional properties of these burrow systems. Endogeic worms make larger burrow systems, which are more highly branched, less continuous and of smaller diameter, than those of anecic worms. Among the anecic species, L. terrestris burrow systems are shorter (9.2 vs 21.2 m) with a higher number (14.5 vs 23.5) of less branched burrows (12.2 vs 20.2 branches m−1), which are also wider (7.78 vs 5.16 mm) than those of A. nocturna. In comparison, the burrow systems made by endogeic species appeared similar to each other. However, A. rosea burrows were short and narrow, whereas A. icterica had a longer burrow system (15.7 m), more intense bioturbation intensity (refilled macropores or soil lateral compaction around them) and thus a greater number of burrows. Regarding water infiltration, anecic burrow systems were far more efficient due to open burrows linking the top and bottom of the cores. For endogeic species, we observed a linear relationship between burrow length and the water infiltration rate (R2 = 0.49, p < 0.01). Overall, the three main characteristics significantly influencing water infiltration were burrow length, burrow number and bioturbation volume. This last characteristic highlighted the effect of burrow refilling by casts. © 2015, Springer-Verlag Berlin Heidelberg.


Sammartino S.,UAPV | Lissy A.-S.,French National Institute for Agricultural Research | Bogner C.,University of Bayreuth | Van Den Bogaert R.,French National Institute for Agricultural Research | And 3 more authors.
Vadose Zone Journal | Year: 2015

Understanding the processes and mechanisms that control preferential flow in soils in relation to the properties of their structures is still challenging since fast flow and transport occur in a small fraction of the porosity, that is, the functional macropore network, making it difficult to image and characterize these processes at decimeter scales. The aim of the paper was therefore to propose a new image acquisition and analysis methodology to characterize preferential flow at the core scale and identify the resulting active macropore network. Water infiltration was monitored by a sequence of three-dimensional images (taken at 5-, 10-, or 15-min intervals) with an X-ray scanner that allows very fast acquisitions (10 s for a 135-mm diameter). A simultaneous dye tracer experiment was also conducted. Water infiltration was then imaged at each acquisition time by the voxels impacted by water during infiltration, named the water voxels. The number of times a voxel was impacted by water during the experiment was converted into data reflecting the water detection frequency at the given position in the soil column, named the local detection frequency. Compared with dye staining, the active macropore network was defined by macropores in which water voxels were the most frequently detected during the experiment (local detection frequency above 65%). The geometric properties of this active network, such as the connectivity, were significantly different from those of the total structure. This image processing methodology coupled to dynamic acquisitions can be used to improve the analysis of preferential flow processes related to soil structures at the core scale. © Soil Science Society of America.

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