Fundacion Instituto Euromediterraneo del Agua

Villaveza del Agua, Spain

Fundacion Instituto Euromediterraneo del Agua

Villaveza del Agua, Spain
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Baudron P.,Fundacion Instituto Euromediterraneo del Agua | Baudron P.,CIRAD - Agricultural Research for Development | Barbecot F.,GEOTOP UQAM | Barbecot F.,University Paris - Sud | And 6 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.

Baudron P.,Fundacion Instituto Euromediterraneo del Agua | Baudron P.,CIRAD - Agricultural Research for Development | Baudron P.,University Paris - Sud | Barbecot F.,GEOTOP UQAM | And 8 more authors.
Radiocarbon | Year: 2013

Radiocarbon decay is rarely used to assess the residence time of modern groundwater due to the low resolution of its long half-life in comparison to the expected range of ages. Nonetheless, the modern 14C peak induced by the nuclear bomb tests traces efficiently the impacts of recent human activities on groundwater recharge, as well as for tritium. A simple lumped parameter model (LPM) was implemented in order to assess the interest of 14C and 3H nuclear peaks in a highly anthropized aquifer system of southeastern Spain under intense agricultural development. It required i) to assess a correction factor for modern 14C activities and ii) to reconstruct the 3H recharge input function, affected by irrigation. In such a complex hydrogeological context, an exponential model did not provide satisfying results for all samples. A better solution was reached by taking into account the qualitative recent variation of the recharge rates into a combined exponential flow and piston flow model. Apart from presenting an uncommon approach for 14C dating of modern groundwater, this study highlights the need of considering not only the variation of the tracer but also the variability of recharge rates in LPMs. © 2013 by the Arizona Board of Regents on behalf of the University of Arizona.

Baudron P.,Fundacion Instituto Euromediterraneo del Agua | Baudron P.,IRSTEA | Baudron P.,University Paris - Sud | Alonso-Sarria F.,University of Murcia | And 5 more authors.
Journal of Hydrology | Year: 2013

Accurate identification of the origin of groundwater samples is not always possible in complex multilayered aquifers. This poses a major difficulty for a reliable interpretation of geochemical results. The problem is especially severe when the information on the tubewells design is hard to obtain. This paper shows a supervised classification method based on the Random Forest (RF) machine learning technique to identify the layer from where groundwater samples were extracted. The classification rules were based on the major ion composition of the samples. We applied this method to the Campo de Cartagena multi-layer aquifer system, in southeastern Spain. A large amount of hydrogeochemical data was available, but only a limited fraction of the sampled tubewells included a reliable determination of the borehole design and, consequently, of the aquifer layer being exploited. Added difficulty was the very similar compositions of water samples extracted from different aquifer layers. Moreover, not all groundwater samples included the same geochemical variables. Despite of the difficulty of such a background, the Random Forest classification reached accuracies over 90%. These results were much better than the Linear Discriminant Analysis (LDA) and Decision Trees (CART) supervised classification methods. From a total of 1549 samples, 805 proceeded from one unique identified aquifer, 409 proceeded from a possible blend of waters from several aquifers and 335 were of unknown origin. Only 468 of the 805 unique-aquifer samples included all the chemical variables needed to calibrate and validate the models. Finally, 107 of the groundwater samples of unknown origin could be classified. Most unclassified samples did not feature a complete dataset. The uncertainty on the identification of training samples was taken in account to enhance the model. Most of the samples that could not be identified had an incomplete dataset. © 2013 Elsevier B.V.

Baudron P.,Fundacion Instituto Euromediterraneo del Agua | Baudron P.,IRSTEA | Baudron P.,Ecole Polytechnique de Montréal | Baudron P.,General Electric | And 11 more authors.
Journal of Hydrology | Year: 2015

In highly anthropized watersheds, surface water tributaries may carry unexpected high quantities of radon and radium to coastal lagoons. Investigating submarine groundwater discharge (SGD) with radionuclide tracers is therefore a complex task. In order to quantify SGD and decipher the influence of the different water sources, we combined a radon (222Rn) and short-lived radium (223Ra, 224Ra) survey with the hydrodynamic modeling of a lagoon. We applied it to the Mar Menor lagoon (SE Spain) where surface water tributaries and undocumented emissaries carry water from groundwater drainage and brines from groundwater desalinization. We identified the areas of influence of the plume of radionuclides from the river, located major areas of SGD and proposed a location for two submarine emissaries. Porewater, i.e. interstitial water from underlying sediments, was found to be the most representative SGD end member, compared to continental groundwater collected from piezometers. Mass balances in winter and summer seasons provided yearly SGD fluxes of water of 0.4-2.2{dot operator}108m3/y (222Rn), 4.4-19.0{dot operator}108m3/y (224Ra) and 1.3{dot operator}108m3/y (223Ra, measured in winter only). Tidal pumping was identified as a main driver for recirculated saline groundwater, while fresh submarine groundwater discharge from the aquifer ranged between 2% and 23% of total SGD. © 2015 Elsevier B.V.

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