Characterising rainfall regimes in relation to recharge of the Sierra de Gador-Campo de Dalias aquifer system (S-E Spain)

This paper demonstrates the use of the deuterium excess parameter to distinguish between origin of precipitation in the Mediterranean basin. Isotope signatures in precipitation from the GNIP network around the Mediterranean basin and literature data are combined with isotopic data from aquifers in south east Spain to explain the typology of the precipitation events dominating recharge. Although precipitation from Atlantic origin (d-excess = 10‰) occurs more frequently in the western Mediterranean basin, the quantities in each event are generally moderate to low. Important rainfall events generally have Mediterranean origin (d-excess=15‰). The total precipitation in Gibraltar is a mixture between precipitation from both origins (d-excess in Gibraltar = 12.39‰). However, with increasing volume of the storms the Mediterranean character dominates. These heavier storms contribute mainly to recharge, as illustrated by the d-excess of 13.8‰ in deep groundwater of the Campo de Dalias (Almeria province). One of the challenges to meet ever-growing water demands is to increase recharge from events with a low return period yielding intermediate quantities per event, but forming the bulk of the annual precipitation.Cet article met en avant le paramètre «excès en deutérium» dans la détermination de l’origine des précipitations dans le bassin méditerranéen. Afin d’expliquer la nature des précipitations qui dominent la recharge de l’aquifère, nous avons combiné les signatures isotopiques fournies par le réseau GNIP avec les données de la littérature ainsi que des teneurs isotopiques provenant d’aquifères du sud-est de l’Espagne. Dans la partie ouest du bassin méditerranéen les précipitations provenant de l’Atlantique (excès en d. = 10‰) sont fréquentes mais celles d’origine méditerranéenne (excès en d. = 15‰) possèdent des volumes mensuels plus importants. La teneur isotopique des précipitations totales à Gibraltar indique une origine géographique mixte des pluies (excès en d. à Gibraltar = 12,39 ‰). Plus les volumes mensuels de pluie sont élevés plus le caractère méditerranéen s’affirme. Ces fortes précipitations contribuent principalement à la recharge, en effet l’excès en deutérium des nappes profondes du Campo de Dalias (province d’Almeria) correspond à 13,8 ‰. L’un des défis rencontrés pour satisfaire la demande croissante d’eau consiste à accroître la recharge à partir de précipitations présentant une faible période de retour et produisant des quantités moyennes de pluie par événement, mais qui constituent la majeure partie des précipitations annuelles

Caracterisation des precipitations en fonction de la recharge de l'aquifere de Sierra de Gador-Campo de dalias (S.E. Espagne)

This paper demonstrates the use of the deuterium excess parameter to distinguish between origin of precipitation in the Mediterranean basin. Isotope signatures in precipitation from the GNIP network around the Mediterranean basin and literature data are combined with isotopic data from aquifers in south east Spain to explain the typology of the precipitation events dominating recharge. Although precipitation from Atlantic origin (d-excess = 10‰) occurs more frequently in the western Mediterranean basin, the quantities in each event are generally moderate to low. Important rainfall events generally have Mediterranean origin (d-excess= 15‰). The total precipitation in Gibraltar is a mixture between precipitation from both origins (d-excess in Gibraltar = 12.39‰). However, with increasing volume of the storms the Mediterranean character dominates. These heavier storms contribute mainly to recharge, as illustrated by the d-excess of 13.8‰ in deep groundwater of the Campo de Dalias (Almeria province). One of the challenges to meet ever-growing water demands is to increase recharge from events with a low return period yielding intermediate quantities per event, but forming the bulk of the annual precipitation.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Characterising rainfall regimes in relation to recharge of the Sierra de Gador-Campo de Dalias aquifer system

info:eu-repo/semantics/publishe

Choix de pratique culturale en présence d'incitations à la réduction des émissions d'herbicides : une simulation en milieu viticole méditerranéen

Science updateNational audiencePour analyser l'impact de diverses mesures d'orientation de la viticulture méridionale sur la qualité des eaux à l'exutoire d'un bassin versant viticole, un modèle couplé hydrologique et agro-économique est proposé. Le document explore les conséquences, en terme d'émission d'herbicide, de divers schémas incitatifs. Affectant les inputs (taxation) ou les outputs (bonification et pénalisation de cépages déterminés), les instruments incitatifs modifient les quantités de polluants émises et la répartition spatiale des émissions, l'amplitude et la localisation des émissions intervenant dans le mécanisme décrit par les équations du modèle hydrologique. L'analyse de l'impact des schémas incitatifs repose sur la programmation multiparamétrique. Les résultats importants concernent le caractère fortement non linéaire de la réponse des viticulteurs aux incitants proposés et l'inadéquation d'instruments généralistes lorsqu'un site bien délimité est ciblé

Gérer la pollution par les herbicides: une simulation en milieu viticole méditerranéen. L'émission de polluants vue comme problème de décision

[eng] Regulation of herbicide pollution in vineyard: a simulation in a mediterranean area - We investigate in a hydrologic-economic integrated model framework, how different incentive instruments aiming at regulating the emission of no-point source pollutants (herbicides) do heva an impact on cultural practices. Based on multiparametric programming techniques, two combined tools are considered by the decision model: (i) positive and negative quality-based differentiation of the price of the products and (ii) positive differentiation and tax on the polluting inputs. Non-linear responses are observed, with a favorable environmental effect at the farm level when positive différenciation of the price is noticeable. However, this favorable response at the farm level results into poor performances at the watershed level, because the described incentive design does not include location-based devices. [fre] Cet article expose une approche des possibilités de gestion des pollutions par herbicides en milieu viticole méditerranéen à l'aide des outils de la programmation multiparamétrique. Deux hypothèses de politique de limitation de la pollution sont proposées, par bonification et pénalisation des produits et en associant une taxation des intrants et une bonification des produits. Les résultats montrent que, séparément, bonification et taxation ont un effet environnemental favorable. Leur combinaison entraîne des réponses profondément nonlinéaires pouvant conduire, localement, à des résultats environnementaux contreproductifs. De plus, l'effet positif au niveau de l'exploitation correspond à de médiocres performances sur le Bassin versant proprement dit, les mesures envisagées par les scénarios n'étant pas localisées.

Temporal dynamics of bio-available Si fluxes in a temperate forested catchment (Meerdaal forest, Belgium)

Silicon (Si) is a key element in global biogeochemical cycling and recent research has shown that changes in the biological component of the Si cycle may lead to more rapid variations in the land–ocean Si transfer than previously thought. The objective of this paper is to better understand the controls on temporal Si dynamics in terrestrial ecosystems, by studying Si fluxes from a small forested catchment in central Belgium. An intensive monitoring program (2008–2010) of dissolved and amorphous silica (DSi and ASi) concentrations and load patterns show that DSi concentrations are significantly lower during winter–spring periods than during summer–autumn periods. In contrast to what was found in other studies, seasonal dynamics in Meerdaal forest are not controlled by variations in biological uptake or temperature, but mainly by the more important supply of pore-water to the groundwater table in winter–spring periods. Analysis of seasonal and event fluctuations in stream water DSi concentrations showed that final stream water is a mixture of old, DSi rich water pushed out of the soil, and new, DSi poor water delivered by quick flow. The mixing of old and new water finally resulted in streamwater DSi concentrations responding only moderately to variations in discharge (near-chemostatic behaviour). We estimated the total DSi export from the system to be ca. 65.1 9 103 mol km-2 year-1. Because Si delivery is biologically regulated through an important Si cycle in the vegetation-soil continuum, an anthropogenic (e.g. agricultural expansion) or climatic disturbance of terrestrial ecosystems may alter both water residence times through shifts in hydrological regimes and the DSi chemical equilibrium concentration in soils. In turn, these perturbations will potentially alter long-term DSi and ASi inputs to aquatic systems

A trade-off between dissolved and amorphous silica transport during peak-flow events (Scheldt river basin, Belgium) : impacts of precipitation intensity on terrestrial Si dynamics in strongly cultivated catchments

Amorphous, biogenic Si (ASi) is stored in large amounts in terrestrial ecosystems. The study of terrestrial ASi mobilization remains in the pioneer research stage: most Si budget studies have not included the biogenic amorphous Si stock and fluxes. This hampers our ability to accurately quantify terrestrial mobilization of Si, which is—through ocean carbon burial and CO2 uptake during terrestrial Si weathering—intricately linked to global carbon budgets. We studied detailed concentration and load patterns of dissolved (DSi) and ASi during several high-discharge events in eight first-order river basins. Based on high frequency discharge measurements and concurrent analysis of ASi and DSi concentrations at base flow and during intense precipitation events, we were able to attribute a percentage of yearly ASi and DSi fluxes to both base flow and precipitation event related surface run-off. Our results show ASi and DSi concentrations in upstream river basins to be intricately linked to each other and to discharge, and ASi transport constitutes an important part to the total transport of Si even through first-order river basins (up to 40%). Based on our observations, increased occurrence of peak-discharge events with global climatic changes, and lowered importance of base flow, will coincide with drastic changes in ASi and DSi dynamics in the river continuum. Our work clearly shows ASi dynamics should be incorporated in global Si budgets now, even in low-order small river basin