Guillaume Bertrand

Review: From multi-scale conceptualization to a classification system for inland groundwater-dependent ecosystems

Aquifers provide water, nutrients and energy with various patterns for many aquatic and terrestrial ecosystems. Groundwater-dependent ecosystems (GDEs) are increasingly recognized for their ecological and socio-economic values. The current knowledge of the processes governing the ecohydrological functioning of inland GDEs is reviewed, in order to assess the key drivers constraining their viability. These processes occur both at the watershed and emergence scale. Recharge patterns, geomorphology, internal geometry and geochemistry of aquifers control water availability and nutritive status of groundwater. The interface structure between the groundwater system and the biocenoses may modify the groundwater features by physicochemical or biological processes, for which biocenoses need to adapt. Four major types of aquifer-GDE interface have been described: springs, surface waters, peatlands and terrestrial ecosystems. The ecological roles of groundwater are conditioned by morphological characteristics for spring GDEs, by the hyporheic zone structure for surface waters, by the organic soil structure and volume for peatland GDEs, and by water-table fluctuation and surface floods in terrestrial GDEs. Based on these considerations, an ecohydrological classification system for GDEs is proposed and applied to Central and Western-Central Europe, as a basis for modeling approaches for GDEs and as a tool for groundwater and landscape management.RésuméLes aquifères fournissent eau, nutriments et énergie, selon des mécanismes variés, à beaucoup d’écosystèmes aquatiques et terrestres. Les écosystèmes dépendant des eaux souterraines (EDES) sont de plus en plus reconnus pour leur valeur écologique et socio-économique. Les connaissances actuelles sur les processus contrôlant le fonctionnement éco-hydrologique des EDES continentaux sont passées en revue, de façon à identifier les facteurs-clés qui conditionnent leur viabilité. Ces processus ont lieu à la fois à l’échelle du bassin versant et de l’émergence. Les types de recharge, la géomorphologie, la structure et la géochimie des aquifères contrôlent la disponibilité en eau nutritive des nappes. La structure de l’interface système souterrain-biocénoses peut modifier les caractéristiques des nappes du fait des processus physico-chimiques et biologiques, auxquels les biocénoses doivent s’adapter. Quatre types majeurs d’interface aquifère-EDES sont décrits : sources, eaux de surface, tourbières et écosystèmes terrestres. Le rôle écologique des eaux souterraines est conditionné par les caractéristiques morphologiques pour l’interface sources-EDES, par la structure de la zone hyporhéïque pour les eaux de surface, par la structure et le volume du sol organique pour l’interface tourbières-EDES et par la fluctuation de la surface libre et par les écoulements de surface dans les EDES terrestres. Sur la base de ces considérations, un système de classification éco-hydrologique pour les EDES est proposé et appliqué à l’Europe du Centre et du Centre-Ouest, comme fondement pour des modélisation des EDES et comme outil de gestion des eaux souterraines et des paysages.ResumenLos acuíferos proporcionan agua, nutrientes y energía con varios esquemas para muchos ecosistemas acuáticos y terrestres. Los ecosistemas dependientes del agua subterránea (GDEs) son cada vez más reconocidos por sus valores ecológicos y socioeconómicos. Se realiza una revisión del conocimiento actual de los procesos que gobiernan el funcionamiento ecohidrológico de los GDEs interiores, para evaluar los principales factores que limitan su viabilidad. Estos procesos ocurren tanto en escala de cuenca como de la emergencia. Los esquemas de la recarga, la geomorfología, la geometría interna y la geoquímica de los acuíferos controlan la disponibilidad del agua y el estado de los nutrientes del agua subterránea. La estructura de interfaz entre el sistema de agua subterránea y la biocenosis pueden modificar las características del agua subterránea por procesos fisicoquímicos y biológicos, para los cuales la biocenosis necesita adaptarse. Cuatro tipos principales de la interfaz de acuíferos GDEF han sido descriptos: manantiales, aguas superficiales, turberas y ecosistemas terrestres. Los roles ecológicos del agua subterránea están condicionados por las características morfológicas para los manantiales GDEs, por la estructura de la zona hiporreica para las aguas superficiales, por la estructura orgánica del suelo y por el volumen de los GDEs con turberas, y por la fluctuación de los niveles freáticos y las inundaciones de superficie en los GDEs terrestres. Basado en estas consideraciones se propone un sistema de clasificación ecohidrológico para los GDEs y es aplicado para el centro – oeste y el centro de Europa., como una base para modelar enfoques para los GDEs y como una herramienta para el manejo del agua subterránea y el paisaje.摘要含水层能够为许多水生和陆地生态系统提供水以及各种类型的营养和能量。依赖地下水的生态系统(GDEs)的生态及社会经济价值越来越被认可。本文综述了控制内陆GDEs生态水文功能的过程研究现状,从而评价限制其发展的主要驱动力。这些过程发生在流域及更大尺度上。含水层的补给类型、地形地貌、内部几何形状以及地球化学控制着水资源可利用量和地下水的营养状况。地下水系统及生物群落之间的界面结构可通过物理化学和生物过程改变地下水特征,并需要生物群落的适应。本文对四个主要类型的含水层—GDE界面进行描述;泉、地表水、沼泽、陆地生态系统。地下水的生态作用由形态学特征约束,对泉水GDEs而言,由伏流区结构约束,对地表水,由有机土壤结构和体积约束,对沼泽GDEs,由地下水位波动约束,对陆地GDEs由地表洪水约束。基于这些因素,本文提出一个GDEs生态水文分类系统,并应用到欧洲中部和中西部,从而为建立GDEs模型打下基础,为地下水及景观管理提供工具。ResumoOs aquíferos fornecem água, nutrientes e energia com vários padrões para muitos ecossistemas aquáticos e terrestres. Os ecossistemas dependentes das águas subterrâneas (EDAS) são crescentemente reconhecidos pelos seus valores ecológicos e socioeconómicos. Revê-se o conhecimento actual dos processos que determinam o funcionamento eco-hidrológico dos EDAS interiores de forma a avaliar os factores principais que condicionam a sua viabilidade. Estes processos ocorrem tanto à escala da bacia hidrográfica como à escala da emergência. Os padrões de recarga, geomorfologia, geometria interna e geoquímica dos aquíferos controlam a disponibilidade de água e o estado nutritivo das águas subterrâneas. A estrutura da interface entre o sistema de águas subterrâneas e as biocenoses pode modificar as características das águas subterrâneas por processos físico-químicos ou biológicos para os quais as biocenoses precisam de se adaptar. Descreveram-se quatro tipos principais de interface aquífero-EDAS: nascentes, águas superficiais, turfeiras e ecossistemas terrestres. O papel ecológico das águas subterrâneas está condicionado pelas características morfológicas no caso dos EDAS associados a nascentes, pela estrutura da zona hiporreica para as águas superficiais, pela estrutura e volume do solo orgânico no caso dos EDAS associados a turfeiras e pela flutuação do nível freático e das cheias de águas superficiais no caso dos EDAS terrestres. Com base nestas considerações, propõe-se um sistema de classificação ecohidrológica para os EDAS e faz-se a sua aplicação à Europa Central e Centro-ocidental como uma base para as abordagens de modelação de EDAS e como uma ferramenta para a gestão das águas subterrâneas e da paisagem.

Origins and processes of groundwater salinization in the urban coastal aquifers of Recife (Pernambuco, Brazil): A multi-isotope approach

In the coastal multilayer aquifer system of a highly urbanized southern city (Recife, Brazil), where groundwaters are affected by salinization, a multi-isotope approach (Sr, B, O, H) was used to investigate the sources and processes of salinization. The high diversity of the geological bodies, built since the Atlantic opening during the Cretaceous, highly constrains the heterogeneity of the groundwater chemistry, e.g. Sr isotope ratios, and needs to be integrated to explain the salinization processes and groundwater pathways. A paleoseawater intrusion, most probably the 120 kyB.P. Pleistocene marine transgression, and cationic exchange are clearly evidenced in the most salinized parts of the Cabo and Beberibe aquifers. All (87)Sr/(86)Sr values are above the past and present-day seawater signatures, meaning that the Sr isotopic signature is altered due to additional Sr inputs from dilution with different freshwaters, and water-rock interactions. Only the Cabo aquifer presents a well-delimitated area of Na-HCO3 water typical of a freshening process. The two deep aquifers also display a broad range of B concentrations and B isotope ratios with values among the highest known to date (63-68.5‰). This suggests multiple sources and processes affecting B behavior, among which mixing with saline water, B sorption on clays and mixing with wastewater. The highly fractionated B isotopic values were explained by infiltration of relatively salty water with B interacting with clays, pointing out the major role played by (palaeo)-channels for the deep Beberibe aquifer recharge. Based on an increase of salinity at the end of the dry season, a present-day seawater intrusion is identified in the surficial Boa Viagem aquifer. Our conceptual model presents a comprehensive understanding of the major groundwater salinization pathways and processes, and should be of benefit for other southern Atlantic coastal aquifers to better address groundwater management issues.

Environmental tracers and indicators bringing together groundwater, surface water and groundwater-dependent ecosystems: importance of scale in choosing relevant tools

Groundwater–surface water (GW–SW) interactions cover a broad range of hydrogeological and biological processes and are controlled by natural and anthropogenic factors at various spatio-temporal scales, from watershed to hyporheic/hypolentic zone. Understanding these processes is vital in the protection of groundwater-dependent ecosystems increasingly required in water resources legislation across the world. The use of environmental tracers and indicators that are relevant simultaneously for groundwater, surface water and biocenoses–biotope interactions constitutes a powerful tool to succeed in the management task. However, tracer type must be chosen according to the scale of interest and tracer use thus requires a good conceptual understanding of the processes to be evaluated. This paper reviews various GW–SW interaction processes and their drivers and, based on available knowledge, systemises application of conservative tracers and semi-conservative and reactive environmental indicators at different spatial scales. Biocenoses–biotopes relationships are viewed as a possible transition tool between scales. Relation between principal application of the environmental tracers and indicators, examples and guidelines are further proposed for examining GW–SW interactions from a hydrogeological and biological point of view by demonstrating the usability of the tracers/indicators and providing recommendations for the scientific community and decision makers.

Evaluation of pharmaceuticals in surface water: Reliability of PECs compared to MECs

Due to the current analytical processes that are not able to measure all the pharmaceutical molecules and to the high costs and the consumption of time to sample and analyze PhACs, models to calculate Predicted Environmental Concentrations (PECs) have been developed. However a comparison between MECs and PECs, taking into account the methods of calculations and peculiarly the parameters included in the calculation (consumption data, pharmacokinetic parameters, elimination rate in STPs and in the environment), is necessary to assess the validity of PECs. MEC variations of sixteen target PhACs [acetaminophen (ACE), amlodipine (AML), atenolol (ATE), caffeine (CAF), carbamazepine (CAR), doxycycline (DOX), epoxycarbamazepine (EPO), fluvoxamine (FLU), furosemide (FUR), hydrochlorothiazide (HYD), ifosfamide (IFO), losartan (LOS), pravastatin (PRA), progesterone (PROG), ramipril (RAM), trimetazidine (TRI)] have been evaluated during one hydrological cycle, from October 2011 to October 2012 and compared to PECs calculated by using an adaptation of the models proposed by Heberer and Feldmann (2005) and EMEA (2006). Comparison of PECs and MECS has been achieved for six molecules: ATE, CAR, DOX, FUR, HYD and PRA. DOX, FUR and HYD present differences between PECs and MECs on an annual basis but their temporal evolutions follow the same trends. PEC evaluation for these PhACs could then be possible but need some adjustments of consumption patterns, pharmacokinetic parameters and/or mechanisms of (bio)degradation. ATE, CAR and PRA are well modeled; PECs can then be used as reliable estimation of concentrations without any reserve.

Glacial recharge, salinisation and anthropogenic contamination in the coastal aquifers of Recife (Brazil)

Implying large residence times and complex water origins deep coastal aquifers are of particular interest as they are remarkable markers of climate, water use and land use changes. Over the last decades, the Metropolitan Region of Recife (Brazil) went through extensive environmental changes increasing the pressure on water resources and giving rise to numerous environmental consequences on the coastal groundwater systems. We analysed the groundwater of the deep aquifers Cabo and Beberibe that are increasingly exploited. The processes potentially affecting groundwater residence times and flow paths have been studied using a multi-tracer approach (CFCs, SF6, noble gases, 14C, 2H and 18O). The main findings of these investigations show that: (1) Groundwaters of the Cabo and Beberibe aquifers have long residence times and were recharged about 20,000years ago. (2) Within these old groundwaters we can find palaeo-climate evidences from the last glacial period at the tropics with lower temperatures and dryer conditions than the present climate. (3) Recently, the natural slow dynamic of these groundwater systems was significantly affected by mixing processes with contaminated modern groundwater coming from the shallow unconfined Boa Viagem aquifer. (4) The large exploitation of these aquifers leads to a modification of the flow directions and causes the intrusion through palaeo-channels of saline water probably coming from the Capibaribe River and from the last transgression episodes. These observations indicate that the current exploitation of the Cabo and Beberibe aquifers is unsustainable regarding the long renewal times of these groundwater systems as well as their ongoing contamination and salinisation. The groundwater cycle being much slower than the human development rhythm, it is essential to integrate the magnitude and rapidity of anthropogenic impacts on this extremely slow cycle to the water management concepts.

Groundwater contamination in coastal urban areas: Anthropogenic pressure and natural attenuation processes. Example of Recife (PE State, NE Brazil)

In a context of increasing land use pressure (over-exploitation, surface-water contamination) and repeated droughts, identifying the processes affecting groundwater quality in coastal megacities of the tropical and arid countries will condition their long-term social and environmental sustainability. The present study focuses on the Brazilian Recife Metropolitan Region (RMR), which is a highly urbanized area (3,743,854 inhabitants in 2010) on the Atlantic coast located next to an estuarial zone and overlying a multi-layered sedimentary system featured by a variable sediment texture and organic content. It investigates the contamination and redox status patterns conditioning potential attenuation within the shallow aquifers that constitute the interface between the city and the strategic deeper semi-confined aquifers. These latter are increasingly exploited, leading to high drawdown in potenciometric levels of 20-30m and up to 70m in some high well density places, and potentially connected to the surface through leakage. From a multi-tracer approach (major ions, major gases, δ(11)B, δ(18)O-SO4, δ(34)S-SO4) carried out during two field campaigns in September 2012 and March 2013 (sampling of 19 wells and 3 surface waters), it has been possible to assess the contamination sources and the redox processes. The increasing trend for mineralization from inland to coastal and estuarial wells (from 119 to around 10,000μS/cm) is at first attributed to water-rock interactions combined with natural and human-induced potentiometric gradients. Secondly, along with this trend, one finds an environmental pressure gradient related to sewage and/or surface-channel network impacts (typically depleted δ(11)B within the range of 10-15‰) that are purveyors of chloride, nitrate, ammonium and sulfate. Nitrate, ammonium and sulfate (ranging from 0 to 1.70mmol/L, from 0 to 0,65mmol/L, from 0.03 to 3.91mmol/L respectively are also potentially produced or consumed through various redox processes (pyrite oxidation, denitrification, dissimilatory nitrate reduction to ammonium) within the system, as is apparent within a patchwork of biogeochemical reactors. Furthermore, intensive pumping in the coastal area with its high well density punctually leads to temporary well salinization ([Cl] reaching temporarily 79mmol/L). Our results, summarized as a conceptual scheme based on environmental conditions, is a suitable basis for implementing sustainable management in coastal sedimentary hydrosystems influenced by highly urbanized conditions.

Multi-layered water resources, management, and uses under the impacts of global changes in a southern coastal metropolis: When will it be already too late? Crossed analysis in Recife, NE Brazil

Coastal water resources are a worldwide key socio-environmental issue considering the increasing concentration of population in these areas. Here, we propose an integrative transdisciplinary approach of water resource, water management and water access in Recife (NE Brazil). The present-day water situation is conceptualized as an imbricated multi-layered system: a multi-layered water resource, managed by a multi-layered governance system and used by a multi-layered social population. This allows identifying processes of quantitative, qualitative, and sanitary conflicts between governance and population strategies regarding water supply, as well as the institutional and individual denials of these conflicts. Based on this model, we anticipate future water-related problematic fates. Concerning the water resource system, the rapid groundwater level decrease due to unsustainable water predatory strategies, and the very low recharge rate have drastically modified the aquifer system functioning, inducing hydraulic connection between shallow groundwater (contaminated and locally salty) and deep ones (mostly fresh, with local inherited salinity), threatening the deep strategic water resource. Concerning the water governance system, the investments to increase the capacity storage of surface water, the water regulation agencies and the public/private partnership should shortly improve the water supply and wastewater issue. Nevertheless, the water situation will remain highly fragile due to the expected water demand increase, the precipitation decrease and the sea-level increase. Concerning the water access system, the population variably perceives these current and further effects and the possible mitigation policies, and develops alternative individual strategies. Authorities, policymakers and water managers will have to implement a well-balanced water governance, taking into account the specificities of the PPP, public and private groundwater users, and with a strong political willingness for a sustainable water management to ensure water supply for all the population. In other words, an anticipatory and integrated vision is necessary to reduce the discrepancies in this complex system.

Contaminant transfer and hydrodispersive parameters in basaltic lava flows: artificial tracer test and implications for long-term management

Abstract The aim of this paper is to evaluate the vulnerability after point source contamination and characterize water circulations in volcanic flows located in the Argnat basin volcanic system (Chaîne des Puys, French Massif Central) using a tracer test performed by injecting a iodide solution. The analysis of breakthrough curves allowed the hydrodispersive characteristics of the massive lava flows to be determined. Large Peclet numbers indicated a dominant advective transport. The multimodal feature of breakthrough curves combined with high values of mean velocity and low longitudinal dispersion coefficients indicated thatwater flows in an environment analogous to a fissure system, and only slightly interacts with a low porosity matrix (ne < 1%). Combining this information with lava flow stratigraphy provided by several drillings allowed a conceptual scheme of potential contaminant behaviour to be designed. Although lava flows are vulnerable to point source pollution due to the rapid transfer of water within fractures, the saturated scoriaceous layers located between massive rocks should suffice to strongly buffer the transit of pollution through dilution and longer transit times. This was consistent with the low recovery rate of the presented tracer test.