AQUI-FR

by | Aug 25, 2022

AQUI-FR

national hydrogeological modeling platform (France)

AQUI-FR

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People in charge of the innovative practice :

Jean-Pierre VERGNES – jp.vergnes@brgm.fr

AQUI-FR is a national hydrogeological modeling platform designed as a tool to valorize hydrogeological modeling work done in France. Started in 2014, AQUI-FR aims to bring together within a single digital platform hydrogeological models developed by different research institutes. AQUI-FR thus brings together 8 partners (ENS, CERFACS, BRGM, Ecole des Mines PARIS, Météo France, Géosciences Rennes, LHyges, UMR METIS) with the aim of developing a better knowledge of past, present, and future groundwater resources. AQUI-FR aims to implement forecasts of groundwater evolution in France, on time scales ranging from days to seasons (+6 months), and from atmospheric forecasts via standardized piezometric indicators. The platform also allows to carry out prospective modelling (up to 2100), based on hydrogeological modelling developed and used by water managers when they exist, and to promote the development of these modelling when they do not. A computer structure allows the association of 3 hydrogeological models (EROS, MARTHE, EauDyssée), a water and energy flow model (SURFEX), and an atmospheric analysis system (SAFRAN). The dynamic coupling of the models is provided by the OpenPALM coupler. The AQUI-FR platform is deployed on the operational machines of Météo-France and benefits from its support for daily monitoring. The platform has been used on a total of 14 distributed aquifer applications and 23 applications on karst systems. In the future, other regional models will be integrated to extend the spatial coverage.

Figure 1 : Concept of the AQUI-FR platform.

Responsible entity

Several entities are responsible for the AQUI-FR platform. The Geoscience department of the ENS is the coordinator of the platform.

Institutional setting

As the national model is built on existing hydrogeological applications, each partner remains the owner of its hydrogeological model and the results are available to the general public.

Geographical setting

The simulations from the platform cover 35% of metropolitan France. The EauDyssée model covers Basse-Normandie, Somme, Seine, Loire and four sub-systems: Marne-Loing, Marne-Oise, Seine-Eure, Seine-Oise. The MARTHE model covers Alsace, Basse-Normandie, Nord Pas-de-Calais, Poitou-Charentes, and Somme. Finally, the EROS model covers 23 karst systems (median size 99 km²).

Detailed explanation

The modeling platform represents the main hydrological processes occurring in watersheds, from precipitation to groundwater flow. In its current form, the AQUI-FR system includes three hydrogeological modeling software covering 11 sedimentary aquifers and 23 karst systems: the hydrogeological numerical platform EauDyssée, the MARTHE software and the EROS software used for karst systems. The three software are embedded in an application developed with the OpenPALM coupling syste.

All these models cover an area of about 149,000 km2 and contain up to 10 superimposed aquifer layers. AQUI-FR takes into account spatial heterogeneity by using different spatial scales. The SAFRAN meteorological analysis available over the French metropolitan area at a resolution of 8 km provides meteorological variables to the SURFEX land surface model that evaluates the water balance over the French metropolitan area. SAFRAN provides hourly precipitation (rain and snow), temperature, relative air humidity, wind speed and downward radiation. SURFEX uses these atmospheric variables to solve the surface energy and water balance at the land-atmosphere interface at a scale of 1-2 years and a time step of 5 minutes. SURFEX estimates the spatial distribution of flux between surface runoff and groundwater recharge on the SAFRAN. It accounts for different soil and vegetation types and uses a diffusion scheme to represent heat and water transfer through the soil. The soil in SURFEX is represented by a multilayer approach. Its depth varies according to the vegetation (in France from 0.2 to 3 m) and is partially accessible to plant roots. The infiltration of the soil at depth constitutes the recharge flow of the water table. Surface runoff can occur as a function of excess saturation or excess infiltration. The simulation of the watershed depends on its hydrogeological characteristics. For sedimentary basins, these two flows are transferred to the groundwater models MARTHE or EauDyssée. These models simulate transfer to the unsaturated zone, groundwater flows within and between aquifers, runoff to and in rivers, and river-aquifer exchanges. They also take into account the numerous groundwater withdrawals from river basins. The temporal resolution is daily, and the spatial resolution varies from 100 m to a maximum of 8,000 m. The depth of the deepest aquifer can locally reach about 1,000 m. It should be noted that the hydrogeological models could have been conventionally fed with precipitation, potential evapotranspiration, and temperature data from the SAFRAN analysis using their own water balance calculations. However, the combined use of SURFEX and SAFRAN provides a consistent set of hydro-meteorological data on an 8 km resolution grid over France, including groundwater recharge and surface runoff from SURFEX, as well as potential evapotranspiration, precipitation and temperature from SAFRAN. The use of these 8 km resolution flows from SURFEX necessitated recalibration of the hydrogeological models included in the platform. Karst aquifer systems are simulated by a conceptual reservoir modeling approach using EROS software. Each karst system is represented by a reservoir model at a daily time scale. Conceptual approaches are preferred for the simulation of karst systems. Indeed, their heterogeneities make it difficult to use a physics-based approach. EROS uses daily precipitation, snow, temperature and potential evapotranspiration provided by SAFRAN to calculate karst spring flows. Technically, the AQUI-FR hydrogeological modeling platform was developed using the OpenPALM coupling system, which allows easy integration of high-performance computing applications in a flexible and scalable manner. In the OpenPALM framework, applications are divided into elementary components that can exchange data. The AQUI-FR platform is an OpenPALM application that currently includes five components.

A preliminary step is performed to estimate groundwater recharge and surface runoff with SURFEX taking into account SAFRAN atmospheric forcing before launching OpenPALM. This preliminary step gives access to 60 years of daily groundwater recharge and runoff at a regular resolution of 8 km over the entire metropolitan area.

Historical overview

The objectives of the first phase (since 2014) was to show the feasibility of such a tool via the construction of the AQUI-FR computer structure and the first evaluations, as well as to ensure the legal possibilities of exploiting hydrogeological applications in operational, and finally, to identify the elements of interest for the water managers. The construction of the AQUI-FR structure required several steps: (i) to gather the hydrogeological models on the same computer structure that can be mobilized in operational use, (ii) to integrate the different hydrogeological applications available, (iii) to converge towards a homogeneous treatment on a national scale, via at least the use of a common atmospheric forcing, (iv) to recalibrate the applications to make them more compatible with this new forcing.
This work was accompanied by an effort to process the input and output data. An important aspect of the input data is the integration of groundwater withdrawals over the simulated periods, which are difficult to acquire over long periods and for recent periods (2-year delay). The management of output variables requires specific work, taking into account the variables of interest for managers (variable, depth or geological layer, estimation period, estimation domain) and numerical constraints (disk volumes, calculation time). In parallel, two development efforts were carried out, in order to: (i) include a representation of the basement aquifers, with numerical experiments carried out on the Brittany aquifers, and (ii) to allow a correction of the initial states of the aquifers by integrating the available piezometric data.

Evidence of benefits from implementation

The results of the AQUI-FR project confirm the feasibility of bringing together independent hydrogeological models developed in different research institutes in the same coupling platform. All these models were initially developed and calibrated over shorter periods with heterogeneous geological and meteorological databases, but the evaluation of the long-term simulations that has been carried out shows a good comparison with the observations available for the same period. It confirms the relevance of using the AQUI-FR as a tool for long-term impact studies.

Figure 3 : Standardized piezometric level index between observed (a) and simulated (b) piezometers.

The other advantage of this platform is in its modularity. The AQUI-FR platform encourages the development of groundwater modeling where it is lacking and, more generally, it has the potential to be a valuable tool for many applications in water resources management and in water quality studies. research, for example in climate change studies and seasonal forecasts

Replication potential in SUDOE region

The trigger for implementing the practice was the publication of the Explore 2070 project results, which showed a disparate analysis, and thus the idea emerged to harmonize the modeling results to make forecasts. From a technical point of view, few obstacles were encountered. The obstacles encountered were in relation to intellectual property. Indeed, it was necessary to reach an agreement on the sharing of the source code of the Marthe model to implement it on the Météo France platform. On the conceptual side, the models were not perfectly calibrated: some model outputs overlap. From an administrative point of view, it was necessary to convince the regions, because the hydrogeological models were developed within the regional entities of BRGM. Finally, from a functional point of view, the maintenance of the platform requires a permanent researcher per partner. The project was also able to benefit from subsidies (about 100 k€ / year).

Future outlook

In terms of evolution, the project offers several perspectives in terms of: (i) improvement of physical processes: better integration of basement and karst aquifers, and (ii) development: evolution of numerical codes and techniques.

This project also offers prospects for development outside of France, in the French overseas departments and territories, but also prospects within the framework of PEPR (One Water program).

In the future, other regional models will be included to extend the coverage of AQUI-FR (bedrock aquifers located in Brittany). A new modeling method based on a rainfall-runoff model will be used to provide upstream river flows as boundary conditions for the MARTHE models that require it. Finally, since errors in the initial conditions can significantly alter the skill of the forecast, studies dedicated to data assimilation to improve the initial state conditions are also performed in parallel.

Key points of the innovative method

> Multi-model numerical platform
> Daily to seasonal forecasts
> Prospective modeling (up to 2100)

Acknowledgements

The innovative practice was suggested by Jean-Pierre VERGNES (BRGM) who also participated in the interview.

References

Duchaine, F., Jauré, S., Poitou, D., Quémerais, E., Staffelbach, G., Morel, T., and Gicquel, L. (2015). Analysis of high performance conjugate heat transfer with the OpenPALM coupler, Comput. Sci. Discov., 8, 015003, https://doi.org/10.1088/17494699/8/1/015003, 2015.

Habets, F., Amraoui, N., Caballero, Y., Thiéry, D., Vergnes, J-P., Morel, T., Le Moigne, P., Roux, N., de Dreuzy, J-R., Longuevergne, L., Ackerer, P., Maina, F., Besson, F., Etchevers, P., Regimbeau, F., Viennot, P. (2017). Plate-forme de modélisation hydrogéologiques nationale AQUI-FR. Rapport final de 1ère phase 2014-2016. http://www.geosciences.ens.fr/wp-content/uploads/2019/07/Rapport_fin_phase1_Aqui-FR_VF.pdf

Habets, F., Amraoui, N., Caballero, Y., Thiéry, D., Vergnes, J-P., Morel, T., Le Moigne, P., Leroux, D., Roux, N., Courtois, Q., de Dreuzy, J-R., Ackerer, P., Besson, F., Etchevers, P., Regimbeau, F., Vincendon, B., Gallois, N., Viennot, P. (2018). Evolution de la ressource en eau souterraine passée, présente et future estimée par AQUI-FR. Rapport d’étape. http://www.geosciences.ens.fr/wp-content/uploads/2019/07/rapport_d_etape_AquiFR_Juil_2018.pdf

Masson, V., Le Moigne, P., Martin, E., Faroux, S., Alias, A., Alkama, R., Belamari, S., Barbu, A., Boone, A., Bouyssel, F., Brousseau, P., Brun, E., Calvet, J.-C., Carrer, D., Decharme, B., Delire, C., Donier, S., Essaouini, K., Gibelin, A.-L., Giordani, H., Habets, F., Jidane, M., Kerdraon, G., Kourzeneva, E., Lafaysse, M., Lafont, S., Lebeaupin Brossier, C., Lemonsu, A., Mahfouf, J.-F., Marguinaud, P., Mokhtari, M., Morin, S., Pigeon, G., Sal gado, R., Seity, Y., Taillefer, F., Tanguy, G., Tulet, P., Vincendon, B., Vionnet, V., and Voldoire, A. (2013). The SURFEXv7.2 land and ocean surface platform for coupled or offline simulation of earth surface variables and fluxes, Geosci. Model Dev., 6, 929–960, https://doi.org/10.5194/gmd-6-929-2013

Thiéry, D. (2015a). Code de calcul MARTHE – Modélisation 3D des écoulements dans les hydrosystèmes – Notice d’utilisation de la version 7.5 (MARTHE: Modeling software for groundwater flows), BRGM/RP-64554-FR, BRGM, Orléans.

Thiéry, D. (2018a). Logiciel ÉROS version 7.1 – Guide d’utilisation, Rapport final, BRGM/RP-67704-FR, BRGM, Orléans.

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Description and objectives of the project

The scientific community recommends a substantial improvement in the knowledge of aquifers, the establishment of reliable monitoring networks and a greater involvement of the administration and users to achieve a sustainable management of aquifers. The main objective...

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Success stories in groundwater management

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Sustain-COAST

by | Aug 24, 2022

Sustain-COAST

Sustainable management of coastal groundwater and pollution reduction through innovative governance in a context of climate change

Sustain-COAST

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People in charge of the innovative practice :

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SUstain-COAST is a research project co-funded under the PRIMA 2018 section II program, for a period of 3 years from June 2019. The consortium is led by the Technical University of Crete (TUC) and consists of a multidisciplinary team of seven partners from six countries. The project intends to develop a calibrated multi-criteria decision support system (DSS) and a web-based geographic information system platform accessible to water stakeholders and policy makers. The DSS and the platform, combined with a specific animation activity, will allow: (i) the engagement of social actors in a learning process around water issues at the watershed scale, based on the visualization of interactive thematic maps, (ii) the use of advanced technologies and tools, such as optical sensors and remote sensing capabilities for participatory water monitoring, and (iii) the use of calibrated numerical models for the spatio-temporal simulation of water quantity and quality evolution. Sustain-COAST thus explores new governance approaches to effectively support the conservation of coastal aquifers against anthropogenic and climatic pressures, through the promotion of innovative water management concepts based on the 4R principles: Reduce; Recycle; Reuse and Recover.
Although various measures have been taken by the administrations and agencies of the Mediterranean countries to promote a more integrated and sustainable management of coastal water resources, various management weaknesses persist: pollution from industrial and agricultural activities and poor wastewater treatment (Tunisia), water misuse from the agricultural/tourism sector and marine intrusions (Greece), excessive consumption by the agricultural sector (Turkey), and conflict between farmers and fishermen over eutrophication problems in wetlands used for both aquaculture and agricultural activities (Italy). These four countries seek to contribute to the improvement of the governance of Mediterranean coastal water resources through a collaborative research project that is designed to explore, design and test innovative governance approaches for coastal groundwater resources in the Mediterranean by promoting stakeholder dialogue and – decentralization and civil society engagement in decision-making processes.

The overall objectives of SUSTAIN-COAST are:

  • Design and test innovative governance approaches for Mediterranean coastal water resources;
  • Improve water resources management;
  • Mitigating pollution of water resources;
  • Application of good governance principles: equity, legitimacy, efficiency, transparency and accountability;
  • Decentralization, engagement of civil society in decision-making processes, engagement of the private sector in strong public-private partnerships.

The project is organized around 4 founding pillars:

  • Strengthening desirable coastal water resources management options;
  • Prevention of coastal groundwater pollution;
  • Active engagement of relevant stakeholders in a social learning process;
  • Strengthening monitoring, communication and dissemination activities.

The project is innovative in that it actively engages stakeholders throughout the basin in a social learning process and spatio-temporally predicts groundwater flow and pollutant transfer based on prevention and mitigation options suggested by stakeholders and climate change scenarios.

Responsible entity

The Technical University of Crete (UTC) is the coordinator of the SUSTAIN-COAST project. UTC has over 6000 students and 115 faculty members. UTC consists of five engineering schools and conducts research in advanced technological fields in collaboration with other research institutes and industries. The SUSTAIN-COAST project is carried out at the School of Environmental Engineering (EnvEng). Research at EnvEng aims to develop innovative solutions to the most daunting environmental challenges. Whether it is waste management, future energy needs, water resources or climate change, EnvEng’s research efforts are strengthened by creative collaborations with leading research institutes and universities around the world. Through various national and international projects, EnvEng has developed significant expertise in coastal groundwater resource management in relation to numerical modeling activities and GIS tools. These topics are directly related to the Sustain-COAST challenges.

Institutional setting

The need to implement innovative governance of coastal aquifers, taking into account technological development as well as socio-economic factors, has become a global necessity. In line with the challenges and scope of theme 1.1.2 of the PRIMA call “Sustainable and Integrated Water Management”, Sustain-COAST has been designed to explore innovative approaches to coastal aquifer governance among multiple water users and beneficiaries, under the uncertainties posed by changing climatic conditions, in four Mediterranean countries.
The technical partners of the project are the Helmholtz Center for Environmental Research (Germany), the Euro-Mediterranean Information System on Water Expertise (SEMIDE, France), the University of Strasbourg (UNISTRA, France), the University of Sassari (Italy), the Center for Research and Technology in Water (CERTE, Tunisia), the University of Mersin (Turkey).
A scientific council has also been appointed with institutes (GWP, CIHEAM – Bari institute, UFM – Union for the Mediterranean) and companies (Ambienta).

Geographical setting

The project takes place in 4 study sites, called “Living labs”: Arborea (Italy), Wadi El Bey (Tunisia), Malia (Greece), and Erdemli (Turkey).

Arborea (Italy): The case study is located in a 60 km2 area under the domain of the Consorzio di Bonificadell’Oristanese, a local consortium controlled by the regional administration that is responsible for the distribution of irrigation water supplied by the Eleonora d’Arborea dam, one of the largest in Europe. Agricultural systems range from dairy cattle breeding in a nitrate vulnerable area (the municipality of Arborea) to rice cultivation (over 3,000 ha), horticulture and other rain-fed agricultural activities. Water is key to the economic development of the district: the cooperative system of Arborea is the most important dairy industry on the island, with more than 300 million euros of annual gross income, struggling between the market crisis and the environmental restrictions of effluent management in an area that was drained in the 1930s with a very shallow water table and sandy soil. Rice cultivation is one of the largest consumers of water per unit area in the district, while providing not only food but especially rice seed. Horticulture is one of the main operations on the island, producing artichokes, melons and many other valuable crops.
Wadi El Bey (Tunisia): The Wadi El Bey pilot site is located about 40 km south of the Tunisian capital. It covers an area of 430 km². It is bordered to the north by the Gulf of Tunis and the hills of Tekelsa, to the west by the mountains of Bouchoucha and Halloufa, to the south by the hills of Hammamet, and to the east by the mountain of Abderrahman and the highlands of the eastern coast. The main wadi of this pilot site flows into the Sebkha El Maleh, which is close to the Mediterranean Sea. This pilot site contains various industries operating mainly in the field of textiles and food processing. In addition, it contains extensively cultivated areas (citrus, oranges, grapes and vegetables). The site is characterized by a high level of pollution due to the important development of industrial, agricultural and tourist activities. The main sources of pollution are industrial and agricultural activities and inadequate wastewater treatment.

Malia (Greece): The Malia watershed is located in northern Crete, Greece, 40 km east of the city of Heraklion. Surface and groundwater are used to support the extensive agricultural activity of the area, while in the last 20 years, increased tourism development has resulted in a significant demand for water consumption. The region’s water resources are very important to its inhabitants as they cover their drinking water needs and their well-being depends on agricultural and tourism activities that consume large amounts of water. As a result, groundwater levels have been significantly reduced over the past 30 years, resulting in significant saltwater intrusion into the groundwater. Water quality in the area has been significantly degraded due to the massive saltwater intrusion into the aquifer. As a result, high concentrations of Cl- are found in the groundwater, which, in conjunction with excessive pumping, leads to lower aquifer levels and groundwater degradation. In addition, increased concentrations of nitrates are also found in groundwater due to extensive agricultural activity in the area.

Erdemli (Turkey): The Erdemli coastal aquifer is located about 30 km west of downtown Mersin (in SE Turkey), covering an area of 45 km2. The population of Erdemli district is 140,331 people, the majority of whom are mainly engaged in agricultural activities. A significant part of the area is made up of agricultural areas such as greenhouses and citrus orchards. The southern part of the ACE area, which is very close to the Mediterranean coast, is mainly composed of alluvial deposits, while the northern highlands are composed of carbonate rocks with many karst features (e.g. sinkholes, caves, etc.). In the region, mainly in the Mediterranean coastal areas, groundwater from the coastal aquifer is used extensively to meet domestic and agricultural irrigation water demands. The main problems in the region are the intensive use of groundwater, the decrease in the quantity and quality of surface and groundwater due to increasing droughts, agricultural activities, and the lack of water quality.

Detailed explanation

The management practice is developed around a multi-criteria DAS (GIS-based multi-criteria decision analysis method) and multi-actor platforms (Living Labs). The DAS is based on multi-criteria factors including local and specific social, economic, technical and environmental constraints. This system is designed and implemented for each case study. The decision rules for the implementation of the DAS depend on quantitative data derived from weighted GIS (Geographic Information System) layers and thematic maps are created for each main criterion. At a later stage, sensitivity and suitability maps are produced using a weighted overlay method in GIS based on the weighted thematic maps. Finally, several “what-if” scenarios are developed and evaluated, considering a wide variety of water management issues, such as satisfaction assessment, water pricing, water saving suggestions to users, new infrastructure proposal and their impact. The ranking of these different alternatives in order of preference can also take place through the use of DAS by considering the principles of game theory in terms of a zero-sum game.

The data sources are scanned and transferred into a GIS tool (ArcGIS), and all data layers are georeferenced with the same projection system. Then all necessary data in the layers will be digitized using the Arc Editor tool. After digitizing the data, vector maps are created for each factor and the attributes are entered manually (lithology, land use and soil type, transmissibility, piezometric water levels and water quality parameters) or calculated automatically (distance to lineaments, springs and wells, water bodies) using the ArcGIS tools. All created vector layers are converted to raster format and each sub-criterion is weighted by the value of the assessment. The last action is the creation of the suitability map using the Weighted Linear Combination (WLC) aggregation method with the special data available for each case study area that may cause stress on groundwater pollution.

nappes du fossé Rhénan

Finally, a multi-stakeholder platform involving relevant actors, based on participatory and interactive sessions – Living Labs – is designed and implemented by the partners in each case study. The main stakeholders interested in the implementation of an innovative governance of the studied sites, taking into account their priorities but also their constraints, are taken into consideration. Consolidating and maintaining the active involvement of the main socio-economic actors concerned (ensuring a public-private-popular partnership) through their early involvement in the overall management and effective governance of the coastal aquifers of the selected case study sites are two of the objectives of Sustain-COAST. To this end, five living labs in each case study are co-designed and organized. The ultimate goal of this task is to promote social learning spaces, where integrated scientific and local knowledge is developed to support decision makers in designing adaptive pathways for local communities regarding sustainable water resource systems.

Historical overview

Two main triggers initiated the setting up of this project. First, climate change and its impacts on the groundwater resources of the selected study sites, and second, the absence and lack of data sharing among stakeholders.
No major obstacles were encountered during the project set-up phase. During the implementation phase, the obstacles encountered concerned the commitment of public decision-makers, access to data, and the management of the participatory approach in the context of the COVID-19 pandemic.
The main key factors of implementation were the Grenelle II law (n°2010-788) of July 12, 2010 and the need to delimit the protection areas of the catchments for drinking water and to set up action programs on these catchment areas.
The main obstacles were the lack of lobbying, as the estimation of the groundwater residence time was not imposed, and the financial leverage as this innovative method requires an expertise with a certain cost that can slow down its use.

Evidence of benefits from implementation

There are no benefits to the use of this management practice yet since the project is still in progress. However, interesting first results on the characterization of the demonstration sites and on the cost-effectiveness and cost-benefit analysis of some prevention scenarios have been published on the project’s institutional website.

Replication potential in SUDOE region

The project has a strong potential for replication (Mediterranean or wider) as it touches different stakeholders and different groundwater issues that are common to other regions. The financial cost of such a project is 1.12 M€, with about 15 people (6 countries, 7 partners) dedicated to the implementation of the solution. Each partner was able to benefit from subsidies via the PRIMA program.

Future outlook

The short-term perspective of the project is to extend it by one year because it has been strongly impacted by the COVID-19 crisis. In the longer term, the objective is to valorize the Sustain-COAST results by creating new projects (2 PRIMA projects have been created INTheMED and AgreeMED), and to transfer tools and practices to the groundwater resources managers of the demonstration sites.

Key points of the innovative method

> Multi-partner project
> New governance approach to protect coastal aquifers
> Living laboratories for a participatory approach
> Civil society engagement in the decision-making process
> Social learning process

Acknowledgements

The innovative practice was suggested by Yvan KEDAJ (Aqua-Valley) and Maroua OUESLATI (SEMIDE) participated in the interviews.

References

Sustain-Coast (2020). Deliverable 2.1 : Report on the real sites characterization : https://www.sustain-coast.tuc.gr/fileadmin/users_data/project_sustain_coast/Sustain-COAST_D2.1__1_.pdf – consulté en ligne le 14 janvier 2022.

Ben-Salem, N., Wachholz, A., Rode, M., Borchardt, D., Jomaa, S. (2020). Evaluation of three global gradient-based groundwater models in the Mediterranean Region. EGU General Assembly 2020, https://doi.org/10.5194/egusphere-egu2020-8237

Karatzas, G., Vozinaki, A-E., Anyfanti, I., Stylianoydaki, C., Varouchakis, E., Goumas, C., Roggero, P-P., Mellah, T., Akrout, H., Jomaa, S. (2021). Living labs towards sustainable groundwater management: case study in Malia, Crete, Greece. EGU General Assembly 2021, https://doi.org/10.5194/egusphere-egu21-7941

INTERNET REFERENCES:

Site web du projet : https://www.sustain-coast.tuc.gr/en/home – consulté en ligne le 14 janvier 2022
Publications liées au projet Sustain-COAST : https://www.sustain-coast.tuc.gr/en/dissemination/publications-and-scientific-articles – consulté en ligne le 14 janvier 2022
PRIMA : https://www.horizon2020.gouv.fr/cid137439/publication-de-l-appel-2019-du-programme-prima.html – consulté en ligne le 14 janvier 2022
Université Technologique de Crête : https://www.tuc.gr/index.php?id=5397 – consulté en ligne le 14 janvier 2022
Helmholtz Centre for Environmental Research : https://www.ufz.de/index.php?en=33573 – consulté en ligne le 14 janvier 2022
SEMIDE : http://www.semide.net/fr – consulté en ligne le 14 janvier 2022
Université de Strasbourg : https://www.unistra.fr/ – consulté en ligne le 14 janvier 2022
Université de Sassari : https://en.uniss.it/about-uniss/francais/luniversite-de-sassari – consulté en ligne le 14 janvier 2022
CERTE : http://www.certe.rnrt.tn/ – consulté en ligne le 14 janvier 2022
Université de Mersin : http://www.mersin.edu.tr/ – consulté en ligne le 14 janvier 2022

aquifer
news

Discover more on the Aquifer project news and on aquifer management

aquifer news

Description and objectives of the project

The scientific community recommends a substantial improvement in the knowledge of aquifers, the establishment of reliable monitoring networks and a greater involvement of the administration and users to achieve a sustainable management of aquifers. The main objective...

read more

Information on the project

The Llobregat Delta Water Users' Community has designed recharge basins in Molins de Rei to recharge the Baix Llobregat aquifer. View of one of the reloading basins during the test phase The Llobregat Delta Water Users' Community is one of the nine partners in the...

read more

Success stories in groundwater management

Compilation of groundwater management success stories completed. Throughout April, the 30 cases of innovative practices in groundwater management have already been selected by the clusters participating in the project: PPA, CWP and AV. The task started with the...

read more
See all news

PROPOSE AN
INNOVATIVE PRACTICE

You are in charge of an innovative practice regarding aquifer management and you want to referenced it on the Aquifer platform ?

Fulfill the form and propose it to the Aquifer partners.

let's go

THE EBOOK

Aquifer offers a range of innovative water management practices. You can download all our fact sheets here.

e-book of innovative practices

DOCUMENTATION

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To go further

Groundwater dating by CFC and SF6 (France)

by | Aug 24, 2022

Groundwater

dating by CFC and SF6 (France)

GROUNDWATER

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People in charge of the innovative practice :

Virginie VERGNAUD – virginie.vergnaud@univ-rennes1.fr

Groundwater dating by chlorofluorocarbon (CFC) and sulfur hexafluoride (SF6) dating is a geochemical analysis methodology for estimating the mean turnover time of groundwater. This methodology is developed by the CONDATE-Eau platform of the University of Rennes 1 in France. This expertise is carried by only 8 laboratories in the world, and allows a fine analysis (in picograms per liter), where conventional analyses are generally in micrograms per liter. The use of these tracers allows the understanding of the functioning of aquifer systems via circulation models. CFCs are gases known for their impact on the ozone layer, and there are no more emitting countries. There are three main sources of CFC emissions: polystyrene foams (CFC-11); refrigerators (CFC-12); and solvents (CFC-113). SF6 is used as an electrical insulator. This methodology was developed in groundwater following the intensification of agricultural practices in the 1970-1980s and a significant increase in nitrate releases. The objective of this methodology was to estimate the residence time of nitrates that move at the same speed as water. The tool is now used by communities, engineering companies, and university laboratories as a management tool for aquifer systems to reveal the time needed before observing the effects of action programs aimed at limiting nitrate inputs on a territory. It is also a communication tool for farmers and field actors to show them the time frame in which the results of their efforts will be visible.

Responsible entity

The CONDATE-Eau Platform is the entity responsible for this innovative management practice. It is a platform of the University of Rennes 1 that offers services in hydrogeology and residence time estimation to communities, engineering agencies, and other academic partners.

Institutional setting

Since 2000, the Water Framework Directive (WFD) has set ambitious objectives in terms of restoring the quality of water resources (whether they are intended for drinking water supply or not). Within the framework of this directive, the member states of the European Union must act in particular to protect their drinking water catchments in order to reduce the treatments applied to the water extracted and to fight against the deterioration of the quality of the resource. The water bodies used for water catchments for human consumption (or which may be used in the future) are listed as protected areas. In France, the law on water and aquatic environments (LEMA, n°2006-1772, article 21) and the decree of 14 May 2007 (n°2007-888) have reinforced the existing regulatory tools. These texts have made it possible to use the “Environmentally Restricted Areas” (ERA) system on catchments. This device can be used on the scale of the catchment area (AAC is the French term) presenting a particular challenge for the current or future supply of drinking water (quantitative and qualitative protection of drinking water catchments). Subsequently, the Grenelle Environment Forum confirmed the importance of the protection of water catchments intended for drinking water supply. The implementation of the Grenelle conclusions (article 27 of the law n°2009-967 of August 3, 2009) thus provides for the protection of a little more than 500 catchments among those most threatened by diffuse pollution as of 2012.

Geographical setting

The practice is carried out on all types of aquifers on an international scale. Several examples of the use of this practice have been carried out in France, Brazil, India, Quebec, etc. There are about 30 projects per year on average of groundwater dating by CFC and SF6, of which 15% are carried out on an international scale.

Figure 2: Location of CFC and SF6 dating studies conducted by CONDATE-Eau.

Detailed explanation

The estimation of the mean turnover time of groundwater is a geochemical analysis methodology that allows the dating of groundwater from CFC and SF6 gases. The principle is that these tracers tell us the time it took for the water to travel between its point of infiltration and its point of withdrawal. Indeed, once the gases are dissolved in the water table, they isolate themselves and keep their atmospheric signature.

nappes du fossé Rhénan

Figure 3: Schematic diagram of CFC and SF6 dating: recording the atmospheric signature.

However, a catchment is fed by a multitude of water drops that have different ages, so we can only estimate the average renewal time of the water table as a whole, we thus speak of average age or apparent age.
The understanding of aquifer functioning is thus achieved via circulation models observed in the environment, which represent either open aquifers, confined aquifers, or a mixture of both. The average age of the water table is then interpreted on the basis of 3 simple hydrogeological models: (i) piston, (ii) continuous recharge, and (iii) binary mixing.
For the piston model, all water lines have the same age and therefore all tracers are consistent. The recharge zone is then localized and isolated during the groundwater flow.

nappes du fossé Rhénan

Figure 4: Piston circulation model.

For the exponential or continuous recharge model: the recharge is carried out on the whole catchment area at a given point, i.e. a mixture of water of all ages, the distribution thus corresponds to an exponential distribution. The time obtained is the average age for which 2/3 of the water table has been renewed.
For the binary mixing model, it is a mixture between two distinct and restricted recharge zone water masses in its simplest form. It can be infinitely complexified.

Historical overview

  • 2005: first work on CFC dissolved gases in the framework of a regional project. This period also corresponds to the end of the thesis of V.Ayraud-Vergnaud on the estimation of water residence times in relation to algae in Brittany.
  • 2007: creation of the LADES (Laboratoire de Datation des Eaux Souterraines) consultancy for the estimation of water residence times for communities. Valorization of the thesis work via a Young University Company.
  • 2010: closing of the company and beginning of autonomy of the universities.
  • 2011: Opening of the CONDATE-Eau platform within the University of Rennes 1 (OSUR-Observatoire des Sciences de l’Univers de Rennes – CNRS-UR1).
    The main key factors of implementation were the Grenelle II law (n°2010-788) of July 12, 2010 and the need to delimit the protection areas of the catchments for drinking water and to set up action programs on these catchment areas.
    The main obstacles were the lack of lobbying, as the estimation of the groundwater residence time was not imposed, and the financial leverage as this innovative method requires an expertise with a certain cost that can slow down its use.

Evidence of benefits from implementation

The main advantage of using this methodology is the homogeneity of the gas releases on an international scale. Indeed, we know the evolution curves of the release of these products which are homogeneous on the whole Northern hemisphere. These gases, banned since the Kyoto Protocol and Montreal in 1992, are very stable gases that have remained in the atmosphere.
Several references (thesis, platform website, institutional reports) demonstrate the interest of using these groundwater dating methodologies for the management of aquifer systems.

Replication potential in SUDOE region

The methodology has a strong potential for replication with more than 50 international references. But beware that this methodology cannot be extrapolated to pesticides which have different transfer times from water.

Figure 5: Chronic air concentrations of CFCs and SF6 in the Northern Hemisphere.

The implementation of this practice required the purchase of equipment (100 k€), the launch of a thesis, the recruitment of a study engineer (1 full-time) for development, and the presence of a research engineer.
Today, the human resources dedicated to the management of the practice are 4 people (2 full-time), with a study engineer on a fixed-term contract for logistics and analyses, and a research engineer on a permanent contract for coordination. Finally, two other research engineers are needed for R&D developments.
Water dating services for local authorities can be subsidized by the water agencies, up to 50-80%. The equipment (investment and renewal) can be subsidized by the State-Region Plan Contracts.

Future outlook

In the short term, the prospects for development are to move on to other types of studies: (i) tracing and measurement by continuous dissolved gas, and (ii) organic geochemistry for the identification of faecal contamination. For the long term, the objective is the monitoring of emerging gases, but technical barriers must be removed because they are not persistent in the atmosphere.

Key points of the innovative method

> Estimation of aquifer turnover time via CFC and SF6 tracers
> High replication potential: all types of aquifers on an international scale
> Evaluate the reactivity of the aquifer to recharge modalities
> Evaluate the time necessary before being able to observe the impacts of action programs

Acknowledgements

The innovative practice was suggested by Yvan KEDAJ (Aqua-Valley) and Virginie VERGNAUD (University of Rennes 1) participated in the interviews.

References

Ayraud, V. (2015). Détermination du temps de résidence des eaux souterraines : application au transfert d’azote dans les aquifères fracturés hétérogènes. Thèse de doctorat, Universités Rennes 1, France, 313 p. https://tel.archives-ouvertes.fr/tel-00088100/document – Consulté en ligne le 24 janvier 2022.

Antea-Group (2019). Estimation du temps moyen de renouvellement de l’eau par datation à partir des CFC et SF6. Résultats 2018 sur les captages prioritaires en eau souterraines du Sud du bassin. https://www.eaurmc.fr/upload/docs/application/pdf/2019-05/rapport-datation-2018_sud-bassin-rm-vf.pdf – Consulté en ligne le 24 janvier 2022.

Depardon, S., & Vergnaud, V. (2018). Estimation des délais de renouvellement des aquifères : méthodes et premiers résultats sur les captages du bassin Rhône Méditerranée. Une aide pour orienter les opérations de restauration de la qualité ? Journée eau & connaissance, Université Lumière Lyon 2, le 6 décembre 2018. https://docplayer.fr/144441949-Depardon-stephane-antea-group-vergnaud-virginie-plateforme-condate-eau-osur-univ-rennes.html – Consulté en ligne 24 janvier 2022.

INTERNET REFERENCES:

Plate-forme Condate-Eau : https://osur.univ-rennes1.fr/condate-eau

Protection des captages contre les pollutions diffuses : le contexte réglementaire. https://aires-captages.fr/page/contexte-reglementaire

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