OBSERVIL OBSERVATORY

Scientific context

Scientific questions

The main objective of SNO Observil is to study the flows of water, air, energy and matter in urban environments, across the compartments (air, water, soil, built environment) that make up the urban critical zone, in relation to changes in the way urban areas are used and managed. This study involves the physical and biogeochemical characterisation of urban areas in the various geographical and climatic contexts present in the network of participating observatories. The cross-referencing of data from the various disciplines involved (hydrology, biogeochemistry, climatology, building heating, remote sensing) should make it possible to adopt integrated approaches to urban environments, making it easier to understand the processes governing the functioning of this urban critical zone.

The scientific questions are targeted at the issue of assessing the impact of global changes in cities, and concern in particular: 

• Knowledge of balances (water, energy, matter) and interactions between compartments (air, water, soil, built environment) ;
• Identifying the types of urban morphologies (forms, characteristics, uses) that can limit the risks ;
• Defining relevant indicators for developers and operational staff ;
• Understanding the impact of adaptation solutions (such as nature in the city).

Sites and measurements

The network’s observation approach is multi-variable and multi-scale (from the stormwater management facility to the agglomeration) and integrates several compartments (air, water, soil, built environment). The characterisation of these compartments of the urban critical zone is based on three research topics: hydrology and biogeochemistry of water and soil, climatology as well as building heating and remote sensing. In each area, the variables have been selected on the basis of their relevance to a systemic approach to urban areas. The data collected come either from one-off campaigns, whether regular or not, or from continuous monitoring.

The network relies on 11 observatories, which are composed of one or more long-term instrumented sites located in the same urban area. These sites have contrasting urban morphologies and soil and climate constraints.

The 11 observatories of the network are:

• Dijon (MUSTARDijon)
• Île de France (OPUR)
• La Rochelle 
• Lyon (OTHU)
• Montpellier (OMSEV)
• Nancy (OTELo)
• Nantes (ONEVU)
• Orléans (OBSCURE)
• Rennes 
• Strasbourg 
• Toulouse 

The different sites of the network OBSERVIL are detailed hereunder :

• Dijon (MUSTARDijon)

The MUSTARDijon observatory (Measuring Urban System of Temperature of Air Round Dijon) covers the metropole of Dijon. Hourly meteorological measurements (temperature, relative humidity, global radiation, wind speed and direction) are taken in nearly 30 local authorities and 90 stations, the 50 oldest since 2014. The objectives are both scientific and applied: dynamic mapping of the Urban Heat Island, validation of climate model outputs or contribution to urban planning documents favouring Urban Freshness Islands.

• Île de France (OPUR)

The Observatoire des Polluants Urbains (OPUR) is a long-term research programme in the field of urban hydrology that has been running since 1994. It is based on a major observation infrastructure and a specific partnership between researchers and operational stakeholders in the water and wastewater sectors in the Ile-de-France region. Its aim is to gain a better understanding of the flow of water and contaminants in urban environments, from their source to their discharge into receiving environments, taking into account management structures. Spot or high frequency data have been acquired in various areas, and the knowledge gained is being used to develop tools to help manage water and pollutants in urban environments.

• La Rochelle 

As part of a project supported by the Région Nouvelle-Aquitaine, the observatory “La Rochelle” is willing to set-up instrumental monitoring of a neighbourhood undergoing renovation, with a network of microclimatic and building heating measurements, with the aim of evaluating a multidisciplinary and integrated approach to the study of energy consumption in relation to the urban microclimate. An island in the Villeneuve district “les Salines” is to be used as the basis for this experimental monitoring, and a microclimate and building heating monitoring system will be set-up.

• Lyon (OTHU)

The Observatoire de Terrain en Hydrologie Urbaine (OTHU) is a multidisciplinary observation and research facility focusing on urban discharges and their impact on receiving environments, with a view to proposing new solutions for the design and management of wastewater treatment systems. The research work carried out in support of the OTHU’s observations aims to i) understand the mechanisms underlying the circulation of water flows and contaminants in the urban environment, ii) understand the effects of urban discharges during rainfall on the functioning of groundwater and peri-urban rivers and iii) promote multi-scale and multi-actor management (particularly organisations) of urban water.

As part of a new observation project, CETHIL will be setting up energy monitoring for an urban district on the university campus “La Doua”, in order to study and assess the reciprocal effects of a building and its environment. A network of microclimatic and thermal measurements of the building will be set up. This site is not currently part of the OTHU.

• Montpellier (OMSEV)

The Observatoire Méditerranéen et au Sud de l’Eau dans la Ville (OMSEV) has been part of SNO Observil since 2020. It is managed by the JRU HydroSciences Montpellier. The observation site is located mainly in the Verdanson catchment area, a tributary of the River Lez, which flows through the city of Montpellier. This catchment has several characteristics typical of urban catchments: (i) short reaction times to rainfall events, (ii) a still growing urbanisation at the head of the catchment, and (iii) a high density of facilities and structures. The measurement network in place enables rainfall to be characterised with a high degree of spatial resolution (inter-measurement point spacing of the order of one hectometre) and temporal resolution (readings taken at 5-minute intervals). In addition, the Verdanson watercourse is instrumented at several points by Montpellier Méditerranée Métropole, which manages a fleet of water level sensors for warning purposes.

• Nancy (OTELo)

The urban soil observatory of the Observatoire Terre et Environnement de Lorraine (OTELo) is a network of sampling sites across the Grand Nancy metropolitan area, aimed at the study of soil quality and knowledge of urban soils for the sustainable development of cities. Soil samples are collected at 450 points on vegetated sites in Grand Nancy. The scientific specialties covered by the LSE and GISFI partners, provide a broad range of expertise in i) soil science, with the study of the pedogenesis of highly anthropized soils (in particular, the physicochemical processes involved in soil evolution), ii) geochemistry, with the analysis of contaminants and iii) agronomy, with the assessment of the effects of soil fertility and toxicity on plants, and the feasibility of phytoremediation. Finally, 4 lysimeters were installed in different vegetated areas to produce a complete hydrological budget on a local scale.

• Nantes (ONEVU)

The Observatoire Nantais des Environnements Urbains (ONEVU), which was set up in 2006 and accredited by the SNO Observil since 2020, has developed an observation and research activity on the flows of water, energy and pollutants at the soil/surface/atmosphere interfaces in urban environments. To study these flows, a physical and chemical observation approach has been set up and   encompasses the hydrological monitoring of several urban catchments, and a detailed monitoring of a 30 ha urban district, combining surface and soil hydrological measurements, heat flow measurements and a building thermal observation site. An urban network for measuring air temperature and humidity is being deployed in the urban area. These observation areas make it possible to address the themes of hydrology and urban climatology, the geochemistry of urban water and soil, building heating and urban remote sensing.

• Orléans (OBSCURE)

Located in the town of Semoy (45), the OBservatoire des Sédiments et de la Cascade sédimentaire en milieu URbain : cas de l’Egoutier à Semoy (Loiret) (OBSCURE) is a workshop site of the Zone Atelier Loire and is part of the SNO Observil. Covering 7.9 km², it is located to the east of the Orléans metropolitan area. This instrumented catchment area, now characterised by an upstream/downstream anthropisation gradient (forest land upstream and residential and industrial districts downstream), drains the Egoutier river, which is fed by rainwater and also by two wastewater treatment plant discharges. 22 stations are monitored for hydrosedimentary and geochemical parameters. 3 of these, installed at key points in the catchment, are equipped with autonomous sensors. At the heart of OBSCURE, the Etang de la Beulie allows sedimentary material to accumulate over 250 years.

• Rennes 

The observation system at the Rennes site, labelled SNO Observil and Zone Atelier Armorique, covers the Rennes metropolitan area. The scientific questions raised concern three main issues: observation of the earth using multi-sensor and multimodal imagery (drone, aircraft and satellite), urban climate from the scale of the neighbourhood to the urban area (https://run.letg.cnrs.fr/), and urban hydrology from the integrated rainwater management structure to the urban basin outlet, including water circulation in the ground and transfers to the groundwater.

• Strasbourg 

Strasbourg’s observation system, which has been accredited by the SNO Observil and Zone Atelier Environnementale Urbaine (ZAEU), focuses on the functioning of an urban socio-ecosystem centred on the urban area, as well as on the relationships that the urbanised area maintains with the socio-ecosystems that are connected to it, both functionally and socio-economically. The research activities are carried out in close collaboration with various departments of the city and Eurometropolis of Strasbourg, in particular through several instrumented sites that enable knowledge of the quality of these ecosystems (biotic and abiotic) to be acquired and enhanced. Observations, models and analyses are focused on energy, air pollution and climate; on the water cycle in urban and local environments; the relationship between the degree of urbanisation and the impact on ecological systems; on urban agriculture and links with biodiversity.

• Toulouse 

Toulouse Métropole’s CLIMATOLOSA urban network of weather stations was set up in 2016 in collaboration with the Centre National de Recherches Météorologiques – CNRM (CNRS & Météo-France) and includes 78 weather stations. The scientific challenge is to better document the spatio-temporal variability of the urban heat island, in various types of neighborhood throughout the urban area. However, it is also designed to provide better knowledge of the urban micro-climate in the area, and to identify areas of high heat or islands of coolness, so that the city can conduct urban planning actions to adapt to global warming.

Partners and further information

The SNO Observil has been accredited by the CNRS for 2020 and is coordinated by OSUNA, in collaboration with the Federation of research IRSTV (FR 2488). It relies on 7 observatories of the Universe – OSU (OREME, OSU EFLUVE, OSU THETA, OSUC, OSUNA, OSUR, OTELo), 6 Zones Ateliers (Armorique, Bassin de la Moselle, Bassin du Rhône, Environnementale Urbaine, Loire, Seine) et 2 federations of research (IRSTV and OTHU). It also collaborates with several institutional partners: cities, metropolis, departments, regions, trade unions, water agencies, etc.