AgrHys observatory

AgrHys observatory

Scientific context

The AgrHys observatory is located in Brittany, which has an oceanic climate. It includes two sites representative of the intensive agricultural systems of Western Europe combining animal and crop productions. Kebernez site (Plomelin, South Finistère) represents a 1,3 km² area. It is granitic and characterized by a rainfall of 1000 mm/an and it used for dairy farming and polyculture (rotation of corn, wheat, meadow). Kervidy-Naizin watershed (Josselin, Morbihan), is a second-order watershed with an area of 5 km², drained by Coët-Dan, a tributary of the Evel. It is developed on brioverian shale and rainfall is 800 mm/year.  Intensive farming (dairy and pig) is predominant. Coët-Dan stream is intermittent and generally flows only between November and the end of June.


Starting year: 1980-1990

Localisations: Brittany, South Finistère , Morbihan

Keywords: oceanic climate, granite and shale, intensive agrosystems, hydrology, biogeochemistry


Web site:

PIs: Ophélie FAUVET et Laurent RUIZ

Bassin versant de Kervidy-Naizin avec vue sur le RiverLab
Kervidy-Naizin catchment with the RiverLab © Hubert Raguet

Scientifique questions

The main question of the AgrHys observatory is the response time of hydrogeochemical flux to climatic and anthropogenic forcing within agrosystems. Catchments in Brittanny are impacted by a very strong agricultural pressure involving modifications of the water cycle and a perturbation of biogeochemical cycles, in particular that of nitrogen. This question is addresses through several actions of research relating to:

  • Water transfert times within the Critical Zone and the recharge process of aquifers;
  • Hydrological response times to climate and anthropogenic changes;
  • Modification of major biogeochemical cycles (carbon, nitrogen, phosphorus) at different time scales (1 month to 50 years) and the role of « hotspots » (wetlands, hedgerows);
  •  The influence of massive inputs of agricultural origin on stocks, processes, chemical erosion and soil formation.

Sites and variables measured

Nazin site and its sub-basin of Kervidy are instrumented for the different comparrments of the Critical Zone: atmosphere, soil, groundwater. Land use is monitored. The site has a meteorological station, a flux tower, 15 piezometers and a limnimetric station for a high frequence monitoring of water quality at the outlet: biogeochemical measurments (carbon, nitrogen, phosphorus), suspended matter and turbidity. The installation of a « Riverlab » (Equipex « CRITEX » funding, 2012-2022) at the Naizin watershed outlet allows the collection and the analysis of high frequency biogeochemical variables (main ions, dissolved carbon, nitrate, phosphate and emerging contaminants – chemical residues, etc.)

Kerbernez site is composed of five sub-basins with an area ranging 10 ha to 60 ha (Puits, Coat Timon, Ty Garde, Pont Lenn et Nead Meur). Puits basin is itself divided into three sub-basins (Kerbernez, Kerrien and Guerveur). Measured variables are hydrological, hydrochemical and climatic variables and allow studying specifically the functioning of groundwater recharge. The site is highly instrumented and includes 7 limnimetric stations, 31 piezometers (placed at different depths), 1 battery for 5 tensiometers, 1 meteorological station, weirs for flow measurements and 4 stations for a continuous measurement of soil moisture. Agricultural practices are also monitored.

Partners and further information

The observatory is managed by the UMR Sol, Agro & Hydrosystèmes Spatialisation (SAS, Inrae-Agrocampus) of Rennes in collaboration with Géosciences Rennes and the UMR COSTEL of Rennes. It is part of the OSU de Rennes-OSUR and it is supported by local supports from the Départment, INRAE and the Ministère de l’Enseignement Supérieur, de la Recherche et de l’Innovation. The site collaborates with the Zone atelier Armorique (ZAAr), which is part of the network of Zones ateliers. AgrHys is integrated in the European (eLTER RI) and international (ILTER). Naizin site is one of the French sites particpating to the European project eLTER PLUS of eLTER RI.