AMMA-CATCH observatory

AMMA-CATCH observatory

Scientific context

West Africa is a region in a rapid transition in terms of climate, demography and land use. In this context, the AMMA-CATCH long-term observatory has been developed to monitor the impacts of global change on the Critical Zone of West Africa and to better understand its current and future dynamics. The observatory relies on sites about 10 000 km² each. These sites are staggered in latitude in order to sample the ecoclimatic gradient, characteristic of this region. From north to south we find: the Gourma site (Mali) in a semi-arid climate (rainfall ~ 300 mm/year), the Niamey square degree site (Niger) in a Sahelian climate (rainfall ~ 600 mm/year) and the Upper Ouémé site (Benin) in a Sudanian climate (rainfall ~ 1200 mm/year). A fourth site was installed in Senegal in 2013, sahelian, and allows to sample the East-West longitudinal gradient.


Starting year: 1990 (Niger), 1996 (Benin), 2005 (Mali), 2013 (Senegal)

Localisations: Mali, Benin, Senegal and Niger

Key words: monsoon, Sahelian and Sudanian climate, nested sites, hydrology, evapotranspiration, water resources


Web site:

PIs: Sylvie Galle,
Manuela Grippa,
Christophe Peugeot,

Le site de Hombori pendant la saison des pluies (Mali)
Hombori site during the wet season (Mali) © Eric Mougin

Scientific questions

What is the impact of climate changes and land use on water and vegetation cycles in West Africa ? The long term observations of the AMMA-CATCH observatory aim to:

  • Understand the main processes that govern water and vegetation cycles;
  • Provide a regional vision of the evolution on the environmental systems;
  • Improve the modelling of continental surfaces in West;
  • Provide tools to decision makers and public actors for decision support.

Sites and measured variables

The observation strategy is based on a nesting of scales. The observation of hydrologic processes is reinforced on “supersites” (~ 100 km²) and the monitoring of vegetation dynamic and associated water flux is done on “local intensive sites” (~ 1 ha²) which represent the main vegetation cover of the site considered.

AMMA-CATCH sites are instrumented to provide homogenous data (same instruments, same protocols for data processing) on the same variables: the AMMA-CATCH sites are equipped to provide homogeneous data (same instruments, same protocols for data processing) on the same variables: meteorology (rain, wind, pressure, temperature and radiation), surface water (rivers in humid climates or ponds in more arid climates), water table height and quality On the local intensive sites, in addition to the above measured variables, additional measurements of water infiltration into the soil (soil moisture over 2 meters), evapotranspiration (from trees, crops or bare soil), in particular via flux towers, and vegetation development (biomass, height, sap flux) are done. In total, the system represents nearly 280 measurement sites (850 sensors) that enable to record more than 2,500 measurements per hour all over 4 countries.

Piezometric (pan pipes) ans oil measurements in a lowland (Benin) © JM.Cohard
Soil moisture measurements at several depths
in a soil pit (Mali) © JM.Cohard
Micrometeorological tower for measuring the energy balance at the surface, in articular evapotranspiration and CO2 fluxes (Niger) © JM.Cohard

Partners and further information

AMMA-CATCH is led by the Institute of Environmental Geosciences (IGE), Grenoble, in collaboration with Géosciences Environnement Toulouse (GET) and HydroSciences Montpellier (HSM). The observatory has African partners in Benin (Abomey Calavi University  and Parakou University, Direction générale de l’Eau), Niger (Abdou Moumouni University, Maradi University and Zinder University), Mali (University of Science, Technique and Technologies – U.S.T.T.B, Bamako) and Senegal (Cheikh Anta Diop University, Dakar and the Senegalese Institute for Agricultural Research – ISRA/CRZ).

The observatory was labelled “Observatoire de Recherche en Environnement” in 2002, Service national d’observation (SNO) since 2005 and obtained the “IRD South label” in 2015. AMMA-CATCH is part of the OZCAR-RI since its creation in 2017 and receives recurrent financial supports from IRD, CNRS-INSU, as well as Observatories in Universal Science – OSU (OSUG, OREME, OMP).