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 is comprised of watersheds with a drainage area of about 10,000 km² each. These sites are at different latitude in order to sample the ecoclimatic gradient, characteristic of this region.
Listed 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 ~ 1,200 mm/year).
A fourth site was installed in Sahelian Senegal in 2013 and samples the East-West longitudinal gradient.
Starting year: 1990 (Niger), 1996 (Benin), 2005 (Mali), 2013 (Senegal)
Locations: Mali, Benin, Senegal and Niger
Key words: monsoon, Sahelian and Sudanian climate, nested sites, hydrology, evapotranspiration, water resources
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 aims to:
- Understand the main processes governing water and vegetation cycles;
- Provide a regional vision of the evolution of the environmental systems;
- Improve modelling of continental surfaces processes in Western Africa;
- Provide tools to decision makers and public actors.
Sites and measured variables
Observation are carried out at different spatial 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: meteorology (rain, wind, pressure, temperature and radiation), surface waters (rivers in humid climates or ponds in more arid climates), groundwater level and quality. In addition to the above measured variables, local intensive sites include measurements of water infiltration (soil moisture over 2 meters), evapotranspiration (from trees, crops or bare soil) via flux towers, and vegetation (biomass, height, sap flux). In total, the system represents nearly 280 measurement sites (850 sensors), recording more than 2,500 data per hour across 4 countries.
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) in 2005 and obtained the “IRD South label” in 2015. AMMA-CATCH is part of 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).