Pierre Deschamps, Bruno Hamelin, (Cerege)
Chloé Poulin (PhD, Cerege)
Camille Bouchez (post-doc, Cerege and Flinders University, Australia)
Worldwide demographic pressure, urbanization, economic growth and development of irrigated agriculture all contribute to massive increases in water demand that seriously jeopardize the availability, quantity and quality of the water resource. The Maghreb and the circum-Sahara area are particularly vulnerable to these threats because climate change amplifies this water stress by impacting the water balance as a whole, and groundwater recharge in particular. In these regions, groundwater is of strategic importance since surface water bodies are scarce.
However these massive deep groundwater reservoirs that were artesian basins in majority are subject to intense mining since the 1950’s. This has led to a substantial decline in the piezometric surface, as witnessed by the drying up of naturally flowing springs, drawdowns in pumped wells or loss of artesianism. This raises the question of the renewability and sustainability of this resource.
In order to face this challenge, this project aims at better describing the modern and past recharge of two aquifer systems : the North-Western Saharan Aquifer System (NWSAS) and the Nubian Sandstone Aquifer System (NSAS).
- The water balance of three lake systems in the Tchad basin was quantified their hydrological was modelled.
- Lake Iro et Lake Fitri have a recharge time of 50-60 years whilst the Ounianga lakes have a recharge of ca. 10 000 years
- These results suggest that the wet period in central Africa around 10 000 years ago may have been due to an ingress of Atlantic humid air masses rather than to a Northward shift of the monsoon as previously thought (debate still underway).
- Aquifers in the Sahel host a significant amount of renewable water, which could therefore be used as a strategic freshwater resource
(Bouchez et al. 2019)