Goncalves J., Petersen J., Deschamps Pierre, Hamelin Bruno, Baba-Sy O. (2013). Quantifying the modern recharge of the "fossil" Sahara aquifers. Geophysical Research Letters, 40 (11), p. 2673-2678. ISSN 0094-8276.
Titre du document
Quantifying the modern recharge of the "fossil" Sahara aquifers
Goncalves J., Petersen J., Deschamps Pierre, Hamelin Bruno, Baba-Sy O.
Source
Geophysical Research Letters, 2013,
40 (11), p. 2673-2678 ISSN 0094-8276
The North-Western Sahara Aquifer System (NWSAS), one of the world's largest groundwater systems, shows an overall piezometric decline associated with increasing withdrawals. Estimating the recharge rate in such a semiarid system is challenging but crucial for sustainable water development. In this paper, the recharge of the NWSAS is estimated using a regional water budget based on GRACE terrestrial water storage monthly records, soil moisture from the GLDAS (a land data system that assimilates hydrological information), and groundwater pumping rates. A cumulated natural recharge rate of 1.40 +/- 0.90 km(3) yr(-1) is estimated for the two main aquifers. Our results suggest a renewal rate of about 40% which partly contradicts the premise that recharge in this area should be very low or even null. Aquifer depletion inferred from our analysis is consistent with observed piezometric head decline in the two main aquifers in the region. Annual recharge variations were also estimated and vary between 0 and 4.40 km(3) yr(-1) for the period 2003-2010. These values correspond to a recharge between 0 and 6.75 mm yr(-1) on the 650,000 km(2) of outcropping areas of the aquifers, which is consistent with the expected weak and sporadic recharge in this semiarid environment. These variations are also in line with annual rainfall variation with a lag time of about 1 year.
