Open AccessLocal and global hydrological contributions to time‐variable gravity in Southwest Niger
Author(s) -
Pfeffer Julia,
Boucher Marie,
Hinderer Jacques,
Favreau Guillaume,
Boy JeanPaul,
de Linage Caroline,
Cappelaere Bernard,
Luck Bernard,
Oi Monique,
Le Moigne Nicolas
Publication year - 2011
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2010.04894.x
Subject(s) - hydrogeology , aquifer , hydrology (agriculture) , groundwater , context (archaeology) , water table , geology , water storage , environmental science , geomorphology , paleontology , geotechnical engineering , inlet
SUMMARY Advances in methods of observation are essential to ensure a better understanding of changes in water resources considering climate variability and human activities. The GHYRAF (Gravity and Hydrology in Africa) experiments aim to combine gravimetric measurements with dense hydrological surveys to better characterize the annual water storage variability in tropical West Africa. The first absolute gravimetric measurements were performed in Southwest Niger, near a temporary pond where rapid infiltration to an unconfined aquifer occurs. As gravity is sensitive both to local and global variations of water mass distribution, the large‐scale hydrological contribution to time‐variable gravity has been removed using either GRACE satellite data or global hydrology models. The effect of the local water storage changes was modelled using in situ measurements of the water table, soil moisture and pond water level. The adjustment of these simulations to residual ground gravity observations helped to constrain the specific yield to a value ranging between 1.8 and 6.2 per cent. This range of value is consistent, albeit on the low side, with the aquifer water content (6–12 per cent) estimated by magnetic resonance soundings, which are known to slightly overestimate the specific yield in this geological context. The comparison of these two independent geophysical methods shows their potential to constrain the local hydrogeological parameters. Besides, this study evidences the worth of correcting the gravity signal for large‐scale hydrology before recovering local water storage parameters.