Abstract:
: Located in northwestern Niger, the Tim Mersoï Basin (TMB) is an important mining region
in the scale of West Africa. Groundwater is considered the main source of fresh water in the basin,
especially for mining activities. It, therefore, appears essential to monitor their responses to these
activities. However, no study has been carried out in the Tim Mersoï Basin. This study aims to
evaluate the groundwater storage changes (GWSC) of the TMB and to analyze the spatio-temporal
evolution of the Tarat aquifer under the effect of mining activities in the Arlit region. For this
purpose, Gravity Recovery And Climate Experiment (GRACE), Global Land Data Assimilation
System (GLDAS), and in-situ data were used. The results show a variation of the GWS from 2002 to
2019 of about −0.1310 cm/year on the scale of the basin and −0.0109 cm/year in the Arlit mining
area. The GWSC at the basin scale and the one at the Arlit region scale were shown to be linked with
an RMSE between the two datasets of 0.79. This shows the potential of GRACE for contextualizing
studies in small areas. The study also highlighted that the groundwater flow direction was highly
modified; the drawdown of the Tarat water table was more than 50 m in the areas heavily impacted
by mining activities, with an increasing intensity from the northwest to the southeast of Arlit.
