Groundwater storage evolution trend in a long-term (1960s-2020) mining area (Tim Mersoï basin, Niger): Highlight on the Tarat aquifer depletion in the Arlit region

The present study, as a first approach toward understanding a large scale aquifer depletion phenomenon in a practically unknown area, aims to evaluate the general trend of the groundwater storage of the Tim Mersoï basin (TMB), assess the magnitude of Tarat aquifer depletion in time due to uranium mining and highlight the need for a regional-scale study in the basin.

In arid and semi-arid areas, groundwater is considered the only plausible freshwater source. Increasing demand for water supply in such regions has increased groundwater use, leading to wide-scale depletion (Scanlon et al. 2006). Studies carried out worldwide showed that stresses on groundwater resources have increased under continual population growth and climatic variability.

For more than 50 years, the TMB has been the ultimate mining area in Niger. As we know, mining activities highly modify the stability of the groundwater scheme (Howladar 2013). Concerning groundwater depletion, mining activities have a key-role, being water-consuming and going deep with big aerial coverage. In the Arlit region, the Tarat aquifer, being the most productive, has been used for domestic uses and mining activities. Also, exploration permits delivered by the Ministry of Mines of Niger indicate a probable installation of new mining companies in the coming years (Kache 2014). However, no research has been carried out neither on the functioning of the hydrogeological system of the basin nor on the impact of the exploitation.

The activities in the TMB were listed for the past 50 years and the induced aquifer depletion was evaluated. Zoom was made on the Arlit region using in-situ data and direct field investigation to identify the evolution of the Tarat aquifer, from the 1960s to 2019.

This study shows that mining activities are the main water-consuming activity in the TMB and the regional groundwater storage is decreasing. In the Arlit region, the Tarat aquifer flow pattern was completely modified and had been depleted to more than 50m. To ensure groundwater resources and mining activities sustainability in the area a regional-scale study is highly needed.