Hydrogeological characterization and hydrodynamic modeling of the Toudgha aquifer- Southeast Morocco

Résumé

The study area is located at the north-western limit of the Rheris basin in south-eastern Morocco, covered by the Toudgha oasis. The geology is characterized by a triple junction between the Central High Atlas in the North (Jurassic), the Pre-African Furrow (Cretaceous) in the middle and the Eastern Anti-Atlas in the South (Primary and Proterozoic), covered by Quaternary deposits. The underground water resources are distributed according to the geological structures in an interdependent aquifer system, while the surface water resources essentially come from Jurassic and Cretaceous springs in addition to the inflow of the Toudgha river. The climate is arid, marked by low and irregular rainfall, in space and time, with significant temperature fluctuations. The aim of this study is firstly to carry out an updated hydrogeological synthesis of the Toudgha aquifer and secondly to analyze the potential effects of the construction of the Tametatoucht dam upstream on the aquifers supply. Several geological, hydrogeological, hydro-climatic and hydrodynamic data have been collected and analyzed in order to spatialize the data and to improve the characterization of the groundwater boundary conditions, we have used the Geographic Information System tool. Finally, a computer code is established for the hydrodynamic simulation. The hydrogeological synthesis indicates that the groundwater balance is negative. The use of a digital model has allowed to simulate the aquifer status by parameterizing the contribution of the groundwater exploitation at different horizons as well as the contribution of the Tamtatouch dam. The findings show that the dam can guarantee the preservation of the aquifer water level considering normal water withdrawals, however, during a 25-year period there is a significant reduction.