GROUNDWATER FLOW MODELING WITH PROCESSING MODFLOW FOR WINDOWS (PMWIN) FOR WATER BALANCE ASSESSMENT UNDER CLIMATE VARIABILITY IN THE KLELA BASIN, SOUTHERN MALI.

Abstract:

Groundwater resources are particularly important for the inhabitants of Klela Basin due to the absence of surface water especially during dry season (from November to May). Groundwater is the only permanent water resources. Therefore, a good knowledge of water balance may help for integrated water resources management. The current study was investigated on modeling of groundwater resources to establish water balance in order to evaluate the sources and sinks of groundwater system. The sandstone of Sikasso of the study area (3,680 Km²) was modeled using PMWIN model. The model grid was discretized into 239 columns, 256 rows making total grid cell number of 57,834, with a grid dimension of 300 m * 300 m taking into account of aquifer extension and hydrogeological data availability. Digital Elevation Modem (DEM) from Hydroshed was used to interpolate hydraulic head which was entered to the model as starting hydraulic head. The borehole logs data were used to estimate aquifer thickness. The model was calibrated, in steady-state and transient simulations, by trial and error`s estimation of hydrodynamic coefficients (hydraulic conductivity and specific yield) and the results were optimized using Parameter ESTimation (PEST) code in PMWIN. The results show that most of the water (99.9%) entering to the aquifer system is coming from infiltration local precipitation in the Basin. The stream leakage entering to groundwater was negligible (only 0.1%). However, the maximum water leaving the aquifer is coming from storage and stream leakage 67% and 33% respectively

Keywords: groundwater flow modeling, PMWIN, Klela Basin, DEM, water balance, climate variability.