Abstract Title: Modelling of Groundwater Dynamics Using Visual Modflow in the Koda Catchment, Mali

Abstract Submitted to: HYDROLOGY

Abstract Text:

Groundwater is the only permanent source of water present in the Koda catchment, which occupies a surface area of 4921 km2. Surface water appears during the rainy season and dries some few months after this season. Groundwater resources are used for all the water need of the inhabitants of the Koda catchment, therefore, a good knowledge of the dynamics of the groundwater flow is required for well manage these resources. Watershed-scale groundwater flow models are developed in order to understand the behavior of the aquifer system. In the current study, the groundwater flow model Visual Modflow was used to simulate the dynamics of groundwater flow in the Koda catchment. Hydrogeological, geological, topographical, climatological data collected from historical and current field data were used as model inputs. Another most important input parameter of the model is groundwater recharge, which was estimated applying the lumped Gardenia model in the study area and obtained 20% of annual precipitation as the recharge value. The Visual Modflow model domain was discretized into grid (50 columns, 50 rows) with a total grid cell number of 2500 with a grid dimension 300m *300 m. Digital Elevation Model (DEM) from Hydroshed was used to interpolate hydraulic head through the study catchment scale, which was entered to the model as starting hydraulic head.
The Precambrian sandstones aquifer in the study area was simulated under steady state condition. After development and calibration of the model using trial and error’s estimation of hydraulic head, the correlation coefficient was 0.98 with 4.84 m and 6.05 % as Root Mean Square and Normalized RMS respectively while the Standard Error of the Estimate was 1.19m. The results showed the great fit between measured and calculated water levels. In Conclusion, the Visual Modflow model can be used to simulate the underground water level in the research area.
Keywords: Groundwater dynamics, GARDENIA Model, Visual Modflow, DEM, Koda Catchment, Southern Mali.