A NUMERICAL GROUNDWATER FLOW MODEL OF WADI SAMAIL CATCHMENT USING MODFLOW SOFTWARE

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The climate in most of Gulf Cooperation Council (GCC) countries is considered arid with limited water resources. Proper management of scarce water resources is therefore necessary for sustainable water supply while meeting the growing water demands. A three-dimensional finite-difference groundwater flow model of Wadi Samail Catchment was developed to simulate groundwater flow and to evaluate the sensitivity of the model to the varying of input parameters. Model inputs include lithology of the aquifer derived from borehole data, observed groundwater levels, rainfall, and initial hydraulic conductivity values from pumping tests. The aquifer was divided into four layers. The steady-state calibration was carried out using data in 14 monitoring wells in July 2016. The hydraulic conductivity (k) and recharge values were calibrated using observed groundwater levels with the estimated root mean squared error (RMSE) of 0.8m. The estimated parameters were verified with groundwater levels in October 2016. The RMSE between observed and simulated water levels was 0.81m. The calibrated model was then used to assess the sensitivity of the model to the changes in pumping rate, hydraulic conductivity (k), and recharge. Results showed that the water levels were most sensitive to the changes in hydraulic conductivity of the first layer. While pumping rates and recharge were less sensitive compared to the hydraulic conductivity. In conclusion, the sensitivity analysis results can be used as a management tool for sustainable water resources.