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Sultan Qaboos University (2021)

Application of MODFLOW Numerical Model for Groundwater Management in Muscat Airport premises

Sakina Ahmed

Titre : Application of MODFLOW Numerical Model for Groundwater Management in Muscat Airport premises

Auteur : Sakina Ahmed

Université de soutenance : Sultan Qaboos University

Grade : Master of Science (MS) 2021

Résumé
Over the past decade, Muscat international airport area witnessed an alarming rise in groundwater levels. As a consequence, Oman Airports Management Company (OAMC) constructed a number of observation wells to monitor these levels. The objective of this study is to analyse the step-drawdown data collected during a pumping test in Muscat airport premises using analytical and numerical methods. The scope of this study is pumping well 7 (PW-7) which is surrounded by two constant head boundaries (Dirichlet boundary). The step-drawdown test is performed to estimate aquifer properties such as hydraulic conductivity, specific yield, and vertical anisotropy. These estimated properties were used to construct a 3D groundwater flow model using MODFLOW. The simulated head achieved a good fit to the observed heads with a RMSE of 0.052 m for PW-7. The numerical model addressed the limitation of the analytical model by identifying the effect of the nearby constant head boundary using the principle of superposition. The sensitivity analysis indicated that hydraulic conductivity has a higher impact on the model results. The uncertainty analysis showed that a ±5% uncertainty in the discharge rate will have no effect on the model results, whereas increasing Wadi water level will have a reducing effect on drawdowns. The tidal effect was also investigated and found to have no effect for distances larger than 500 m. To avoid land subsidence, the maximum amount of extraction corresponding to a 0.5 m drawdown was found using trial and error. Furthermore, it was found that any extension in the pumping duration will have no significant effect on drawdowns after two days. Finally, using the relationship between maximum drawdown and the pumping rate for MW-18, an equation was developed to identify the required amount of water extraction given a specified maximum drawdown

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Page publiée le 20 avril 2022