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Fatma Abdullah Hamad Al-harthi

Estimations of aquifer properties from pumping tests in Muscat

Fatma Abdullah Hamad Al-harthi

Titre : Estimations of aquifer properties from pumping tests in Muscat Airport area

Auteur : Fatma Abdullah Hamad Al-harthi

Université de soutenance : Sultan Qaboos University

Grade : Master of Science (MS) 2020

Résumé partiel
Rising groundwater level has become a common problem in many regions worldwide, which happens due to natural phenomena and/or human activities. Groundwater flow modeling is one of the important tools required for implementing adaptation and mitigation measures for groundwater rising issue. Pumping test is commonly used for estimating aquifer properties such as hydraulic conductivity and specific yield required for groundwater flow simulation. When analyzing pumping test data, it is primly important to conceptualize the surrounding boundary conditions accurately. The main objective of this study is to analyze pumping test data obtained near an aquifer boundary in Muscat International Airport area using an appropriate simulation method to estimate aquifer properties. Secondly, it is expected to investigate the effect of aquifer boundary on the drawdown curve and variation of aquifer properties. This study used the data collected during a 24-hours long pumping test and 12-hours long recovery test near a stream (aquifer boundary) in the Muscat International Airport premises. Groundwater levels measured in the pumping well and in two monitoring wells, located at 15 m and 50 m away from the pumping well, were obtained. Firstly, pumping well data were analyzed under unconfined and transient flow conditions using Neuman’s (1975) analytical solution. AQTESOLVE program was used for matching Neuman’s theoretical curves with observed drawdown curves. Main aquifer properties such as transmissivity, anisotropy and specific yield were found with and without the aquifer boundary effect. Model results showed that the hydraulic conductivity and the anisotropy of the aquifer can be differ by 13% and 21%, respectively depend on decision to neglect the aquifer boundary. Secondly, a MODFLOW numerical model was developed to simulate the groundwater flow in the study area and compare observed and simulated drawdown data. Different conditions were simulated using aquifer properties found before. Model results indicated that the fraction of groundwater contribute from the aquifer boundary resulted to reduce the drawdown by about 26% near to the stream. Analysis of the numerical model under different conditions indicated that the hydraulic gradient has a significant effect on the accuracy of the simulated drawdowns. Therefore, the assumption of initial potentiometric surface has been horizontal, which was considered for deriving the analytical solution, would not be valid in the presence of strong hydraulic gradient. In such situations, it is recommended to use a numerical model.

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Page publiée le 4 mai 2021