Document

Numerical modeling of groundwater flow and nitrate in Wadi AL-Khoudh watershed using MODFLOW and MT3DMS.

Publisher
Sultan Qaboos University.
Gregorian
2023
Language
English
English abstract
Al-Khoudh well-field is considered as one of the most essential groundwater resources for Muscat Governorate. Currently, there are more than 61 pumping wells in operation within this well-field area, clustered around the Al-Khoudh recharge dam, which is accounting for about 50,000 m3 of water volume pumped every day. In recent years, population density in the surrounding area of the well-field is increasing at an unprecedented rate. Thus, increasing water abstraction and deterioration in groundwater quality has posed a threat to the sustainability of this well-field. In this study, different scenarios were simulated to understand the aquifer response to varying rates of water abstraction in addition to the impacts of urbanization in terms of practices at surrounding residential areas and cultivated lands. Two models were utilized in this study, namely MODFLOW and MT3DMS. The Transient State MODFLOW was used to simulate groundwater flow for a period of 22 years (2018-2040). The simulation results showed that the overall mean water levels of all observation wells will be reduced by 2.896 m at July, 2040. In the increased abstraction scenario of 10%, 20% and 30%, the results have indicated that the overall mean water levels have decreased by 0.657 m, 1.313 m and 1.617 m, respectively. Similarly, the water abstraction was reduced with various percentages of 10%, 20% and 30%, in which the results showed that the overall mean water levels will be increased by 0.64 m, 1.283 m and 1.921 m, respectively. For the increased recharge scenario of 10%, 20% and 30%, the overall mean water levels have increased by 0.04 m, 0.079 m and 0.119 m, respectively, while in the reduced recharge scenario by 10%, 20% and 30%, the mean water levels have decreased by 0.043 m, 0.085 m and 0.128 m, respectively. In the flash flood scenario, the overall water levels of all observation wells have increased by 0.00606 m. MT3DMS model was utilized for simulation of Nitrate transport and concentration calculation in the study area. It was found that the maximum and minimum concentrations of Nitrate at December, 2040 will be 26.4803 mg/L and 0.0038 mg/L, respectively. The various simulated scenarios in this study have elaborated the impacts associated with extensive water abstractions as well as impacts of increasing urbanization. The findings of this study can assist the decision makers to initiate the suitable remedial counter measures which can mitigate the impacts of the increased water abstraction and Nitrate discharge.
Arabic abstract
يعتبرحقل آبار الخوض من أهم مصادر المياه الجوفية لمحافظة مسقط. يوجد حالي 61 ضخ قيد التشغيل داخل ًمنطقة حقل الآبار هذه، متوزعة حول سد وادي الخوض، والذي يعد مسؤولا عن ضخ حوالي 50000 مترا مكعبا يوميا من المياه في السنوات الأخيرة ،ازدادت الكثافة السكانية في المنطقة المحيطة بحقل الآبار بمعدل غير مسبوق . وبالتالي فإن زيادة ضخ المياه الجوفية وتدهور جودتها ا قد شكل تهديد لاستدامة حقل الآبار بمنطقة الخوض.
Category
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Al-Hadhramiyah, Asma Talib.
Sultan Qaboos University.
2022