Delineation of the Hydrodynamic Interface Between Groundwater and Seawater in the Northern Part of the Coasts of Gulf of Aqaba Using Geoelectrical, Hydrogeochemichal and Hydrogeological Methods

Abstract

الملخص

تم إجراء مسح جيوفيزيائي كهربائي باستخدام طريقة سبر الأعماق (VES) لتحديد الحد الفاصل بين المياه الجوفية العذبة والمالحة في الجزء الشمالي من خليج العقبة، حيث تم عمل خمس مقاطع طوليه بعمق اختراق 70 مترا تقريبا. ولتأكيد النتائج الجيوفيزيائية، تم اخذ عدة عينات مياه جوفية من بعض الآبار الموجودة في المنطقة على أعماق مختلفة وتحليلها كيميائيا لمقارنتها بالنتائج الجيوفيزيائية . ولقد تم التوصل إلى أن عمق الحد الفاصل بين المياه العذبة والمالحة في منطقة الدراسة متغير حسب البعد عن الشاطئ ، حيث وجد العمق على بعد 100? 250 مترا عن الشاطئ 10?60 مترا على التوالي.

Abstract

The hydrodynamic interface between fresh groundwater and seawater in the northern part of the coasts of Gulf of Aqaba-Jordan was delineated using geoelectric sounding, where five vertical electric sounding profiles (VES) with penetration depths of around 70 meters were applied. To ensure the results some available shallow groundwater wells in the surrounding were measured and modeled on their water chemistry. From hydrogeologic aspects the shallow, fresh groundwater found in the unconfined clastics of granite origin forming coastal aquifer, show good responses to human impacts. When pumping rates exceeded the safe yield, encroachment of seawater towards the land was registered. On the other hand a type of encroachment (up-coning) was found, and was attributed to the intensive over-pumping in the area overlooking the northern part of the gulf. The results of all methods used; geoelectric, hydrochemistry and hydrogeology were in accordance with each other in revealing the hydrodynamic interface, and assisted in delineating it. This is in so far of importance because salt water encroachment not only destroy the fresh groundwater body, but may also negatively impact the self-purification of fresh groundwater body in near coast areas.