HU - Hydrogeology and Environment

Journal of the Dept. of Hydrogeology and Environment, University of Würzburg (ISSN 09309-3757)

Editorial office: BGI, Greisingstr. 8, 97074 Würzburg, GERMANY

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Vol. 19 (2000)



Abstract



Vol. 19: 

Environmental Assessment and Optimization of Groundwater Resources Using Integrated Finite Element Flow and Solute Transport Modeling Combined with G.I.S. Technique.

Tareq Al-Zabet


Abstract:
Azraq basin supplies Amman with excellent water for drinking water purposes, but due to over-pumping from the Amman Water and Sewage Authority (AWSA) well-field, the water level dropped dramatically and signs of salination and depletion are starting to occur. The severe drawdown in the AWSA well-field caused a reverse in the hydraulic gradient and consequently, the saltwater in the center of the basin (Qa-Azraq) started to move in the direction of the well-field. In this study a coupled flow and solute transport models were constructed to analyze the size and behavior of the saltwater. The study showed that the saltwater was initially confined to the top Quaternary sediments in Qa-Azraq as it is bounded by horizontal and vertical barriers. The interface between freshwater/saltwater is transitional forming a mixing zone. The induced movement caused the saltwater to move horizontally in the beginning until it passed the vertical boundary fault and then tended to move vertically under the influence of its density. The saltwater completely extended vertically and tends at present time to flow horizontally in the direction of the well-field. The wells that are adjacent to the Qa-Azraq are showing a continuos increase in salinity. The model results indicate that if present abstraction rates continues (1998: 66 MCM/yr), the saltwater will continue moving. Expected arrival time to the AWSA well-field ranges between 500 - 2000 year. Pessimistic prediction scenarios showed that any increase in abstraction from the AWSA well-field or in the area north of the well-field, will cause severe drawdown and dryness of several wells in the springs area to the east and Azraq center. Optimistic scenarios showed that an abstraction quantity of 16 - 18 MCM/yr, is the appropriate safe yield of the Upper Aquifers System. The water injection simulations showed promising results and showed that it could be used as a replenishments method for the springs and the wetland. It could be also used as vertical boundary to prevent saltwater intrusion. Finally, any remedy measures in Azraq basin should be addressed as a part of larger comprehensive and integrated national policy framework.


Paper language: english




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