| Vol. 19 (2000) | |||
- 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 (2000), 165 p., 64 Fig., 9 Tab.
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Abstract
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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