Date of Award

6-2003

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Hydrology

First Advisor

Ibrahim Kocabas,

Second Advisor

Constantinos V. Chrysikopoulos

Third Advisor

Dr. Tareq AI-Zabt,

Abstract

Al Maqam-AI Saad area is located to the west of Al Ain city on Al Ain-Abu Dhabi Highway. This area was chosen to be studied because of the rapid decline of the water levels in the shallow aquifer as a result of continuous heavy withdrawal of the Ground water. In 1990-1991, the area was recognized as one of the major ground Water depressions in the Eastern Region where more than 40 meters of draw down Were noted in the center of depression. The objective of this study is to determine the Hydraulic status of the aquifer by means of characterization and to carry out a Quantitative assessment of the shallow aquifer in the study area.The characterization of the aquifer was conducted in order to assess the hydraulic conductivity in the area by means of re-analysis of previously conducted pumping tests.

Pumping tests conducted in the area by the Ground-water Research Program (GWRP)were reanalyzed using Aquifer Test Software. The results of the reanalysis are displayed in maps of transmissivity and hydraulic conductivity. The hydraulic conductivity in the area is small and ranges from 1 to 5 meters per day with increasing trend from east to west. This range of values is consistent with the heterogeneous lithology of the Aquifer that ranges from well sorted to poorly sorted gravel interblended with clay stone, silt lone, shale, and limestone. In addition to the pumping tests analysis,geological information and ground-water salinity distribution maps were also taken into on Ideation in the aquifer characterization and hence in the aquifer assessment.

The quantitative assessment was done by means of numerical modeling. The United State Geological Survey (USGS) ground-water model MODFLOW, was used to emulate the water level decline in the area and to show that the aquifer storage is being rapidly depleted. The model was calibrated to steady-state conditions by changing aquifer hydraulic properties and boundary conditions until the simulated water levels matched predevelopment \ after levels (before 1980). A transient calibration was achieved by reasonably matching the water levels produced from the transient simulation by those observed in the years 1990 and 1995.By 1997 most of the shallow aquifer in Al Saad area (the center of the cone of Depression) became dry; in addition, a new intensive agricultural development was initiated in the south and southwest of Al Saad area. Therefore a post-audit wasPerformed to the model in order to account for the new developments. The post-audit

Was calibrated to the water levels of 2003 in which a reasonable matching was obtained Between the simulated and the actual and water levels.Predictive model simulations for 2005 and 2015 were produced under the assumption That 2003 pumping rates would continue to the year 2015. The simulations indicated that By the year 2005, some wells will dry out and by 2015 a large portion of the shallow Aquifer in the study area will be dry. The model indicated that there are many Uncertainties in the available data and more data are needed in order to produce more3ensltJ e and refined model. This model can be used as a guide for future data collection activities and management tool for the water resources in the area provided that the uncertainties are taken into consideration.The main conclusion of this study is that the large drawdown occurs due to Combination of three factors: heavy ground-water extractions, little recharge, and low Conductivity. Thus, the following recommendations can be made in order to alleviate the exploitation of aquifer: Limit the abstraction rate by prioritizing its uses, regulate ground-water use, monitor and assess ground-water conditions, enhance the replenishment of ground water by developing the ground-water recharge facilities,

and minimize contamination of fresh water aquifer.

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