Simulation of flow regime of dibdibba dandy aquifer in Safwan-Zubair Area, South of Iraq

Abstract EN

A two-dimensional model is constructed to simulate the flow regime of the upper part of Dibdibba sandy aquifer in Safwan-Zubair area, south of Iraq.

Although the Dibdibba Formation is a multi-layer system in the surveyed area, the suggested conceptual model which is advocated to simulate the flow regime of aquifer is fixed for one layer, i.

e., the activity of the deeper aquifer is negligible.

The model is calibrated using trial and error procedure in two stages: steady state followed by transient state.

The outcome of the calibration process demonstrated considerable spatial variations in transmissivities and storativites of the aquifer system.

A very good similarity between the observed and simulated groundwater levels in the steady state calibration is observed.

A reasonable representation of the hydraulic gradient over the mode area which consistent with relative magnitude of hydraulic conductivies is obtained during this calibration stage.

Transient calibration is undertaken to calibrate the aquifer storage parameter after the steady state calibration is achieved.

The transient calibration results are evaluated by comparing water levels at eight observation wells.

Good matches are observed for all cases.

The reliabilities of calibrated parameters are checked through sensitivity analysis.

Verification test is also added to ensure that the calibrated model could be an adequate counterpart of the actual groundwater system and to verify the reliability of the model results.

The model is verified against the measured heads during June 2000.

The verified model is utilized to predict behaviour of the aquifer over a planning horizon of 10 years (2000-2010) under two developments scenarios.

The management plans are undertaken with continuity of existing trend of growth of pumping wells, i.e., 200 wells per year and without growth and still the situation is similar to that in year 2000.

The first run indicates that the decline of groundwater heads of about one meter in the central part of the area and of about 0.5 meter in the northern and western parts is expected.

The outcome of the second run demonstrates that no significant changes from 2000 status have occured.

The calibrated model can be used, if necessary data is available, to establish the responses of the aquifer to artificial recharge which is suggested to enhance the water availability and rebalance the aquifer in other context.