Keywords

Unconfined aquifer, Confined aquifer, Steady-state flow, Transient, Solute-transport model.

Location

Session D4: Water Resource Management and Planning - Modelling and Software for Improving Decisions and Engaging Stakeholders

Start Date

12-7-2016 9:10 AM

End Date

12-7-2016 9:30 AM

Abstract

The potentiometric surface in the Annaba basin, which covers an area of 264 km2, has declined significantly since 1995. A transient multilayer model has been developed to synthesise the hydrologic data. The groundwater flow was modelled using the finite difference method with a horizontal dimension of 500 x 500 m for the cells. The model consists of two layers, the first corresponding to the alluvial phreatic aquifer and the second to the deep confined aquifer, and is calibrated against the steady state groundwater heads recorded before 1996. Under steady-state conditions, the correspondence between simulated and observed water levels is generally good (average difference of 0.4 m). For the deep aquifer, the simulated time-series hydrographs closely much the recorded hydrographs for most of the observation wells. For the alluvial aquifer, the recorded hydrographs cover only a short time period, but they are reproduced. The model indicates that groundwater pumping induced a decrease in natural discharge, a downward leakage in most of the basin and a continual water-level decline. The model has also been applied to the analysis of recharge impact. Simulating the behaviour of the system over the period 1991-2009 without pumping indicated small changes in hydraulic head. These results show that the groundwater reservoir has a low recharge, but excellent hydraulic properties; A solute-transport model was used to study aquifer contamination from salty intrusion in coastal sectors; it was extended to the year 2030 by simulating an optimistic hypothesis that maintains present pumping until 2030.

 
Jul 12th, 9:10 AM Jul 12th, 9:30 AM

On the use of finite-difference model to evaluate the impact of underground water overexploitation

Session D4: Water Resource Management and Planning - Modelling and Software for Improving Decisions and Engaging Stakeholders

The potentiometric surface in the Annaba basin, which covers an area of 264 km2, has declined significantly since 1995. A transient multilayer model has been developed to synthesise the hydrologic data. The groundwater flow was modelled using the finite difference method with a horizontal dimension of 500 x 500 m for the cells. The model consists of two layers, the first corresponding to the alluvial phreatic aquifer and the second to the deep confined aquifer, and is calibrated against the steady state groundwater heads recorded before 1996. Under steady-state conditions, the correspondence between simulated and observed water levels is generally good (average difference of 0.4 m). For the deep aquifer, the simulated time-series hydrographs closely much the recorded hydrographs for most of the observation wells. For the alluvial aquifer, the recorded hydrographs cover only a short time period, but they are reproduced. The model indicates that groundwater pumping induced a decrease in natural discharge, a downward leakage in most of the basin and a continual water-level decline. The model has also been applied to the analysis of recharge impact. Simulating the behaviour of the system over the period 1991-2009 without pumping indicated small changes in hydraulic head. These results show that the groundwater reservoir has a low recharge, but excellent hydraulic properties; A solute-transport model was used to study aquifer contamination from salty intrusion in coastal sectors; it was extended to the year 2030 by simulating an optimistic hypothesis that maintains present pumping until 2030.