SIMULATION OF REGIONAL FLOW AND SALINITY INTRUSION IN AN INTEGRATED STREAM-AQUIFER SYSTEM IN COASTAL REGION - SOUTHWEST REGION OF BANGLADESH

A numerical model for simulation of the regional flow and salt-water i ntrustion in an integrated stream-aquifer system in coastal regions is developed, considering the dynamic interaction between the streams an d the aquifer, The stream-aquifer model comprised of a two-dimensional depth-average finite-element model of the aquifer system and a quasi- steady node and reach model of the river network. The applicability of the model was demonstrated, through simulation of the spatial and tem poral distributions of flow and salinity in the estuaries and in the u nderlying aquifer of the Southwest Region of Bangladesh. The important management aspects of water transfer and additional pumping and their effects on the system were evaluated. The interactions between the st reams and the aquifer significantly influenced the flow and salt-water intrusion in the aquifer and the river network. An increased abstract ion of ground water in the area caused a significant increase in the e stuarine salinity. The salinity intrusion in the estuaries of the area , except in the southwest corner, could be reduced significantly by di verting the available water from the Ganges through the boundary river Gorai.