Numerical modelling study of seawater intrusion in Indus River Estuary, Pakistan

Seawater intrusion is one of the major problems in the Indus River Estuary (IRE), Pakistan. A FVCOM-based numerical model was constructed to study the seasonal variability of currents and salinity in the IRE. The model was well calibrated with observed water level, current velocity and salinity data. Model results indicate that current velocity in dry seasons is smaller than that in wet seasons. Salt-water intrudes far upstream for about 65 km. In flood seasons, freshwater discharge is the main component controlling currents and saltwater intrusion in the IRE. Currents are all seaward during both the flood and ebb phases. Saltwater-freshwater interface is pushed seaward to the mouth of the estuary. Both field data and numerical results reveal that stratification (mixing) occur at the mouth of the IRE during wet (dry) seasons, dominated by estuarine circulation and tidal straining.