Behaviour of the dilution characteristics of the coastal waters off Tuticorin is presented in the background of setting up of a desalination plant. Simulations of dispersion and spreading of the proposed discharges has been carried out. Scenarios of dilutions were assessed based on the results of a 2D model using the advection-dispersion theory. It is observed that under prevailing currents in the region, the dispersion of the discharge will be advected away as a combined plume. Ambient conditions are found achieved in close proximity zones within the discharge location and thus there will not be any changes in the water quality in the adjacent coastal waters. Model validation results showed that the values are well in agreement with the observed values. It is suggested that the offshore waters at a distance of 2 Km away from the coastline could be considered as optimum where the environmental impact on the ecosystem due to the disposal operations is considered to be minimum