Sustainable restoration of endangered coastal ecosystems is today of great environmental interest and scientific value. Among the coastal ecosystems, the lagoon shows a wide range of geographical and ecological variation. The Chilika Lagoon a Ramsar Site of international importance and the largest brackish water lagoon in Indian sub-continent is one of the finest repositories of aquatic biodiversity and a source of fishery, sustaining the livelihood and nutritional need of about 0.2 million local fisherfolk. Sedimentation, from riverine discharge and disintegration of macrophytes, choking of the outer channel, shifting of the inlet mouth, decline in water area and increase in vegetated area, and the opening of new inlets are the dominant processes influencing the cotemporary phase of lagoon transformation in the Chilika. Circulation, fate and transport of nutrients are the critical component in determining the lagoon ecosystem. The present study discusses a water quality model coupled with a hydrodynamic and advection-dispersion model to describe the important physical, chemical and biological processes. The hydrodynamic and advection-dispersion model simulates the flow forcing, transport, mixing and dispersion of water quality concentration at different spatio-temporal scales. Bed resistance coefficient, the eddy viscosity coefficient (Smagorinsky formulation) and the wind friction coefficient in hydrodynamic model, heat exchange coefficients and dispersion coefficients in advection/dispersion (AD) model are the major calibration factors. The water quality model includes physical processes (reaeration, settling), biochemical processes (adsorption, transformation) and biological processes (organic degradation, primary production). Different rate constants have been calibrated with several sensitivity analyses to obtain an optimized validation. Skill test analysis of temperature (r(2)=0.77), salinity (r(2)=0.68), DO (r(2)=0.52) and nutrients proves the potential of the model to simulate water quality at different spatio-temporal scales. The model can act as an excellent tool to simulate water quality and prediction of futuristic scenarios. (C) 2015 The Authors. Published by Elsevier Ltd.
