Modelling study on environmental indicators in an estuary

Abstract

This paper reports on an investigation of the spatial and temporal variation of main environmental indicators in the Pearl River estuary using a numerical water quality model. An integrated field survey was undertaken in 2006 and 2007, and the data obtained were used to set up and verify the model. The water quality model was driven by a hydrodynamic model in which the monthly average freshwater discharges from eight major entrances were taken into account and the seaward boundary elevations were specified based on eight major tidal constituents. Two environmental indicators – dissolved inorganic nitrogen and chemical oxygen demand – were chosen as nutrient and pollution indicators, respectively, according to the actual pollution conditions. Both land-based sources (carried by the discharges) and air-based sources (wet and dry atmospheric depositions) were included in the water quality model and the processes of advection, diffusion and degradation were also modelled. The model predictions generally agreed well with the sampling data, and existing field and model results. The present contributions of the main sources were investigated and prospective scenarios of pollution reductions were predicted.