Quality simulation along river systems (QUASAR): model theory and development

A combined flow and process based river quality model is described for a range of water quality determinands including nitrate, dissolved oxygen (DO), biochemical oxygen demand (BOD), ammonium ion, temperature, pH and a ‘conservative’ water quality determinand. The model theory and development, data requirements and operational modes are described and a brief history of the use and applications of this model given. The model is designed to assist in the management of medium to large river basins.