Development and evaluation of a mathematical model for the study of sediment-related water quality issues

A mathematical model (Sediment-Transport-Associated Nutrient Dynamics - STA ND) has been developed for the study of sediment-associated water quality i ssues. The model is intended to simulate changes of water composition assoc iated with sediment behavior. It has a 3-level structure. The first level a ccounts for the hydraulics of open-channel flow. The second computes sedime nt transport potential and actual rates based on the information provided b y the first level. A non-equilibrium approach is used. In the third level, changes of nutrient concentrations along a studied river are computed with the consideration of nutrient transport, adsorption/desorption, and release . In order to calibrate the model, field data were collected from the Ocone e River, a major tributary of the Altamaha River in Georgia, USA. Two stati ons, approximately 17 km distant from each other, were established along th e river for the purpose of data collection. Observations of the river's hyd raulics, suspended sediment, and water quality (mainly orthophosphate, nitr ate, temperature, specific conductivity, oxidation-reduction potential, dis solved oxygen, and pH) were collected at the two stations. Another data set collected along a major tributary of the Yellow River in China was also us ed for calibration of the model's hydraulics and sediment transport parts. Calibration and validation results are encouraging, which suggests STAND ma y be a useful tool for the thorough study and understanding of nutrient dyn amics associated with sediment behaviour.