Watershed-specific model for streamflow, sediment, and metal transport

Metal transport for the Aberjona River watershed, a highly urbanized watershed located near Boston, Mass., is strongly influenced by different flow components. These flow components are characterized by different response times, sediment-transport characteristics, and metal concentrations. A series of box models was developed to determine the extent to which streamflow separation was capable of reproducing the observed variability in metal transport. The model includes subunits for sub-basins draining directly toward the Aberjona River, a sub-basin draining a major tributary, a ground-water withdrawal, and channels. The input to the model is precipitation; the outputs include streamflow, suspended sediment, and metal fluxes. For the sub-basins draining directly toward the Aberjona River, streamflow was modeled as the sum of three components: quick storm flow, slow storm flow, and long-term base flow. Sediment inputs were modeled in association with each streamflow component, and metal fluxes (dissolved and particulate) were modeled by assigning a metal concentration to each streamflow and sediment input. The model reproduced most of the variability in the measured data during calibration and verification phases and therefore illustrates that the separate streamflow components play a significant role in determining the total transport of contaminants by the Aberjona River.