Development of Estimation Methods for Tributary Loading Rates of Toxic Chemicals

摘要

Tributary loading estimation methods were evaluated by conducting retrospective studies with comprehensive sets of field data for flow rates, suspended solids, nutrients, heavy metals, and polychlorinated biphenyls (PCBs) from two different rivers. Three broad classes of leading estimation methods were investigated: simple averaging methods, ratio estimation methods, and regression methods. Estimators were evaluated using Monte Carlo sampling studies in which random subsamples of complete loading records were used to estimate annual loadings. These estimates were then compared to 'true' loadings determined by calculations using the entire record. No single estimation approach was found to be superior for all of the constituents and hydrologic conditions tested.