Estimation of suspended sediment loads in a seasonal stream in the wet-dry tropics, Northern Territory, Australia

One year of instantaneous suspended sediment concentration, C, and instantaneous discharge, Q, data collected at Ngarradj downstream of the Jabiluka mine site indicate that the use of a simple C-Q rating curve is not a reliable method for estimating suspended sediment loads from the Ngarradj catchment. The C-Q data are not only complicated by hysteresis effects within the rising and falling stages of individual events, but also by variable depletion of available suspended sediment through multipeaked runoff events. Parameter values were fitted to an event-based suspended sediment load-Q relationship as an alternative to the C-Q relationship. Total suspended sediment load and Q data for 10 observed events in the Ngarradj stream catchment were used to fit parameter values to a suspended sediment load-Q relationship, using (a) log-log regression and (b) iterative parameter fitting techniques. A more reliable and statistically significant prediction of suspended sediment load from the Ngarradj catchment is obtained using an event-based suspended sediment load-Q relationship. Fitting parameters to the event-based suspended sediment load-Q relationship using iterative techniques better predicts long-term suspended sediment loads compared with log-log regression techniques. Copyright (C) 2004 John Wiley Sons, Ltd.