Streambank erosion and instream sediment deposition are primary drivers of feshwater ecosystem health, particularly in large catchments where anthropogenically altered flow regimes have affected natural sediment transport dynamics. The Upper Murrumbidgee Catchment (UMC) is a prime example of this, where in-stream sediments continue to put pressure on stream health, exacerbated by upstream damming resulting in reduced the natural flow and transport of sediment through and out of the system. Invesitigating the sources of the sediment in key depositional areas, by identfying the contribution of sub-catchments in the system will be able to provide guidance for future land and water management strategies for a healthier catchment.
To achieve this, our study investigated the geochemical fingerprint of overbank sediments from 47 sites ranging from upstream tributaries to main channel locations in the catchment. Sediment samples were digested and measured using Inductively-Coupled Plasma Mass Spectrometry (ICP-MS), to obtain the concentrations of 28 elements. To identify a subset of elements for the discrimination of sediment sources, we applied a combination of univariate (Kruskal-Wallis) screening and multivariate stepwise discriminant analysis. This process highlighted a core set of elements as effective tracers of sub-catchment provenance.
The geochemical tracer set provides the foundation for ongoing work developping a sediment transport model for the UMC and applying mixing models to quantify the proportional contribution of individual tributaries to key instream depositional locations. This presentation will present our tracer selection framework and discuss emerging patterns in sub-catchment sediment contribution, with implications for targeted management in the UMC.