『Abstract
　Relative contribution of different diffuse sources to the sediment and phosphorus (P) budgets in the Ben Chifley Reservoir was estimated using a multivariate mixing model and geochemical indices and tracers. The influence of the underlying geology on land use characteristics and the dynamics of sediment and P in the catchment were discussed. Sediments currently in transport to the reservoir are derived mainly from areas underlain by Quaternary alluvium, accounting for 33％ of the reservoir sediment budget. A major portion of the sediments from the Quaternary alluvium originates from pasture land which also contributes about 60％ of sediment-bound P in the reservoir, followed by cropland (30％) and forest area (10％). Phosphorus-based fertiliser contributes more than 50％ of the soil P in pasture and cropland and more than 60％ in forest plantation area. The remaining P reaching the reservoir originates from natural soils (native sources). Phosphate from both fertiliser and native sources are transported to the water courses and ultimately the reservoir as a consequence of gully, stream bank and surface erosion. Erosion control, trapping of fertiliser runoff, establishing riparian vegetation and reducing application of P-based fertiliser by increasing native pasture cultivation in the risk areas should be considered as management options for controlling the impact of P and sediment in the reservoir.

Keywords: Catchment management; Eutrophication; Sediment, nutrients, reservoir; Water quality』

Introduction
Materials and methods
　Study site
　Sample collection
　Geochemical analysis
　Source identification of sediments and P
　Contribution of chemical fertiliser to soil P
Results 　
　Geochemistry: elemental composition
　Potential sources of sediment
　　Quaternary alluvium LG unit
　　Basaltic LG unit
　　Granitic LG unit
　　Sedimentary and metasediments LG unit
　Potential sources of phosphorus
Discussion
Conclusions
References