Sedimentation in Lake Albert, Wagga Wagga, NSW

A sedimentation study of Lake Albert, a small lake artificially created at the turn of the cenmry, was conducted to determine the amount, rates of accumulation and sources of sediment in the lake. A series of diversions of near by creeks has resulted in the accumulation of relatively complex deltaic sequences adjacent to the diversion outfalls. Sediment now fills approximately 9% of the original volume of the lake basin. At the present rate of sediment accumulation the lake may be significantly filled in about 600 years, although this projection will be modified by climatic and catchment related factors during that time. Stratigraphie, mineral magnetic and radionuclide techniques were used to demonstrate that a rapid and sustained transition in source composition had occurred on the principal delta. ^^^Cs data and historical evidence indicated that this event occurred in the early 1960\u27s. The post-transition sediments were traced to a local source, namely a large erosion gully which had formed in the adjacent diversion channel. Radionuclide results showed that the most likely source of pre-transition sediments was stream channel bank alluvium. A relatively minor amount of sediment derived from topsoil was also detected in the pre-transition sediments. Measurements of naturally occurring radionuclides in channel sediments at the first confluence of one of the major lake tributaries clearly showed that sediments fi-om the two contributing subcatchments are distinguishable. The spatial and temporal continuity of channel sediment composition was demonstrated, proving the applicability of this technique to sediment tracing studies