J. Olley et G. Caitcheon, Major element chemistry of sediments from the Darling-Barwon River and itstributaries: implications for sediment and phosphorus sources, HYDROL PROC, 14(7), 2000, pp. 1159-1175
In 1991, one of Australia's longest rivers, the Darling-Barwon, experienced
one of the world's largest recorded algal blooms. Nearly 1000 km of river
were affected. At the time of the bloom phosphorus originating from anthrop
ogenic sources was believed to be the principal cause. In this study we hav
e used major element chemistry to examine the sources of sediment and sedim
ent-associated phosphorus delivered to the Darling-Barwon River. We show th
at the sediments are derived primarily from the sedimentary and granitic be
drock areas of the catchment, not the intensively farmed basalt areas. We a
lso show that the sediment currently in transport in the Darling-Barwon doe
s not originate from contemporary upland erosion, but is probably derived f
rom lowland areas of the catchment that contain more weathered material. Ph
osphorus concentrations in the sediments are consistent with those in natur
al soils of the region, and evidence from two sediment cores indicates that
phosphorus concentrations have not changed significantly in the last 200 y
ears. The implications of these findings for algal growth control strategie
s are discussed. Copyright (C) 2000 John Wiley & Sons, Ltd.