John Ruprecht

This is the first overview of stream salinity across the south-west of Western Australia since 1988. More than half of the rivers analysed in this study are now marginal in quality, brackish or saline, and only 44% of the south-west rivers are still fresh. Stream salinity was still rising at many of the sites analysed. Sixty-six percent of the analysed rivers had higher salinities in the last 10 years (1993–2002) than in the previous 10 (1983–92). Part of the reason for the higher salinity was lower rainfall over the last 10 years.

This report is an up-to-date, comprehensive review of stream salinisation arising from agricultural development of land in south-west Western Australia. The report starts with the history of salinity problems, going back to the earliest observations at the tum of the century. This is followed by a broad assessment of the current extent of stream salinisation. The next topic deals with causes of stream salinity, with a detailed discussion of the origin and distribution of salts and accumulation and leaching processes. The impacts of agricultural development on individual components of the water and salt cycles and at the regional scale are then reviewed. This leads to an analysis of stream salinity trends and predictions of future stream salinity. The final sections deal with salinty management practice and highlights future needs for both management and research.