Water Journal : Water Journal April 2012
catchment management water APRIL 2012 117 Abstract The routine water quality monitoring programs undertaken by the Sydney Catchment Authority and Sydney Water Corporation contain some of the best long-term series of water data in NSW (and Australia). The data collected up until the present time represents not only a significant historical and ongoing investment, but a very valuable resource in terms of long-term information on water quality and quantity in the Hawkesbury- Nepean River catchments. State and trend analyses of the long-term data reveal a number of improvements in water quality in the Hawkesbury-Nepean River, but these are improvements from what was previously quite poor water quality in some areas and, for some analytes, water quality still has a long way to go before water quality objectives (e.g. ANZECC/ARMCANZ (2000) Guidelines) are met. There has been a significant reduction in flow over Penrith Weir (and at many other gauging stations in the catchment) in recent times, with current river flows being much less than the long-term average. This is a result of climate variability (lower rainfall in recent time periods), river regulation and water extraction. The long-term monitoring program represents a significant resource for investigating and interpreting the effects of both past and future NSW Government management decisions. Introduction Long-term monitoring programs are relatively rare in an Australian and worldwide context, but where they exist they provide many opportunities for understanding the current states and trends in the condition of a river system. They can also provide some very real challenges in terms of analysis and interpretation. The Hawkesbury- Nepean River is one of the most important river systems in NSW. Covering approximately 22,000 km2 (Figure 1), it is the largest river/estuary system in the Sydney Region and its complex ecosystems provide habitat for a multitude of native plant and animal species. Since European settlement it has been increasingly relied upon to meet the requirements of a burgeoning population and now provides 97% of fresh drinking water for more than 4.8 million people living in and around Sydney (Greening Australia, 2007). It also supports the agricultural industries that provide much of Sydney's fresh food, as well as supporting numerous other extractive, manufacturing and processing industries. In addition, the Hawkesbury-Nepean River is an important recreation and tourism destination. Regular water quality monitoring in the Hawkesbury-Nepean River system dates back to at least the 1940s when the CSIRO was undertaking regular water sampling measurements as far upstream as the Cataract and Cordeaux Rivers (Rochford, 1974). More recent water quality monitoring dates back to the late 1970s and early 1980s when concerns about sewage effluent disposal, urban expansion and extraction of sand and gravel in the river and on the floodplain were first emerging (National Trust of Australia, 1977). While there have been a number of shorter term studies of water quality in the Hawkesbury-Nepean (e.g. SPCC, 1983; EPA, 1994), the longest running ongoing monitoring program for water quality and quantity is the one currently operated by the Sydney Catchment Authority (SCA) and Sydney Water Corporation (SWC). Water quality monitoring for this program commenced in the early 1980s and now takes place at a number of sites along the length of the Hawkesbury-Nepean River, as well as at a number of important tributary sites. In addition to this monitoring, some local councils also conduct routine water quality monitoring within their respective council boundaries. The SCA/SWC long- term monitoring program data forms the basis of the current paper. Analysis of the long-term data series was undertaken in response to two major drivers: M Krogh A valuable resource for investigating and interpreting the effects of both past and future NSW Government management decisions HAWKESBURY-NEPEAN RIVER: LONG-TERM WATER QUALITY DATASETS Figure 1. Map of the Hawkesbury-Nepean River catchment.
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