Surface water quality - 2006Home | Water | Water Quality & Ecology | Surface Water Quality | 2006 Surface water monitoring carried out in ShoalhavenCouncil has divided the city into 20 separate catchments for the purposes of surface water quality testing and each quarter a number of sites in each catchment are tested for various pollution parameters. The catchments are tested quarterly for “routine” physico-chemical parameters (dissolved oxygen, pH, conductivity, salinity and temperature) as well as for faecal coliforms. Additionally, selected sites in each catchment are tested for nutrients (nitrogen and phosphorous) and chlorophyll-a. Chlorophyll is the green pigment on plants (including algae) and thus measuring chlorophyll gives an indirect measure of algal growth. Each of the parameters tested provides information on a specific aspect of the water or catchment. When a number of these parameters are combined it can be seen that they are inter-related and provide an overall picture of the water quality at a particular site on a particular day. By testing at a number of sites at regular intervals, Council is gaining an important insight into trends and issues in each of the major catchments. During 2005/06 more than 400 samples were collected approximately 5,200 tests were performed. The water monitoring program was altered during 2005/06 with each catchment sampled less frequently, that is a minimum of twice a year instead of a minimum of four times a year. This allowed Council to conduct more tests at all sample sites such as nutrient levels and to include additional tests such as suspended solids. The change in the program also allowed council to direct more effort into sampling certain catchments more frequently where more information was required. Increased sampling frequency and sampling of rainfall events was conducted at Millards Creek in conjunction with a University of Wollongong project. See University Projects for more information. Details of results and specific actions in the catchments are outlined in the following catchments reports. Water Quality Index Not all parameters tested are reported in the catchment reports as examining water quality can be quite complex. In a bid to simplify this, Shoalhaven has adopted a water quality index that was originally developed for the “Streamwatch program”. Council has attempted to adapt this index based on local experience and for the parameters tested locally in estuarine environments. This involves determining a value from the individual result of ph, faecal coliforms, dissolved oxygen, total nitrogen, total phosphorus and chlorophyll a and then multiplying it by a predetermined weighting. All the results are then added to give an overall water quality index. The method provides a snapshot view of catchment water quality, however, it is not a precise representation.
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