WATER QUALITY OF THE INFLOWS/OUTFLOWS OF THE BARRATTA CREEK SYSTEM

NUMEROUS recent investigations/reports have identified agricultural production as a source of potential environmental problems for the GBR. The Productivity Commission reported that 'soil erosion and runoff of fertilisers and chemicals pose a significant threat to the Great Barrier Reef (GBR), particularly the inner reefs'. As the Barratta Creek system is a major drainage line for much of the Burdekin River Irrigation Area (BRIA) developed since 1988, this study builds on data already available for this system, by expanding the parameters measured and the frequency of measurement, and provides information to allow better interpretation of indices of water quality and stream health and their changes over time since the irrigation scheme commenced. Data for inflow to and outflow from each of the Barratta Creek sub-catchments were collected for a range of pesticides, nutrients and other important environmental parameters and compared with those just after the scheme was established. The data showed there has been no rise of consequence in the salinity, nutrient levels or turbidity of the flow compared with previous studies 10-12 years ago, during the early stages of development of the BRIA. There appeared to be some slight improvement in the nutrient status of the outflow and the dissolved oxygen status remained at healthy values. The importance of the quality of the inflow water on outflow water quality was evident. With the exception of diuron, pesticides measured remained at levels which posed no significant environmental concern. Diuron levels were elevated and fluctuated sharply during the high-intensity weed control period but fell rapidly thereafter. The brief presence of diuron and hexazinone in inflow water suggested individual case(s) of poor farm practice. The occurrence of a 'wet season' event on concentration of all measured parameters was highlighted.