A stocktake of the levels and sources of nitrate in groundwaters associated with sugarcane areas

Abstract

Water containing high concentrations of nitrate is unfit for human consumption and, if discharging to freshwater or marine habitats, can contribute to algal blooms and eutrophication. Previous studies have found elevated nitrate concentrations in groundwaters underlying sugar-growing areas, particularly the Bundaberg and Burdekin areas, and that in Bundaberg the problem was escalating. Nitrate pollution of groundwaters of the sugar industry is of particular concern because of the proximity of the industry to environmentally sensitive areas and the large number of people (in cities and rural areas) relying on groundwaters for drinking water. However, apart from recent studies in Bundaberg, data on nitrate in groundwater has generally come from inconsistent studies. These studies examining either a limited number of groundwater bores, or large databases of groundwater chemistry where sampling and analytical methods have been variable and, in some cases, inappropriate. So a reliable, consistent, industry-wide definition of the problem does not exist. This project determined the extent of nitrate contamination in groundwater underneath sugargrowing regions of eastern Australia, and examined the likely source of the nitrate. In bores where nitrate concentrations were elevated, and therefore likely to be a result of human activities, concentrations were monitored to provide an assessment of trends in nitrate concentrations. This information was used to promote “best management practices” through relevant extension, industry and regulatory groups, to restrict leaching of nitrate to groundwater.