Brodie et al., 2008: 

"Recent research has allowed us to more clearly identify and quantify the losses of suspended sediments, nutrients and pesticides from different land uses and land management practices. Very strong relationships between fertilised land uses (sugarcane, banana) and in particular loss of nitrate (and sometimes ammonia) have been shown in the Tully basin (Mitchell et al. 2006; Faithful et al. 2007). This relationship is illustrated in Figure 4, where the relationship between fertiliser-additive land use and average nitrate concentrations has been plotted (Mitchell et al. 2006), and also in the boxplots from the Tully and Mackay-Whitsunday regions that show average nitrate and nitrite concentrations for sugarcane sub-catchments compared to other land uses within these two regions (Figures 5 and 6) (Rohde et al. 2006a; Faithful et al. 2007). This relationship has also been shown in the Russell-Mulgrave catchment (Connolly et al. In prep), Lower Burdekin (Bainbridge et al. 2006b) and Mackay-Whitsunday catchments (Rohde et al. 2006a). The loss of herbicide residues – particularly diuron, atrazine, hexazinone and ametryn – from sugarcane cultivation has been firmly established (Packett et al. 2005; Rohde et al. 2006a; Faithful et al. 2007; Lewis et al. 2007a; Stork et al. 2007) in the dominant sugarcane regions from Bundaberg to Tully. In contrast losses of suspended sediment from sugarcane cultivation has been shown to be relatively low, reflecting fifteen years of improved soil conservation measures including green cane harvesting, trash blanketing and reduced tillage (Rayment 2003; McJannet et al. 2005; Bainbridge et al. 2006b; Rohde et al. 2006a; Faithful et al. 2007). However, there is still some evidence of elevated erosion in sugarcane cultivation areas compared to forested areas as shown from the results of Hateley (2007), who identified the sources of sediments collected from waterways draining different land uses within the Tully River catchment. In contrast, rangeland beef grazing lands lose large quantities of suspended sediment through erosion associated with low vegetation cover (Brodie et al. 2003; McKergow et al. 2005a; O’Reagain et al. 2005; Bainbridge et al. 2006a; 2006b; Bartley et al. 2006; Dougall et al. 2006; Fentie et al. 2006). However, the likely improvements in suspended sediment conditions due to better vegetation (pastures and trees) management are not well quantified (Coughlin et al. 2006; Gordon and Nelson submitted).

This research has also highlighted the difference in the pollutants of concern between the wet and dry catchments within the GBRCA. Due to the wetter climates and presence of intensive agricultural land uses (sugar cane and horticulture) and their associated fertiliser and pesticide usage, the Wet Tropics and Mackay-Whitsunday areas have been identified as regions of high nutrient and pesticide runoff concern (Furnas 2003; Fabricius et al. 2005; DeVantier et al. 2006). Whilst the significantly larger Fitzroy and Burdekin River catchments (each ~135 000 km2), dominated by unimproved savannah / woodland rangeland grazing, are identified as considerable contributors of suspended sediment to the GBR lagoon (Mitchell and Furnas 2001; Furnas 2003; O’Reagain et al. 2005; Bainbridge et al. 2006b; Packett 2007; Waters and Packett 2007)."

 AND

"Urban development

The hardening of the landscape with buildings, roads, car parks and their accompanying drainage works leads to major changes in flow regime that cause much more rapid runoff and more peaked flows in waterways. Urban stormwater is typically of poor quality and the first-flush effect is particularly pronounced in hardened catchments in which runoff from the first rains after a dry spell carries a very high proportion of catchment contaminants. More prolonged rain usually provides dilution and improved runoff quality, unless it is sufficiently intense and causes flooding, in which case water quality can suddenly become poor again due to accelerated erosion and failure of effluent and waste containment systems (e.g. sewage overflows). Such flows deliver a range of contaminants into waterways, including many chemicals from transportation and small industry, nutrients and pesticides from parks and gardens, metals from galvanised roofing, and general rubbish. The major potential point source of pollution in waterways is sewage treatment plants that can deliver an effluent that is rich in organic matter and nutrients. Impacts on waterways include the boosting of microbial and weed growth as well as hypoxia. There is no recent published information on the impacts of urban development in the GBR catchment, although anecdotal evidence suggests that poor control of new development works has led to substantial land erosion and contamination of waterways by sediments in the Cairns and Townsville regions."

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Citation and/or URL

Brodie, J., Pearson, R., Lewis, S., Bainbridge, Z., Waterhouse, J. & Prange, J. 2009, Water quality research: baseline synthesis and year 1 summary: a report to the Marine and Tropical Sciences Research Facility (MTSRF). Reef and Rainforest Research Centre Limited, Cairns, Australia 

Spatial Coverage

Mackay-Whitsunday

Temporal Coverage

2004-05

Update Frequency

Not applicable 

Other Information

None