Where we are now

The current condition of the region’s water and land resources, and draft Environmental Values of water for each of the Burdekin WQIP region’s 48 subcatchments and 6 basins is summarised within the Burdekin WQIP Catchment Atlas. This chapter introduces the Catchment Atlas and how to navigate around it. The figures in section 7.1 illustrate the layout of data and information that is synthesised within the Atlas for all the basins and subcatchments. The Burdekin WQIP Catchment Atlas is found on the accompanying CD.

The whole-of-Burdekin WQIP region resource condition is summarised in section 7.2, while overviews of other related aspects such as climate, geology, landscape, soils, bioregions, river discharge, people and livelihoods are presented in Chapter 2. Land and water resource condition issues and threats are reviewed in Chapter 3.

The condition of riparian habitat is reported to have declined over the last 30 years in most of the Burdekin WQIP subcatchments and currently varies greatly between basins and subcatchments. In particular, significant deterioration is evident in the Cape Campaspe, Belyando and Suttor Basins since the 1970s. Relatively little is known about the diversity and condition of aquatic habitats in the Belyando and Suttor Basins, while these two basins also display the greatest decline in ecosystem services over the last 30 years as a result of riparian clearing. In contrast, the Upper and Lower Burdekin, and Bowen Broken Bogie Basins, where large permanent wetlands and waterholes, and perennially flowing rivers and streams are quite common, display the greatest diversity and ecological value of aquatic habitats.

Based on modelling of soil erosion and water quality by the CSIRO, the Upper Burdekin Basin stands out with respect to the total loss of soil from erosion, largely as a consequence of its significant area, high rainfall, steep topography and erodible soils. However, high rates of soil erosion (soil loss per hectare) are identified from many subcatchments within the Upper and Lower Burdekin Basins and, in particular, the Bowen Broken Bogie Basin where the erosion rates are well above the Burdekin WQIP region average in several subcatchments.

The sediment and nutrient contribution to end-of- Burdekin catchment loads from the Bowen Broken Bogie and Lower Burdekin Basins, which lie below the Burdekin Falls Dam (BFD), is substantially greater than reflected by total soil loss values within basins because of dam trapping. That is, trapping of sediment and nutrient originating from basins above the Burdekin Falls Dam (BFD) reduces their contribution significantly to end- of-Burdekin catchment loads. The trapping efficiency of the BFD can be highly variable from year to year; it was calculated from water quality monitoring data to be 88%, 62% and 59% over the 2005-06, 2006-07 and 2007-08 wet seasons respectively.

Field surveys and analyses of ground cover from satellite imagery show that this indicator of soil condition and vulnerability to soil erosion varies markedly at all spatial scales, as well as between years and, in particular, over cycles related to wet and dry conditions within the region. Nevertheless, there are discernable areas where the density of marginal and degrading ‘D’ condition land is particularly high, notably in the Belyando and Suttor Basins.

Water quality monitoring of wet season flows over the five year period from 2002-03 to 2006-07 within the Burdekin WQIP region has determined that in-stream water quality is most significantly degraded in parts of the Bowen Broken Bogie, Upper Burdekin and Belyando Basins. Water quality monitoring data show the highest concentrations of suspended sediment to be in the Bowen Broken sub-basin.

A disproportionately high sediment contribution to the end-of-Burdekin catchment load comes from the Bowen Broken Bogie Basin and other below-dam subcatchments. There is general agreement between monitored water quality data and the results of SedNet modelling with regard to the major source areas of suspended sediment and particulate nutrients.

The hydrology of the Lower Burdekin irrigated cropping area is characterised by surface waters that, mostly, drain away from the elevated levee banks of the Burdekin River into a large number of rivers and creeks that flow directly into Bowling Green and Upstart Bays. Nutrient concentrations, mostly as dissolved inorganic nitrogen (nitrate, nitrite and ammonia or DIN) in surface water discharge from the Lower Burdekin irrigated cropping area are greatly affected by fertiliser-additive land use, which is dominated by sugar cane. However, deep drainage of DIN to the underlying aquifer is understood to account for a very significant proportion of the total DIN load to coastal waters. A suite of herbicides has also been commonly detected in the waterways of the lower Burdekin.

Based on a review of the current resource condition of the Burdekin WQIP region, the following priority subcatchments are identified for grazing and sugar interventions:

Grazing lands

• Bogie River
• Bowen River
• Little Bowen River 
• Pelican Creek
• Burdekin River (below dam)
• Burdekin River (above dam)
• Burdekin River (Blue Range)
• Clarke River

Irrigated cropping (sugar) lands

• Barratta Creek
• Burdekin Delta
• Haughton River
• Landers Creek
• Upstart Bay