Belyando River Basin
Belyando Basin is comprised of 7 sub-catchments, as follows:
SedNet Modelling of Water Quality
Model results for the Upper Burdekin Basin are summarized as follows:
- Basin modelled area: 35,030 sq. km.
- Source contributions: Hillslope = 66%; Gully = 21%; Streambank = 13%
- Total suspended sediment (flow weighted) supply: 1,182.5 kt/yr
- Total suspended sediment supply (flow weighted; normalized to area): 338 kg/ha/yr
- Suspended sediment end-of-basin (flow weighted) yield: 1,063.7 kt/yr
- Event Mean Concentration (flow weighted): 573.5 mg/L
- Mean Annual Flow: 1,854,892 ML
Hillslope erosion is identified as the major source of sediment and particulate nutrients affecting water quality in the Belyando Basin (66%), although gully (21%) and streambank (13%) erosion are also predicted to be significant contributors. Loss of sediment and associated particulate nutrients from all sources (supply) is moderately high (1,182 kt/yr) because of the very large (modelled) area of the Belyando Basin (35,030 sq km). This loss equates to 338 kg/ha/yr, which is quite low when compared to all subcatchments and other basins.
Modelled suspended sediment loads for the Belyando Basin above the gauging station on the Belyando River at Mt. Douglas were estimated to permit a more accurate and explicit comparison between modelled estimates and monitoring data. These loads are as follows:
- Sub-basin modelled area: 35,143 sq. km.
- Total suspended sediment (flow weighted) supply: 1,194 kt/yr
- Total suspended sediment (flow weighted) yield: 813 kt/yr
The Upper Belyando River subcatchment is predicted to have a substantially higher rate of soil erosion (per unit area) than other Belyando Basin subcatchments (519 kg/ha/yr), although only moderate when compared to all subcatchments and other basins. The loss of soil is predicted to be largely a consequence of hillslope erosion (66%), although gully (21%) and, to a lesser extent, streambank (13%) erosion also contribute significantly. Mistake Creek, Native Companion Creek, Carmichael River and Belyando Floodplain subcatchments are identified as having intermediate rates (close to the Basin average) of soil erosion (ranging from 346 to 289 kg/ha/yr). The Sandy Creek and Fox Creek subcatchments are identified as having relatively lower rates of soil erosion (239 & 202 kg/ha/yr respectively). The average rate of soil erosion over the entire Basin (338 kg/ha/yr) is comparatively low when compared to all subcatchments and other Basins.
Total soil loss from all sources is also predicted to be greatest in the Upper Belyando subcatchment (303 kt/yr). This and total losses from other subcatchments generally reflect the rates of soil erosion, with Mistake Creek, Carmichael River, Native Companion Creek and Belyando Floodplain subcatchments having intermediate losses (208, 207, 184 & 142 kt/yr respectively), followed by Sandy and Fox Creek subcatchments with the lowest values (73 & 64 kt/yr respectively).
Water Quality Monitoring
Bainbridge et al. (2007b) report that the lack of significant flow events in the Belyando Basin during the monitoring period has resulted in less confidence in the sediment and nutrient data from the Basin. Although end of catchment mean TSS concentrations are relatively low (500 mg/L) these concentrations are likely to be higher during larger flow events. Higher mean TSS concentrations have consistently been measured over two wet seasons at the upper Belyando River (1,390 mg/L), Native Companion Creek (825 mg/L) and upper Mistake Creek (725 mg/L) which indicate that higher TSS concentrations may be generated at the end of these subcatchments in larger flow events. The apparent lower settling potential of the suspended sediment transported in these subcatchments poses an additional risk as this finer material may not be trapped effectively in the BFD, and is likely to travel further in the marine environment (Lewis et al., 2006). Nutrient concentrations are generally typical of the grazed catchments for the Belyando subcatchments, with DON generally dominating N, and P dominated by the particulate form. The relatively high concentrations of sediment leaving the Upper Belyando, Native Companion and Mistake Creek subcatchments reflect SedNet model results that predict the highest erosion rates and sediment loads in these subcatchments.
Total suspended sediment loads calculated from monitoring data at Gregory Development Road during the 2005-6 & 2006-7 wet seasons were reported to be 115 kt & 92 kt. When adjusted to the mean annual flow, these loads are 740 kt & 670 kt respectively. The 2005-6 & 2006-7 wet season flows were both well below average. While the 2005-6 & 2006-7 monitored loads were well below model predictions (813 kt), flow adjusted loads for both years were in quite good agreement.
Results of a Rapid Land Condition Assessment (adopted from Hassett et al. 2000) are presented below. The assessment has been devised to subjectively characterise condition while traversing the BDT region by vehicle. The data are based on a total of 4666 observations across the Burdekin region between 2004 and 2007.
The data were collected to provide independent information on land condition and provide a regional perspective. Resource assessment data are most useful when interpreted with other sources of data e.g. time-series remote sensing, modelling and water quality monitoring.
The estimated condition of the Belyando Basin is proportioned as follows:
- A Condition: 28%
- B Condition: 43%
- C Condition: 25%
- D Condition: 4%
Data from the Belyando Basin is based on 462 observations.
On the basis of the rapid assessment, the Belyando Basin is estimated to have the largest proportion of land in fair (B) condition (43%), followed by good (A) condition (28%) and poor (C) condition land (25%). 4% of observed land was in very poor (D) condition.
Ground Cover in the Belyando Basin is proportioned as follows:
- ( BC) Bare Cover:1%
- ( LC) Low Cover: 6%
- ( MC) Moderate Cover:36%
- ( HC) High Cover: 53%
- (VHC) Very High Cover: 3%
Data from the Belyando Basin is based on 463 observations.
On the basis of the rapid assessment (2004-2007), the Belyando Basin is estimated to have the highest proportion of land within the high (HC) ground cover category (53%), followed by moderate (MC) cover (36%) and low (LC) cover (6%) categories. 1% of land was estimated to fall into the bare cover (BC) category.
Resource Condition Summary
The Belyando Basin is very large (~ 35,000 sq. km.) and covers around 26% of the BWQIP region. Common to most of the BQWIP basins, land use is dominated by grazing on natural pastures. Less than 5% of the land area is set aside for conservation and minimal use, and production forestry. Riparian habitat throughout the basin has undergone a major decline in condition ovr the last 30 years, principally due to floodplain clearing, and is mostly assessed to be in very poor (D) condition. Belyando Basin waterways are poorly known ecologically, but numerous, persistent and highly turbid water bodies are reported to be widespread.
Hillslope erosion is identified by models as the major source of sediment and particulate nutrients affecting water quality within the Belyando Basin, while gully erosion is also identified as a significant contributor. The overall rate of soil erosion is predicted to be comparatively low, without major differences between subcatchments, possibly due to a combination of low relief and rainfall. The Upper Belyando River subcatchment is predicted to have the highest rate of soil erosion within the basin and to contribute the most sediment to the end-of-basin load, while the Sandy and Fox Creek subcatchments are predicted to have the lowest rates of soil loss. Rapid assessment of grazing land condition rates the largest portion of land area to be in fair (B) condition, while good (A) and poor (C) condition grazing land is also common. However, analyses of ground cover from satellite imagery (reference) identify extensive areas of degraded, and highly vulnerable and marginal 'D' condition land, particularly in the Upper Belyando River, Carmichael River, Native Companion Creek and Mistake Creek subcatchments.
Water quality in the Belyando Basin is predicted by models to have moderately elevated loads and concentrations of suspended sediment at the end-of-basin. Modelled and monitored sediment concentrations and loads are generally consistent; both identify the Upper Belyando River subcatchment as the major source of sediments and nutrients. Very fine suspended sediment from the Belyando Basin is thought to pose a particular risk because this finer material, with low settling potential, is more likely to reach to coast and travel further in the marine environment.
Water Quality Targets
The following water quality target was developed based on Best Management Practice Guidelines for Water Quality Improvement, extensive modelling of a range of management scenarios, preparation of a discussion paper (reference) and then, finally, a series of workshops. These preparatory activities were undertaken in collaboration with landholders (graziers and cane farmers), industry representatives, Government, the scientific community and BDTNRM staff.Attain a minimum 40% reduction in mean annual sediment load from the Belyando River Basin (measured at Mt. Douglas/Gregory Developmental Road) from current (2008) by 2058 (i.e. reduction from approximately 758 kt/yr in 2008 to 455 kt/yr by 2058).
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