Upper Burdekin River Basin
Upper Burdekin subcatchments
The Upper Burdekin Basin is comprised of 17 subcatchments, as follows:
- Allingham Creek Sub-catchment
- Basalt River Sub-catchment
- Burdekin River (above Dam) Sub-catchment
- Burdekin River (Blue Range) Sub-catchment
- Camel Creek Sub-catchment
- Clarke River Sub-catchment
- Douglas Creek Sub-catchment
- Dry River Sub-catchment
- Fanning River Sub-catchment
- Gray Creek Sub-catchment
- Hann Creek Sub-catchment
- Keelbottom Creek Sub-catchment
- Kirk River Sub-catchment Sub-catchment
- Lolworth Creek Sub-catchment
- Running River Sub-catchment
- Star River Sub-catchment
- Upper Burdekin River Sub-catchment
SedNet Modelling of Water Quality
Model results for the Upper Burdekin Basin are summarized as follows:
- Basin modelled area: 40,116 sq. km.
- Source contributions: Hillslope = 59%; Gully = 18%; Streambank = 23%
- Total suspended sediment (flow weighted) supply: 2,308.1 kt/yr
- Total suspended sediment supply (flow weighted; normalized to area): 575 kg/ha/yr
- Suspended sediment end-of-basin (flow weighted) yield: 2,085.1 kt/yr
- Event Mean Concentration (flow weighted): 566.5 mg/L
- Mean Annual Flow: 3,680,639 ML
Overall, hillslope erosion is identified as the major source of sediment and particulate nutrients affecting water quality in the Upper Burdekin basin (59%), although streambank (23%) and gully (18%) erosion are also predicted to be significant contributors. Loss of sediment and associated particulate nutrients from all sources (supply) is evidently significant (2,308 kt/yr) because of the very large (modelled) area of the Upper Burdekin basin (40,116 sq km). This loss equates to 575 kg/ha/yr, which is moderate when compared to all sub-catchments and other basins.
Modelled suspended sediment loads for the Upper Burdekin basin above the gauging station on the Burdekin River at Sellheim 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: 35,894 sq. km.
- Total suspended sediment (flow weighted) supply: 1,941 kt/yr
- Total suspended sediment (flow weighted) yield: 1,756 kt/yr (exported from sub-basin i.e. 185 kt deposited on floodplain)
The two Burdekin River flood plain sub-catchments (Blue Range & above Dam) are predicted to have substantially higher rates of soil erosion (per unit area) than other Upper Burdekin Basin sub-catchments (1,095 & 1,082 kg/ha/yr respectively). These losses are largely a consequence of high predicted rates of streambank erosion. Sediment loss from Running River sub-catchment, while predicted to be high (834 kg/ha/yr), is probably overestimated on the basis of monitoring data. Kirk, Running, Fanning, Star, Keelbottom, Douglas, Clarke, Camel, Gray and Dry River sub-catchments are identified as having moderate levels of soil loss (ranging from 791 to 454 kg/ha/yr). The Upper Burdekin, Hann, Lolworth, Basalt & Allingham Creek sub-catchments are identified as having relatively lower levels of soil loss (ranging from 378 to 236 kg/ha/yr).
Total loss of sediment from all sources is predicted to be greatest in the two Burdekin River floodplain (above Dam & Blue River) and Clarke River sub-catchments (441, 300 & 334 kt/yr respectively). Losses from the two Burdekin River sub-catchments are largely a consequence of high predicted rates of streambank erosion. The Upper Burdekin, Star & Lolworth Creek sub-catchments are predicted to deliver substantially reduced sediment loads to the river system (167, 123 & 103 kt/yr respectively). The remaining subcatchments deliver progressively less sediment to the Upper Burdekin Basin streams and water bodies (ranging from 94 to 28 kt/yr). The Allingham Creek sub-catchment is predicted to lose the least sediment (28 kt/yr).
Water Quality Monitoring
Bainbridge et al. (2007) report that the upper Burdekin River sub-basin has been identified as the dominant contributing arm of sediment and nutrient loads to the Burdekin Falls Dam (BFD). Within this sizable sub-basin (36,140 km2), the north and north-western tributaries (Clarke River, upper Burdekin minor sub-catchment above Greenvale, Camel Creek, Dry River, Gray Creek and Maryvale Creek) generate elevated sediment concentrations, with mean TSS concentrations ranging between 1,505-4,075 mg/L for these sites. This region consists of relatively steep landscapes and hosts old sedimentary rock deposits which are prone to erosion. Nutrients also measured at the Clarke River catchment show elevated particulate nutrients associated with the high sediment concentrations, and particulate nutrient concentrations are likely to be similarly high at the other tributaries within this region. The basaltic catchments (Basalt River, Fletcher Creek, Lolworth Creek) in the central west of the upper Burdekin sub catchment have lower mean concentrations which range between 250-820 mg/L. These catchments have elevated concentrations of the dissolved organic and inorganic phases of phosphorus (DOP and FRP), most likely sourced from the high levels of phosphorus naturally found in the basaltic landscape. However, the apsorption potential of basaltic soils has not been quantified in the Burdekin catchment. In the eastern region the Star and Running Rivers contribute sizable proportions of flow to the end of the upper Burdekin sub-basin due to their rainforest headwaters in the Mount Spec Range. However, sediment concentrations (and loads)measured at both the Running and Star Rivers are low, with mean TSS concentrations of 155 and 165 mg/L, respectively. Nutrient concentrations measured at Running River are also lower than typical concentrations in the Burdekin Region, with nitrogen dominated by DON, the ‘natural’ form of nitrogen leakage from little modified landscapes.
Total suspended sediment loads calculated from monitoring data at Sellheim during the 2004-5, 2005-6 & 2006-7 wet seasons were reported to be 1,700 kt, 1,760 kt & 2,800 kt. When adjusted to the mean annual flow, these loads become 2,730 kt, 2,500 kt & 2,300 kt respectively. The 2004-5 & 2005-6 wet seasons had below average flows while the 2006-7 wet season was above average. While the 2004-5 & 2005-6 monitoring data compare closely with modelled predictions, monitoring data from the 2006-7 wet season and flow adjusted loads for the three years suggest that the modelled predictions may be underestimating the total suspended sediment load leaving the Upper Burdekin Basin.
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 Upper Burdekin Basin is proportioned as follows:
- A Condition: 27%
- B Condition: 37%
- C Condition: 30%
- D Condition: 6%
Data from the Upper Burdekin Basin is based on 1799 observations.
On the basis of the rapid assessment, the Upper Burdekin Basin is estimated to have the largest proportion of land in fair (B) condition (37%), followed by poor (C) condition (30%) and good (A) condition land (27%). 6% of land is in very poor (D) condition.
Ground Cover in the Upper Burdekin Basin is proportioned as follows:
- ( BC) Bare Cover: 1%
- ( LC) Low Cover: 19%
- ( MC) Moderate Cover:33%
- ( HC) High Cover: 32%
- (VHC) Very High Cover: 14%
Data from the Upper Burdekin Basin is based on 1812 observations.
On the basis of the rapid assessment (2004-2007), the Upper Burdekin Basin is estimated to have the highest proportion of land within the moderate (MC) ground cover category (33%), followed by high (HC) cover (32%) and low (LC) cover (19%) categories. 14% of land was estimated to fall into the very high cover (VHC) category.
Resource Condition Summary
The Upper Burdekin Basin is the largest in the Burdekin Dry Tropics (~ 40,412 sq. km.) and covers around 30% of the BWQIP region. Common to most of the BQWIP basins, land use is dominated by grazing on native pastures. Approximately 11% of the land area is set aside for conservation and minimal use, mostly as remnant native vegetation, while a great many abandoned and operational mines are located throughout much of the basin. The condition of riparian habitat within the basin varies greatly between sub catchments, from good (A) to very poor (D). Similarly, there is great diversity in the value of aquatic habitats, and knowledge of their condition and ecology between sub catchments. Waterways vary between largely sandy, dry ephemeral creek systems to permanently flowing clear-water rivers and creeks that originate in mountain rainforest.
Hillslope erosion is identified by models as the major source of sediment and particulate nutrients affecting water quality within the Upper Burdekin Basin, while stream bank and gully erosion are also identified as a significant contributors overall. The rate of soil erosion for the Basin overall is predicted to be moderate and close to the BWQIP region average, with individual sub catchments predicted to lose up to twice the Burekin Water Quality Improvement Plan region average. The Burdekin River (above dam) and Burdekin River (Blue Range) sub catchments, in particular, are predicted to have high rates of soil erosion and to contribute substantially to the total sediment load at end-of-basin. The Clarke River sub catchment is also predicted to contribute substantially to the end-of-catchment sediment load. Rapid field assessment of grazing land condition rates the land area to have quite similar proportions in good (A), fair (B) and poor (C) condition overall. Analyses of ground cover from satellite imagery (references) identify some quite extensive areas of chronic 'D' condition land, and highly vulnerable and marginal 'D' condition land, while stream bank and gully erosion are reported to be extensive in some areas.
Water quality in the Upper Burdekin Basin is predicted by models to have moderately elevated loads and concentrations of suspended sediment at the end-of-basin during wet season flow events. However, water quality monitoring from the Burdekin River at Sellheim over 5 years have recorded still much higher sediment concentrations and loads than predicted by models. While the Burdekin Basin is evidently the major contributor of sediment and particulate nutrient loads to the BFD, it is estimated that as much as 60% may be trapped within the dam during an average event flow, thus reducing quite significantly the total suspended sediment contribution from the basin to sediment and nutrient loads at the Burdekin River mouth. However, model predictions are also thought to be significantly underestimating the total suspended sediment load leaving this basin.
Water Quality Targets
The following water quality Resource Condition 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 NQ Dry Tropics staff.
Attain a minimum 40% reduction in mean annual sediment load from the Upper Burdekin Basin (measured at Sellheim) from current (2008) by 2058 (i.e. reduction from approximately 2,150 kt/yr in 2008 to 1,290 kt/yr by 2058).
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