Clarke River

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Subcatchments

Smaller Catchments within the Clarke River Catchment include:

Topography

Vegetation

Riparian Habitat

The following information is summarized from the ACTFR report: Assessing the condition of riparian vegetation in the Burdekin catchment using satellitte imagery and field surveys by Leo Lymburner and John Dowe. 2006. This report can be accessed from the report section below.

iTRARC analysis of Riparian Habitat indicates that this subcatchment hasn’t undergone much change in the last 30 years. In the 1970s riparian habitat was already in relatively poor condition in comparison with Maximum iTRARC scores, and the field survey data indicate that the riparian zones are still in poor condition. The combination of very low amounts of regeneration (zero in three out of 4 sites) and low weediness may be indicative of high grazing pressure.

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Wetlands

The following information is summarized from the ACTFR report: Assessing the condition of Wetlands in the Burdekin catchment using existing GIS and field knowledge for CCI by Mirjam Maughan, Damien Burrows, Barry Butler, Leo Lymburner and George Lukacs. 2006. This report can be accessed from the report section below.

This is a very large but mostly dry sub-division. The Clarke River itself is a largely dry sandy, seasonal river channel. However, the headwaters of this system and those of several of the key tributaries (eg, Broken, Junction, Maryvale) begin in basalt country, and thus contain significant permanent, clear-water waterbodies fed by basalt springs, or in the case of the Broken River, limestone. Although the waterbodies of this area have mostly not been studied (except for Burrows and Butler 2003 who undertook limited sampling of water quality and macroinvertebrates at sites in the upper Clarke River, Junction Creek and Maryvale Creek), their permanency and spring water source give them high ecological values. Condition of the spring-fed waterholes is generally good, though some of the tributaries are poorly known ecologically.

Clarke River wetland condition summary...

Water

Both hillslope and gully erosion are identified as major sources of sediment and particulate nutrients affecting water quality within the Clarke River subcatchment (65% & 29% respectively). 15% of hillslopes or 998 sq. km. are estimated to have ground cover less than 50%. Loss of sediment and particulate nutrients from all sources (supply) is considered to be elevated and at moderate levels (516 kg/ha/yr). Moderate to high concentrations of sediments are predicted (679 mg/L) at the end-of-subcatchment.

For more information see the Water Quality Information Page

Landuse

Principle land uses within the Clarke River subcatchment as a proportion of total area:

Grazing: 90%

Conservation & minimal use: 9.6%

Water: .25%

Urban & semi urban: Limited urban & semi urban activity use identified.

Mining: Limited mining activity use identified.

Grazing Land

Clarke River is a relatively large sub-catchment where the land use is dominated by grazing on natural pastures. Approximately 10% of the land area is set aside for conservation and minimal use (QLUMP).

Land Condition

Definition of ABCD land condition framework

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 Clarke River sub-catchment is proportioned as follows:

A Condition: 20%
B Condition: 47%
C Condition: 27%
D Condition: 6%

Data from the Clarke River sub-catchment is based on 355 observations.

On the basis of the rapid assessment, the Clarke River sub-catchment is estimated to have the largest proportion of land in fair (B) condition (47%), followed by poor (C) condition (27%) and good (A) condition land (20%). 6% of observed land was in very poor (D) condition.

Ground Cover

Ground Cover in the Clarke River sub-catchment is proportioned as follows:

( BC) Bare Cover: 1%
( LC) Low Cover: 16%
( MC) Moderate Cover: 42%
( HC) High Cover: 36%
(VHC) Very High Cover: 5%

Data from the Clarke River sub-catchment are based on 335 observations.

On the basis of the rapid assessment (2004-2007), the Clarke River sub-catchment is estimated to have the highest proportion of land within the moderate (MC) ground cover category (42%), followed by high (HC) cover (36%) and low (LC) cover (16%) categories. 1% of land was estimated to fall into the bare cover (BC) category.

Resource Condition Summary

Clarke River is a relatively large subcatchment where the land use is dominated by grazing on native pastures. Approximately 10% of the land area is set aside for minimal use, while there are many abandoned and operational mines throughout the subcatchment. The condition of riparian habitat in the subcatchment has undergone relatively little change in the last 30 years and is currently assessed to be poor (C). Field surveys indicate little riparian regeneration and few weeds, suggesting significant grazing pressure. The Clarke River itself is a largely dry, sandy and seasonal river channel. However, the headwaters of this system and those of several of the key tributaries (eg, Broken, Junction, Maryvale) begin in basalt country, and thus contain significant permanent, clear-water waterbodies that are fed by basalt springs, or in the case of the Broken River, limestone. Their permanency and spring-fed water source give them significant ecological values. The condition of the spring-fed waterholes is thought to be generally good, though little is known about the ecology and condition of aquatic habitats of some of the tributaries.

Both hillslope and gully erosion are identified by models as major sources of sediment and particulate nutrients affecting water quality within the Clarke River subcatchment. The rate of soil erosion is predicted to be moderate and close to both the basin and BWQIP region averages, while the total soil loss to waterways from the subcatchment is comparatively high due to its large area. Grazing land condition is assessed as having the highest proportion in fair (B) condition, followed by poor (C) and good (A) condition land. Some very poor (D) condition was also observed. This is also reflected in the rapid ground cover field assessment (2004-07), while analysis of satellite imagery (reference) identifies some areas of vulnerable and marginal 'D' condition land.

Water quality in the Clarke River subcatchment is predicted by models to have moderately elevated sediment concentrations during wet season event flows. Comparisons are difficult to draw between the monitoring and modelling datasets due to the small sample size collected over only a single wet season but, while generally consistent, the monitoring data recorded higher concentrations of sediment than predicted by the models.

Clarke River is identified as a priority subcatchment for rehabilitation on the basis of its contribution to the total sediment load within the basin, and substantial areas of vulnerable and marginal 'D' condition land.

Draft Environmental Values

The aquatic ecosystem values of the Clarke River subcatchment are poorly known and, while considered to be Slightly to Moderately Disturbed (SMD) as a consequence of the surrounding land use for cattle grazing, the biological communities are thought to remain in a healthy condition and ecosystem integrity is likely to be largely retained. No High Ecological Value (HEV) waters are identified in the subcatchment. The human use Environmental Values of the Clarke River subcatchment are understood to include recreation (swimming, camping & visual appreciation), drinking water, stock watering, and the cultural and spiritual values of the Kudjala and Badhun traditional owners.