Broken River subcatchment draft HEV waters
The Broken River rises in the rainforest covered north-eastern highlands of the Clarke Range at Eungella, west of Mackay. The headwaters of the Broken River and its eastern tributaries receive average rainfall ranging between 1300 and 2000 mm, mainly during the wet season months of December through to April. This provides perennial river systems that flow down the steep and remote valleys of rugged granite hills. The main Broken River valley runs north-west, widening near the confluence of Massey and Urannah Creeks before joining the Bowen River valley near Emu Plains. Most of this subcatchment is steep and inaccessible with limited development. Large areas of the upper catchment are in the protected estate including national park and state forests. The steepness has limited agricultural use and clearing, and has resulted in much of the subcatchment area remaining largely intact and in a natural state. Cattle grazing takes place on the lower slopes of the valleys and dairying occurs in the headwaters, with some irrigated improved pastures limited to riparian lands adjacent to the upper reaches.
The Eungella National Park and Crediton State Forest contains lush rainforest remnants and grassy open eucalypt forest set within the spectacular Clarke Range which reaches a height of 1280 at the summit of Mt Dalrymple. This isolated mountain refuge lies close to the boundary between subtropical and tropical rainforests and supports species from both vegetation types. Eungella National Park is one of Queensland’s most ecologically diverse parks with 860 plant species, including plants close to their distribution limit such as the Regent bowerbird (Sericulus chrysocephalus). The number of endemic species suggests that the Clarke Range provided important refugia during times of rainforest contraction. Unique animals found in this park includes the endemic Eungella spiny crayfish (Euastacus eungella), Eungella honeyeater (Lichenostomus hindwoodi), four endemic species of leaf tail gecko (Phyllurus sp.), two skinks (Eulamprus spp.) as well as three frogs, Eungella tinkerfrog (Taudactylus liemi), Eungella dayfrog (Taudactylus eungellensis) and the now thought extinct, Gastric Brooding frog (Rheobatrachus vitellinus). The area is also renowned for platypus (Ornithorhynchus anatinus) viewing.
Large areas of the Broken River subcatchment have been assessed by the WQIP ecological values technical panel to be “effectively unmodified” (ANZECC 2000) and have been identified as containing High Ecological Value (HEV) waters. These include the waters within the Eungella National Park and the Gamma, Crediton and Macartney State Forests. The majority of this subcatchment downstream of these areas to Emu Creek has intact remnant vegetation and has also been categorised as containing HEV waters. These waters closely match the area listed on the Directory of Important Wetlands as the Broken River, Urannah Creek and Massey Creek Aggregation. However, waters within cleared areas of the Eungella hinterland used for dairy and other activities, and sections of the Broken River channel, contaminated from intensive animal production in the upper headwaters and impounded for the Eungella Dam and sections downstream of the dam have been excluded and not identified as HEV waters because of significant changes to water quality and flow.
Tributaries of the very upper reaches of the Broken River flow south-west through cleared land used for dairy and irrigated hay and silage, before entering Eungella National Park and Criticon State Forest. As a consequence of this land use the upper Broken River has had water quality problems for many years. Frequent algal blooms and high faecal coliforms continue to impact on the waterway health. The E. coli contamination in Broken River has been at levels considered unsafe for swimming by the EPA. The very upper reach of Bee Creek is similarly affected and been excluded as a HEV water body. All five diary farms in the Eungella region are participating in a programme to improve environmental impacts of their activities by increased fencing, weed control and effluent containment.
The presence of the Eungella Dam (listed on the Directory of Important Wetlands) reduces dispersion and dilution of upstream pollution sources and reduces aeration and mixing. Ecological values of reaches immediately downstream of the dam are significantly affected by the river being impounded and by patterns of water release. These effects are somewhat ameliorated by the inflows contributed by tributaries, Massey, Urannah and Grant Creeks reducing the water quality impacts of the dam and the associated flow regime changes. However, transfer of water through Broken River to Collinsville Weir, which supplies industrial and domestic use at Collinsville and for coal mining operations, may carry water quality effects from altered impoundment waters through to the Bowen River. The Eungella Dam is listed on the Directory of Important Wetlands noted for its water bird habitat but is not identified as being HEV waters because it is a modified water body. The dam has also been stocked for recreational fishing for Sooty Grunter (Hephaestus fuliginosus), Sleepy Cod (Oxyeleotris lineolatus), Barramundi (Lates calcarifer) and very low numbers of Southern Saratoga (Scleropages leichardti). There are also unconfirmed rumours of illegal translocation of Red Claw Crayfish (Cherax quadricarinatus) into Eungella Dam. If true this could affect endemic populations of crayfish.
In the lower sections of the reach between the dam and Urannah Creek there also appears to be signs (observable on Spot 5 imagery) of erosion on ancient high alluvial deposits. The extent of this erosion and how it has affected water quality conditions is not known. This area is important habitat for the recently discovered Irwin’s turtle (Elseya irwini) that is known only from the Bowen-Broken system and has been nominated for the list of threatened species. The area is also renowned for platypus (Ornithorhynchus anatinus) viewing.
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