|
The length of undisturbed rivers (wild rivers) and their reservation status. Extensive development of water resources for agricultural, industrial and domestic uses, coupled with questionable land management practices has had major impacts on Australian river systems since European settlement. As a result, undisturbed or wild rivers are now rare. Such rivers are valuable for baseline or reference areas for the protection of bio- and geo-diversity, maintenance of downstream water quality and flow, and recreational and aesthetic experiences (Stein et al. 2001). A full and detailed inventory of the number of rivers that are still essentially undisturbed, provides a manner in which to identify a river - perhaps the last example of a particular type - that might be under threat from proposed development or activity within its catchment.
The level of disturbance to a river was measured by deriving indicators based on four major sources of catchment disturbance with the potential to significantly alter river processes including: land-use activity, settlements and structures, infrastructure, and extractive industries and other point source pollution. These indicators were combined with another set of indicators based on alterations to flow regime from in-stream disturbances: impoundments, flow diversions or discharges, and levee banks. The results were modified according to the level of disturbance to all upstream sections and their tributaries. These then formed a composite River Disturbance Index (RDI), which provided an overall RDI rating for each river. Undisturbed rivers were then defined within the context of such ratings for all Australian rivers along a continuum from near pristine (0.0) to highly degraded (1.0) (Stein et. al. 1998 and 2001). In Tasmania, a threshold of ≤0.01 was chosen for the RDI and for a Sub-Catchment Disturbance Index (SCDI), in combination with a minimum catchment area of 1,000 ha criterion to identify wild rivers (see map below).
Tasmanian wild rivers make up 25% of the total rivers distinguished on the 1:250,000 scale Auslig topographic maps and TOPO-250K digital database. Ninety-six percent of the identified Tasmanian wild rivers are within the Comprehensive, Adequate and Representative (CAR) reserve system as defined during the Regional Forest Agreement (RFA). The Tasmanian and Commonwealth governments agreed (through the RFA) that the CAR system "provides adequate protection for wild rivers". The objectives, primarily the protection of conservation values, for reserve management are set out in the Nature Conservation Act 2002, the National Parks and Reserves Management Act 2002, and the associated National Parks and Reserves Regulations 1999 and Wildlife Regulations 1999. Although, wild rivers are not specifically covered in the above Acts, their values are protected as any of the other conservation values in reserves. Statutory management plans can target wild rivers in reserves as necessary, although such targeting is currently minimal, if at all (DPIWE 2002). The remaining four percent of the wild rivers outside the reserves are on private, council and Hydro Electric Corporation land. Although these wild rivers are outside the management of either DPIWE or Forestry Tasmania, the DPIWE - administered Threatened Species Protection Act 1995 and Aboriginal Relics Act 1975 apply to all land tenures and therefore affords these wild rivers some protection (DPIWE 2002).
State of Environment Tasmania Indicator, Penny Wells |
