Gordon-Franklin Catchment

Contents

1. About the catchment

2. River Health

1. About the catchment

The Gordon-Franklin catchment is the largest of the nominated 48 land & water management catchments in (5,900 km2), and lies almost completely within the Tasmanian Wilderness World Heritage Area. The only significant human-related activity that has had a significant impact on the catchment has been the construction of a hydro-electric power scheme that resulted in the creation of the two largest lakes in Tasmania, (242 km2) and (272 km2). Water from both these lakes is used to generate power through the Gordon , which discharges into and consequently regulates flow in the lower . Some of the highest rainfall in Tasmania occurs in this catchment, which ranges broadly between about 1600 mm in the driest parts of the catchment to over 2500 mm in the wettest areas. Drainage from the entire catchment is discharged into , where there is a substantial aquaculture industry based on salmonid production and a tourist industry largely focussed on access to the lower Gordon River and the World Heritage Area.

- 1 - 2. River Health at The Australian River Assessment This site is located in the upper reaches of the System (AUSRIVAS) is a Franklin River and is within the Franklin - Lower standardised national system for Gordon Wild Rivers National Park. The river is in assessment of river condition that near pristine condition and is surrounded by cool uses benthic macroinvertebrates. temperate rainforest. The only disturbance is in the The AUSRIVAS models predict the form of a small picnic and tourist information area aquatic macroinvertebrate fauna and a riverside walking track (Franklin River Nature that would be expected to occur Trail). at a site in the absence of The river at this site is approximately 20 metres environmental stress such as wide and is characterised by riffle and run pollution, habitat degradation or sequences over boulder / cobble substrate. Water flow regulation. A comparison of quality is excellent with low conductivity and the macroinvertebrates expected turbidity. to occur at the test site with those actually collected (O/E ratio) AUSRIVAS assessments returned O/E scores in provides a site specific measure of Band A for both habitats, indicating a rich the biological impairment of the macroinvertebrate fauna. The riffle habitat in test site. Further details about particular had a high diversity of Ephemeroptera AUSRIVAS can be found at: (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies) which accounted for 50% of the taxa www.ausrivas.canberra.edu.a and 55% of all individuals collected. u/ausrivas. A single site is monitored for river health in this catchment. Season O/E Taxa Band O/E Taxa Band Riffle Edgewater

Spr03/ Au04 1.07 A 0.97 A

1.4

1.2

1

0.8

0.6 O/E Taxa 0.4 Riffle 0.2 Edgewater

0 Spr03/ Au04 Season Fig: Franklin River at Lyell Highway. Fig: Combined season AUSRIVAS O/E Taxa scores for the Franklin River at Lyell Highway.

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