Iconic lake Pedder
The original Lake Pedder was 10 square kilometres in area. By contrast, the Huon-Serpentine impoundment (which now covers Lake Pedder) occupies 242 square kilometres in area.
Its famous quartzite beach was 1km wide and 3km long.
The protection provided by the Lake Pedder National Park status, granted in 1955, was revoked by the Tasmanian government in 1967.
Lake Pedder was submerged by the Hydro Electric Commission in 1972 in order to provide part of the water inflow to the Gordon River power scheme being constructed at that time.
The Huon-Serpentine impoundment is a vast diversion pond. It captures the waters of the Serpentine and upper Huon Rivers and elevates those waters so that this water feeds by gravity into the Lake Gordon impoundment.
The volume of water that is sitting 15 metres above the original Lake Pedder is static and never used. It is only the top one metre that flows through the McParland Pass canal into Gordon. The other 14 metres of water only purpose is to elevate the impoundment level to flow into the pass.
Energy generation implications
The Gordon Power Station has a maximum generating capacity of 432 Megawatts – i.e. when all of its three turbines are spinning.
The Gordon scheme’s actual sustained output (this is based on average water inflows in any year) is approximately 140 Megawatts average, which equals about 10% of the state’s hydro-electric output.
Of this, the Huon-Serpentine impoundment supplies 40 percent of water inflow.
Lake Pedder’s flooding thus provides 4% of the state’s hydro-electric output. This translates to 3.2% of the state’s total electricity demand (from all power sources).
In the context of alternative supply, withdrawing total energy from Pedder waters would be equivalent to the electricity output of a large wind farm such as is currently being built at Cattle Hill (50 – 60 turbines).
Twenty large industries consume 60% of Tasmania’s power demand.
Five bulk power industries consume 50% of Tasmania’s electricity demand.
Nyrstar zinc smelter uses 11%. The Bell Bay aluminium smelter uses 31%. Temco uses more than 5%. Temco’s future is uncertain.
The Gordon Scheme was implemented in order to provide electricity to cater for a planned expansion of the Comalco furnace potline at the time.
Restoration of Lake Pedder would be the largest ecological restoration project in Australia and the world. There is a growing number of significant dam removals and restorations in other parts of the world.
An area of 15,000 hectares (equivalent in area to 6,000 MCG ovals) would need to be restored to its pre-flooded state in order for this to happen.
Scientific research (based on depth sounding and diving) has found that the original Lake Pedder beach and associated dune system remain intact, largely undisturbed by the flooding.
In 1995 a federal House of Representatives Committee of Inquiry found restoration to be technically feasible.
Header Photo Credit : Dennis Garrett