Monday 17/9/2007 Page: 6
THIS year Tasmania has seen record demand for electricity and record lows in its hydro power generating water storages. It is a situation that must be cause for concern for the State Government, Hydro Tasmania and consumers. Climate change has seen Hydro Tasmania's water storages drop by more than half over the past decade and there's not a lot of optimism that the situation will improve.From a high of 79 per cent of capacity in 1997, Tasmania's 50 hydro storage lakes and dams dropped to a 40-year low of just 17 per cent in May this year. Despite record rainfall in some catchment areas last month, they are still only 27 per cent of their 17,100-gigalitre capacity. On Monday, June 18, Tasmanians used a record amount of electricity. The new generation peak during a chilling winter night saw 2420MW of electricity used. Hydro's total generating capacity is 2568MW.
In the past 12 months the company has spent more than $100 million on importing power from the mainland via Basslink and running the gas-powered Bell Bay power station, now owned by Alinta. The cost of electricity for domestic and commercial consumers is set to rise by around 15 per cent with Tasmanian energy regulator Andrew Reeves announcing his final determination next month.
Rainfall holds the key to Hydro Tasmania's fortunes and spokeswoman Helen Brain says predictions are for little change up to 2040. "Hydro Tasmania has been working with the CSIRO in modelling likely trends in Tasmania's climate due to global warming. The long-term prediction for rainfall is that it is likely to be less than in the past," she says. Hydro Tasmania's longterm intention is to operate Great Lake between 30 and 60 per cent of capacity. "The highest we have seen it (Great Lake) was in 1997 when it was 78 per cent full." In May this year it was at 12 per cent of capacity and it currently stands at around 20 per cent.
Work to improve inflow to storages, cloud seeding and alternative sources of electricity are all on the agenda for Hydro Tasmania. A $2 million upgrade of the Liawenee canal, which carries water from Lake Augusta to Great Lake, was completed earlier this year. It allows for higher flood flows and more water entering the struggling Great Lake.
"The value of stored water varies enormously depending on the season and on the catchment and how widespread the rainfall is," Ms Brain said. "As an indication, 10mm extra (rainfall) over the entire West Coast or Great Lake catchments is worth about $3 million. Over Lake Gordon it would be worth about half that amount. "The rainfall is worth more in winter over the big catchments as everything is already wet and that water runs off into the storages.
"It's worth almost nothing in summer if the catchment is dry, as it would be soaked into the soil with no runoff resulting in the catchment." The Hydro's annual cloud seeding programme has been expanded this year to help non-hydro storage regions as well. Already more than 20 flights have been made. "Cloud seeding is used to enhance inflows to a number of Hydro Tasmania's catchments," Ms Brain said. "The choice of catchment depends on the presence of favourable seeding conditions and generation demand. "Results from joint HEC-CSIRO trials conducted in the 1980s indicate that there is about a 4-5 per cent increase in annual rainfall. "Incremental run-off from seeded events varies considerably, depending on antecedent catchment conditions," she says.
But cloud seeding is not all silver lining, with the West Coast Council regularly complaining of its effect on tourism and other activities. A study is being conducted to ascertain any adverse effects. The use of the $1.2 billion Basslink cable to import power, the gas-fired Bell Bay power station and wind energy are all regularly contributing to the Tasmanian electricity grid.
In its first year of operation, Basslink was used to buy 1470MW of power from the mainland at a cost of $56 million although it was used to export less electricity to a similar value. In that period Hydro Tasmania also spent an extra $20 million on gas for Bell Bay to reduce the pressure on hydro storages. Wind power from associated company Roaring 40s contributed a handy 48MW during the cold snap in June.
August was a bright spot for hydro generation with rain boosting storages by 7.5 per cent to 27.1 per cent, but this was 4.5 per cent lower than at the same time last year. The rise was mostly a result of the heavy rains between August 8 and 11 that caused widespread flooding. The Pieman, Forth and Derwent rivers all experienced peak flows during the period that exceeded previously recorded maximum flows. It is a phenomenon that we may see repeated in the future.
An HEC-CSIRO-UTAS climate change report says that over the next 30 years expectations are that the North-East area of the State will trend towards lower rainfall (by 8 per cent) with higher maximum and minimum temperatures and higher evaporation. The remainder of the State will trend to higher rainfall (7 to 11 per cent) with higher minimum temperatures and, on the West Coast and highlands, a decrease in evaporation. The bottom line is that Tasmanians will have to get used to buying electricity from the mainland and gasfired power station operators like Alinta.
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