Trevallyn Dam

Water, water everywhere...

27 February 2020

Is Hydro Tasmania wasting your drinking water? The short answer is: no.


This past January, after we announced a series of planned water releases from some of our dams for the annual Paddle Week rafting and kayaking events, we had a few questions about whether this may have affected the drinking water restrictions announced by TasWater in late 2019.


And with Hydro Tasmania reporting high levels of storage in our lakes, we heard concerns that we might be hoarding water that could be used for drinking.


Rest assured, this is not the case. The easiest way to explain why is that Hydro Tasmania’s water catchments are mostly separate to TasWater’s.


While TasWater needs to draw water from nearby our cities and towns, Hydro Tasmania gets to take advantage of the more regular rainfall of the West Coast and Central Highlands, so our dams are generally very distant from where drinking water is required.


Famously, the weather on the west and east coasts of Tasmania could not be more different. The west’s rugged mountains and prevailing westerly winds combine to make it one of the wettest places in Australia. So while our hydro-electric storages can be good, a lack of rain in the eastern half of the state means towns in those areas will inevitably be drier.


There are some places however, where Hydro Tasmania and TasWater can use the same water source. In those situations, we work closely together to provide water for both parties to use in the most efficient and effective way possible.


For example, most of Hobart’s drinking water comes from TasWater’s Bryn Estyn Water Treatment Plant, on the River Derwent at Plenty. This is downstream from the Meadowbank Power Station, with Meadowbank Lake being one of several sources for the River Derwent. Water passes through the Meadowbank Power Station to generate electricity and returns to the river, where it mixes with other sources and is available for treatment.


Trevallyn Dam downstream

Some of the concern about water restrictions arose during the release of water from Launceston’s Trevallyn Dam, for kayaking and rafting in the Cataract Gorge. Lake Trevallyn is a drinking water source fed by several rivers and another Hydro Tasmania storage – yingina / Great Lake in the Central Highlands, which also feeds Poatina Power Station before the water mixes with other sources and reaches Lake Trevallyn.


These Cataract Gorge releases are very popular and are booked in advance with local clubs, but can only be done if there’s enough water available at the time. And this includes making sure that Hydro Tasmania is first meeting TasWater’s requirements.


When we’re planning a recreational release, depending on the location, we can usually use that water to generate more electricity. So no water is wasted.


It’s only at Trevallyn Dam itself that Hydro Tasmania ‘wastes’ water that could have otherwise generated electricity by running through the Trevallyn Power Station. But on the plus side, the kayaking and rafting is awesome!


Without everyone having firsthand knowledge of where all our power stations, dams, and TasWater’s water treatment plants are physically located, and how much water is available or needed at any given time, this can all appear quite complicated and is easily misunderstood.


Happily, our current water storage levels – we call it ‘total energy in storage’ (TEIS) – is very healthy for this time of year. Normally in autumn, following a dry summer, it’s typical for storage levels drop to 20-30 per cent. But currently our storages are sitting around 40 per cent, following good rainfall on the West Coast and Central Highlands during Winter and Spring 2019.


But we do need more rain in the eastern half of the state to supply our population centres.


We’re very aware of our responsibility for the health of the waterways we manage, and their importance for wildlife and the environment itself, for irrigators, for drinking water, and also for the many people who enjoy our lakes and rivers for recreation. Balancing all these needs is a daily challenge which Hydro Tasmania undertakes for the benefit of all Tasmanians.

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