Saving the Mary River

The Mary Valley Voice reported in January 2008 that 16,488 submissions on the Environmental Impact Assessment had been received at the Office of the Queensland Co-ordinator General. Of these, more than 10,000 came from people living downstream of the dam wall. While QWI states that there will be little impact on the fishing industry downstream, and on the breathtaking wildlife of the Great Sandy Strait, many of the residents are not convinced. In any case, the Mary is their river, too.

The people of the Mary River do not have politics on their side. If they voted Labor, the state government might well pause before damming the river. But they are mostly conservative folk, and of the three state electorates that contain the catchment - two (Maryborough and Nicklin) are held by Independents, and one (Gympie) by the National Party. Cate Molloy, the former member for Noosa, which adjoins the Mary River valley, was ejected from the Labor Party because of her strong anti-dam position.

Protest does not come easily to the people of the valley. Nevertheless, determined to fight for their communities, they have turned up in their hundreds to meetings to oppose the dam. Signs in the area are full of fight. But QWI has been buying up properties steadily, knowing that in doing so, it is gradually taking the heart out of the opposition to the dam. Significant sums have already been spent on these acquisitions.

Environmental issues aside, there is considerable doubt as to whether the dam represents the most cost-effective strategy to meet the needs of the projected population of Brisbane. Mary River catchment officer Steve Burgess points out that when rainfall is as low as it was in the 2000-2007 period, there will simply not be enough water to provide environmental flows to the river, deliver the predicted yield via the pipeline to Brisbane, and meet the current level of demand from downstream users.

On the other hand, in years of good rainfall, with Wivenhoe Dam and other storages operating at their normal capacity, the water will not be needed for Brisbane. In these circumstances, the dam on the Mary will be able to provide environmental flows, but these will in no way duplicate the pattern of the natural river, which floods and drains quickly.

The reality seems to be that the planners in the Queensland government are hedging their bets on the dam. If there is little rain, there will at least be some water for Brisbane, although not much for anyone else, or for the environment. If the rains return, the water can be used to support new industries in the Mary River Valley.

A consultancy report prepared for the Queensland Departments of State Development and Primary Industry and Fisheries by ACIL Tasman suggests that the new dam will reinvigorate the region’s economy, including intensive agricultural uses downstream of the dam wall. The exact nature of these enterprises is not specified, except that they will, of course, be “sustainable”. Given that, only a few kilometres away from the dam wall, one of the state’s most productive dairy farms will be inundated by the rising waters, the irony is palpable.

Eventually, an even bigger area of the valley may be flooded. The first stage of the project (to be completed by 2011) will impound roughly 153,000 megalitres of water to an average depth of 5m. If the second stage (planned for 2035) goes ahead, it will impound another 400,000 megalitres to a depth of about 8m. The dam wall is being built high enough to accommodate stage 2, although the Queensland government has sworn that the position of the sluice gates means that the water-level will reach only the stage 1 level.

This is a debate of averages. The government says the dam will flood only 4 per cent of the valley, which sounds very small. But over 36km of the river will be affected by stage 1, and 332 properties will be entirely or partly submerged. An average depth of 5m sounds reasonable, except that large parts of the dam will be much shallower than this, so that evaporation will be high, and weed infestation a constant problem.

With so many negatives, it is surely time to consider the main rationale for the dam. The case for the dam is based on continued population growth in South East Queensland. Yet only a fraction of this increase is due to natural increase of the population already living in the area. The population growth which is at the root of the Queensland government's case for this dam, is predominantly fuelled by people moving to South East Queensland from the rest of Australia, and from overseas.

From the government's point of view, population growth and economic growth form a virtuous cycle. More people create more demand, and a bigger labour force with which to meet it. But more people also need more water. Just how much more, depends upon the extent to which they can be persuaded or forced to adopt economies in the use of water.

Brisbane already has Australia's highest take-up of household water tanks (38 per cent of households have one). But beyond a certain point, unless people are to have no gardens at all, and resort to showering only two or three times a week (not perhaps such a good idea in such a steamy climate), there is a minimum below which per capita consumption cannot realistically go.