Warning: The following post contains language and concepts offensive to supporters of dams or reservoirs!
To begin with the obvious, dams are controversial. They supply water, power and recreation to millions of people around the world, yet they also have irreparable effects on water ecology and the surrounding landscape. In warmer climates, they can contribute extra methane to the atmosphere from the decomposition of drowned organic matter. There is even some debate in geophysical circles over whether the world’s dams have caused the Earth’s axis to tilt and changed its rotational speed.
While the blame for these shifts in the Earth’s position cannot be entirely placed on dams (earthquakes also have the ability to affect the Earth’s rotation or position in space) it raises a valid point. We all know how much water weighs (a full bucket of water is too heavy for many people to lift easily), so hundreds of gigalitres of imprisoned water will of course have some effect on the Earth’s mass, however miniscule.
Governments love dams. So do a lot of farmers. There’s something about all that glorious expanse of water, just there for the taking, that makes them all giddy. Which is why every so often, usually near an election or after a rain/flood disaster, passionate cries of “More dams!” are heard across most commercial media channels.
Australia has suffered from a particularly malicious La Niña since early last year, with the effects probably heightened by the length and ferocity of the preceding drought. Severe flooding has been washing down most of the east coast of the country since late 2009, and even reaching the lower reaches of the dehydrated Murray River for the first time in many years.
Emotional confusion reigns as people struggle with celebrating the end of the drought and the rebirth of the Murray-Darling Basin, and coping with the devastating losses of homes, property, people and whole towns.
The recent SE Queensland floods are close to my heart, having grown up in the area. Up until last year I lived, worked and played in most of the areas that were isolated or under water last week, and I have many friends and family throughout the region who have been affected. I feel for the people who have lost—and I feel for everyone who is now being fed the belief that Wivenhoe Dam saved them from worse disaster.
Wivenhoe was built in 1984 in the upper reaches of the Brisbane River in response to the 1974 floods that infiltrated the city of Brisbane. I have seen a government report produced as part of a site suitability analysis that clearly stated the proposed site was not appropriate for the capital city’s water reservoir—it went ahead anyway.
Now government officials are claiming that Wivenhoe Dam is the reason the 2011 floods didn’t peak past the 1974 levels. More dams are being called for to prevent a repeat of the current situation under future weather events, mostly by the type of person who believes that water running out to sea is being wasted.
Dams do not prevent major floods—in some cases they can make them worse. River catchments evolve within a unique flood cycle that maintains the ecology of the river itself and the surrounding floodplains. For millennia these cycles built the landscapes and ecological communities we see today.
Building a concrete wall across a river at any point changes that cycle instantaneously, like plugging a sink while the tap’s running. The water that normally flows freely through the river’s downstream conduits builds up behind the wall, creating a floodplain where there may not have been one previously, drowning ecosystems that didn’t evolve to be underwater, and depriving downstream ecosystems of the seasonal flow of water they have evolved to receive.
Over time, landscapes change. Human stresses on the system increase from urbanisation and agriculture—water levels drop further, floodplains dry out and are built on, river banks are eroded away or stacked higher to accommodate bike paths and bridges, and the chemistry and ecology of the river delta is altered.
Soon it’s time for the catchment’s major bicentennial flood and, suddenly, the water’s got no buffer zone. The natural floodplain ecosystem that would have soaked up a lot of the water on its way down the river is gone. Hence, the roadways, narrow streets, basements and shopfronts bear the brunt.
It is heartbreaking to see the aftermath of floods like these. The mud will be washed away eventually, but the emotional and financial scars will be seen on Brisbane’s face for many years to come. Those politicians and news purveyors who find themselves in a position to spread hope and awareness to the flood-affected masses owe the truth to their listeners. Dams are more likely to increase the severity of a flood’s damaging capabilities rather than prevent it, and building more dams will not reduce the impact of future flood events.
Floods are natural occurrences and they cannot be stopped—ever. Water is omnipresent on Earth and Life is maintained through the natural cycle of this element through all organisms and systems. If you keep it out of one space, it will simply find another to run into. The best way to prevent water damage to people and property is to work WITH the water cycle, rather than try to restrain it.
© Manu Saunders 2011