"Minister Ayres can no longer squirm his way out of questions about the real cost to tax-payers of (raising the Warragamba Dam wall) project. We are talking about every Sydney household forking out a minimum of $860 for an ineffective food mitigation dam that is … nothing but a $1.6 billion in-kind subsidy to the floodplain developers of western Sydney … it will fail to alleviate flood risk and do enormous cultural and environmental damage to the Blue Mountains."  Campaign Manager at the Colong Foundation for Wilderness, Harry Burkitt, 1 March 2021

Warragamba Dam was built in 1960 to hold water from the Dyarubbin (Nepean-Hawkesbury) River as a water supply for Sydney. It also had some flood mitigation potential to hold back water when it wasn't full.

During droughts when the dam had “too little water”, a desalination plant was built at Botany Bay. Now, when it has “too much water” in floods, there is a push to raise the dam wall to increase its volume.

The idea is being championed by the current NSW LNP Perrottet government, with a fetish for poorly thought-out infrastructure projects (needlessly rebuilding a football stadium; gifting money for one NRL stadium at the expense of four others; connecting two new freeways through traffic lights; and so on). The National Party loves dams. They think it’s a dam age, when it’s really damage.

They’ve missed the current zeitgeist, led by the new federal government, turning away from ‘hard infrastructure’ projects towards ‘soft human-based services’. Nurses not hospitals. Childcare workers not centres. Aged care not aging freeways. They only need note that the likely first tasks of the National Anticorruption Commission (NACC) will be to investigate the ‘rorts’ in infrastructure projects by the former federal government.

Nevertheless, the local member, former deputy leader, Stuart Ayres, (just washing the mud off) is pedalling hard for it, saying it’s a necessary response to climate change driven weather, and to protect the low-lying parts of towns like Windsor and Richmond. The real effect however is to benefit property owners wanting to develop land that often floods in the basin.

Apart from that partisan, really dodgy, reason there are several downsides to this proposal.

Firstly, it's hideously expensive. Estimates of cost have risen from an astonishing $1.3bn in 2019 to a stonking current estimate of $1.6bn. That could pay for a lot of social housing out west.

Secondly, it will drown a vast area of ecological and indigenous importance along this river, adding to the damage the current dam did. The local indigenous and scientists are bitterly opposed.

Thirdly, and worst of all, after all that it’s highly doubtful that it can have a significant effect on flood mitigation, (it needs to be managed very differently).

Which begs the question: why don’t we use the dam for flood mitigation as it is, by lowering its water level now? In effect, use the dam in the same way that the ‘wall-raisers’ suggest, only with better management and far less cost. Which begs a further question to make this work: can we do with far less water storage for Sydney? Can we take away a substantial part of the dam’s role as water supply, lower its regular height, so that it can perform the flood mitigation role?

This would require several initiatives across the city with substantial sustainable by-products.

Firstly, it requires a different thinking about supply. Water is an already distributed resource, rain is everywhere, like sunshine on PV panels. It falls, often heavily, all over Sydney, and can be trapped locally on a house-by-house basis in water tanks to store water. The opposite, collecting it from a wide area, aggregating it into a single dam to store it, and then distributing back out to the city is a nonsense in physics and economics. More on that idea later.

Secondly, accept that floods will still occur, although ameliorated. Stop construction of homes in flood-prone areas - this alternative proposal can't be used to increase developer profits. The money saved by not building the dam wall can be redirected into better town planning, developing sensible densities for the towns, and buying up vulnerable land.

Thirdly, areas that will continue to flood need to be better landscaped and revegetated with trees to minimise the erosion of riverbanks, even if it means reducing areas for farm production. It is ludicrous for farmers to be demanding compensation for loss of land swept away, when it is their land clearing of trees along the banks that has caused the erosion.

And fourthly, put an end to a minor irony: the river flats are currently used for growing commercial areas of grass, ‘turf manufacturers’, a product that ultimately increases the demand for water in the suburbs. Grass in individual backyards is a lost opportunity for better vegetation: trees to reduce the heat island effect and support birdlife, vegetables and fruits grown locally, or plants and shrubs for wildlife. Grass is an ecological desert, it’s time to end to the turf wars.

Which brings us back to the first issue of how to use rainwater to substitute for the loss of dam water? Two linked issues: price water to encourage everyone to minimise dam water; and encourage them to use tank water where possible.

More than half (55%) of water in a house is used for non-potable uses – toilets, clothes washing and external (gardens / car washing). These can all be done by rainwater from a tank. How to incentivise residents to swap? Well, water’s too cheap. We need a pricing policy that increases costs with the amount used.

A house could have 50% of current average usage at low cost. More than that would come at a much higher rate, encouraging alternative sources of water such as tanks. A pricing policy is a far better way to encouraging sensible use than the latest approach in LA, fitting flow restrictors to celebrity mansions, such as Madonna or Sylvester Stallone.

Most Sydney houses are freestanding homes, but there would need to be ‘carve outs’ for how we define a single ‘dwelling’ for costs, and exemptions for apartments – which are already substantially more sustainable by their location and efficiency. Profligate users would pay their way, the excess money set aside for times when the de-salination plant (using high energy reverse osmosis) is needed. It is, after all, ‘bottled electricity’ in Premier Bob Carr’s memorable phrase.

Now tanks. We know that eighteen years of Basix has led to rainwater storage tanks being installed in almost every new individual dwelling, with a consequent reduction in water consumption. We also know that many tanks are permanently full, lying idle, not being used, the water becoming a liability, not an asset.

We need to ensure all houses that can have, or want, a tank can have one; and we need an education campaign to ensure optimal use. This where we direct a small portion of the ‘dam-raising monies’ so every suburban house has an appropriate sized tank, say two to ten thousand litres, and which is used safely for all the purposes that do not need to be potable: toilets, washing machines or cars, gardens, hosing the lawn, or the concrete.

The NSW Government could then turn the remaining monies saved by ‘lowering Warragamba Dam’ and not raising the wall, into relocating the worst flood-affected residents and by urgently building evacuation roads in western Sydney for the remaining residents. Damn dam. Win win.

Tone Wheeler is an architect / the views expressed are his / contact at [email protected]