Letters to the Editor, The Herald-Sun, 31 December 2007.

Letter of the day.

Politicians assuring us that existing plans to clean up the Yarra just need to be enacted fail to join some big obvious dots.

The Yarra is at its dirtiest after it rains because of the huge volumes of stormwater that runs off our roofs and roads. 

Before Melbourne was here, almost all of that water would have been taken up by trees.

If we are going to have any hope of controlling pollution in the Yarra, we will need to capture and use as much of the excess stormwater as we can.

As it happens, the volume of stormwater emptying from Melbourne’s drains is about the same as the volume of water that we use from our reservoirs.

So why do we need a desalination plant when our city produces an abundance of water that is making our rivers sick, and that we could harvest with a fraction of the energy need for desalinated water?

Dr Christopher Walsh, Parkville


Opinion, The Age, 2 November 2007.

Give tanks a chance.

Paul Baxter's claim that a 50-kilolitre tank is required to substantially cut household water usage must assume a small roof area and a need for 100 per cent reliability. Yield is much more important than reliability, if you have a cheap switch that turns to mains water when a tank empties. Even with less than 100% reliability (day-to-day), small tanks will certainly save substantial water over a year, because any rainfall will add water to them.

In Melbourne, just a two-kilolitre tank, draining a 200-square-metre roof, connected to toilet and laundry would save a family of two to three over 50 kilolitres, more than a third of their annual usage. A five-kilolitre tank, connected it to a hot-water system as well, could save over 80 kilolitres a year

Dr Chris Walsh, University of Melbourne
Dr Tim Fletcher, Monash University

Opinion, The Age, 22 June 2007.

Stormwater is a much better option than desalination.

Hundreds of gigalitres are wasted in run-off from our suburbs, writes Barry Hart and Chris Walsh.

THE Victorian Government had an excellent record on water policy — until now. This week's decision to supplement Melbourne's urban water supplies with a very expensive and energy-hungry desalination plant is a very disappointing about-face.

The harvesting of urban stormwater is a much better and more sustainable alternative to desalination.

All Australian cities, including Melbourne, produce and waste hundreds of gigalitres of stormwater each year. This resource represents a startling opportunity to help solve our water shortage while also protecting our rivers and producing just a fraction of the greenhouse emissions produced by desalination.

One of the biggest problems with stormwater is that there is too much of it. Typically, a suburb can produce five times the volume of run-off than a similar area of rural land. The roofs and roads in urban areas produce a lot more run-off because they prevent water from filtering into the ground and because they replace trees that would otherwise take up water and release it back to the atmosphere.

That excess run-off runs down the drains with every storm, collecting a cocktail of pollutants on the way. This results in our urban streams being unhealthy.

To fix the Yarra, we need to make sure that stormwater gets to the streams more slowly. The filtration systems that are becoming more common on our streets, and are now mandatory in new developments, will assist in holding up this run-off.

But these filtration systems will work well, and provide a clean, reliable flow between rain events, only if we prevent the very large amounts of stormwater getting into them.

The best way to do this is to use rainwater tanks to capture as much run-off from our roofs as we can. But capturing roof run-off in rainwater tanks will not be effective unless this is well managed. It will be crucial that the water is used year-round, for example by plumbing the tanks into appliances such as toilets and washing machines. Use of the rainwater on gardens is also effective.

Climate change predictions suggest that rainfall will become less frequent and less reliable, and this will mean stormwater run-off will become even more important as a water resource.

The drier our catchments become, the more rain it will take to generate run-off from natural catchments and fill the dams. In contrast, a house roof will generate run-off after even a very small amount of rain, no matter how dry it has been.

A recent report commissioned by the Australian Conservation Foundation showed that domestic rainwater tanks can be a large addition to Melbourne's water supplies, at a comparable cost per litre to desalination, while using less than a fifth of the energy.

We believe that a proper economic assessment would show that the river health and other benefits of rainwater tanks would make them a better alternative water resource than desalination.

It is a great pity that the Government did not consider dispersed stormwater harvesting seriously as an alternative for Melbourne's water supply. There was consideration of harvesting water from the Yarra at Dights Falls after storms.

But such a centralised scheme would produce no stream health benefits. The damage is already done to the river and its tributaries by the time the stormwater has reached Abbotsford.

Fixing the Yarra will require dispersed stormwater treatment measures, including rainwater tanks, across the catchment. In doing so, the volume of water that could be harvested from residences alone is huge.

If the Government were to take this option seriously, there are even greater volumes of water that might be harvested from the expanses of commercial and industrial roofs across Melbourne.

In fact, Melbourne produces enough excess stormwater run-off that we might even be able to use that pipeline across the Great Dividing Range to supplement irrigation supplies in the Murray-Darling basin.

It is not too late for a policy rethink on desalination.

Professor Barry Hart chairs the Yarra Co-ordinating Committee and Water Studies Centre at Monash University.

Dr Chris Walsh is a senior research fellow there.


Opinion, The Sunday Age, 22 January 2006.

Stormwater and the Yarra

The $20m pledged in the Yarra River Action Plan to implement stormwater management plans is a good first step towards a healthy river, but much more needs to be done. The $1m for tracking down cross-connections between the sewerage and stormwater systems is a necessary first step, but it is not a long-term solution: as we find each leak in our flawed stormwater system, our ever-changing suburbs are likely to spring new leaks. To save the Yarra we need two long-term fundamental changes: to the way our city is built and to the way we think about stormwater.

The design of our stormwater drainage system guarantees a sick Yarra. It sends every drop of water off our houses and roads into the nearest stream, even on dry days. So if someone washes a car on the street, the river gets the suds; if someone connects a toilet to the stormwater, sewage flows to the river every time the toilet flushes. The system ensures that if any of the million people in the urban Yarra catchment does anything silly anywhere, the river will pay.

We don’t need a system that drains water from the catchment when there is no flood risk. New approaches to stormwater drainage keep water in the catchment until flooding becomes a risk. Retained water can be used to help with water conservation and be allowed to soak into the ground to feed our rivers more naturally. We can replace our existing stormwater infrastructure with retention systems for little cost over the next 50-100 years, as it wears out. With retention systems in place, illegal connections to stormwater will soon become apparent, because the stink will stay in the neighbourhood. What better incentive to do the right thing?

The Action Plan’s stormwater management plans are only a small, tentative step in the right direction. If the stormwater system is to change across the city, we need to change. We are all part of the problem, and we can all help. Do you know if your toilet drains to the sewer; if your roof drains to the stormwater system? How much rain is retained on your property before it drains to the stormwater system? Perhaps more money could be spent helping the community own the problem and become part of the solution.

Dr Chris Walsh, Monash University


Opinion, The Age, 4 April 2003.

Who's afraid of greenish Libs?

It is encouraging that Alan Moran (Opinion, 3/4) believes that the Liberal Party's policies have to be influenced by research.  It is a shame that his opinions on the state of the environment appear to be free from such constraints. 

Dr Moran’s claim that water quality is at its best for 50 years is at best a highly selective interpretation of monitoring data and at worst just plain wrong. 

His view of the unprecedented productivity and attractiveness of the Murray is entirely at odds with current ecological predictions of a much-degraded future for the Murray-Darling system without careful management of flows and land use. 

His claim that the places in which the  'environment has gone backwards' are usually the national parks is plainly ludicrous.  (In fact, if we were to take the health of our streams as an indicator of the condition of our catchments, streams that drain national parks are invariably among those in the best condition.  The greatest threats to water quality and stream condition are poorly planned, unregulated land uses: for the most part on private land.  The future condition of our catchments, waterways and coastal waters depends on careful planning and wise stewardship of the land.) 

Given Dr Moran's agenda for deregulation, his nervousness at the policy directions chosen by Mr Doyle is understandable.  Effective environmental management and deregulation are not comfortable bedfellows.

Dr C. J. Walsh, Water Studies Centre, Monash University


Opinion, The Age, 11 January 2001.

The Yarra clean-up is far from finished.

The aim of the EPA to have people swimming in the whole of the Yarra by 2008 is admirable.  However, when an article can be written on the state of the Yarra (‘The Age’ 9/1) without mention of urban stormwater, the greatest threat to the Yarra, it is difficult to share their optimism.

The Yarra is in better condition than it was 30 years ago, primarily because of the gradual connection of most of the metropolitan area to the sewerage system during the 1970s and 1980s.  Big problems remain, and, as Melbourne expands, big investments and greater community awareness are required to prevent them getting worse, let alone to improve them. Toxicants, such as heavy metals, and litter were highlighted. A third concern should be added: high nutrient levels, particularly during floods, which pose a serious threat to the health of Port Phillip Bay.  These three big problems all largely arise from the same source: urban stormwater. 

Melbourne has an excellent stormwater drainage system, which efficiently drains rainwater from the catchment.  Unfortunately the system also efficiently washes pollutants that build up on hard surfaces straight into our streams.

By most measures, the Yarra is in good condition upstream of Warrandyte.  There is a sharp decline in several ecological indicators downstream of Mullum Mullum Creek.  Concentrations of heavy metals are high in some places, namely the lower reaches, where the cumulative effect of urban stormwater is greatest, and the ecological condition of the river is worst.

Little evidence exists to support the assertion that Yarra platypus numbers have risen in the last century.  How many platypus lived in the Yarra downstream of Templestowe, or in Merri, Darebin, Moonee Ponds, and Gardiners creeks 150 years ago?  Nobody knows, but my guess is a lot more than the near zero to be found today.

To achieve the EPA’s aim of a swimmable Yarra within 7 years, new developments in the catchment will need to be regulated and designed to minimize stormwater impacts.  Existing stormwater systems are in need of re-engineering to reduce pollutant loads.  The Victorian Government’s allocation of $22.5 million for the Stormwater Action Program for the state, is a good start.  However, improvement of the Yarra River, perhaps just prevention of further degradation upstream, will require a much greater investment of capital and political will.

Chris Walsh, Cooperative Research Centre for Freshwater Ecology, Monash University