The Essential Services Commissioner for Victoria has announced that the price of water will soon increase 40-60%. Minister Tim Holding said there will be a further rise in the price of water of $100 per household per year, equating to hundreds of millions of dollars. He cites the drought and global warming as the principle reasons.

The cost of water will continue to rise with the cost of electricity to pump the water and the cost of maintaining desalination plants. The same Minister confirmed that Melbourne was moving away from “catchment based management”.

What was catchment management — just before we lose it?

For domestic and agricultural water dams have been constructed well above towns and, where possible, with bush catchments. Bush catchments provide the cleanest water and the most reliable flow when there is no rain.

With the recent spate of bushfires, bush is being cleared now right across Victoria. The older among us can all remember the time when people washed concrete driveways with water. When the hose stopped the flow into the gutter would slow and stop as the last of the water ran from the distant part of the driveway to the gutter. This is the equivalent to a concrete or asphalted catchment and shows how little value such catchments have.

Where there is bush, the water is soaked into the ground and, in the heaviest rain, follows the roots of the trees into the various aquifers, layers of permeable soil/sediment, where it eventually discharges downstream.

Eucalypt leaves are most often sickle shaped. This enables even water gathered from mist or condensation from the morning pre dawn chill to flow to a pointed tip, creating a droplet with sufficient weight to penetrate the leaf litter. Trees use water to grow, which explains why they have evolved to efficiently catch and store rain water in forested aquifers — there are no puddles in the undisturbed bush when it rains.

The age of the trees obviously determines the size of their root mass and just how many aquifers they charge up. The old forests that survived have developed these strategies to keep growing through the longest droughts over millions years.

Trees use water too and transpire it into the air from their leaves. The misty clouds that rise from the forest are evidence of this. These clouds contribute to rainfall locally and elsewhere. As the breeze and sun evaporates water the air is cooled. This “transpiration” from forests cools the air, which is why they are cool places to be on a hot day. Warm air that blows through forests can hold more moisture and when it is chilled it forms clouds or rains.

When the bush is burned there is little or no transpiration for years, reducing the rainfall locally and regionally.

The Victorian Minister for Water has likely heard none of this. He has been advised that the reduced rainfall Victoria is experiencing is due to global warming — not that past clearing and fires have dried the landscape and reduced water quality, streamflow and rainfall. There is lack of analysis of the wealth of historic rainfall and streamflow data.

Since water restrictions in Melbourne have lead to the death of millions of gardens and the drying out of the landscape, the rainfall for Melbourne itself has declined.

If the Royal Commission into the Victorian bushfires must surely examine the impact on vegetation, rainfall and streamflow, water quality and streamflow persistence if they are going to recommend increased use of fire.

Peter Fray

Fetch your first 12 weeks for $12

Here at Crikey, we saw a mighty surge in subscribers throughout 2020. Your support has been nothing short of amazing — we couldn’t have got through this year like no other without you, our readers.

If you haven’t joined us yet, fetch your first 12 weeks for $12 and start 2021 with the journalism you need to navigate whatever lies ahead.

Peter Fray
Editor-in-chief of Crikey

JOIN NOW