Institute of Forestersof Australia

Forest Management and the impact on

Water Management

ScienceHistoryFuture

Forest Management and Water Management

• All land is in a catchment Warning: Science Content

Forest Management and Water Management

• Forests and trees do play a key role in catchment behaviour

Forest Management and Water Management

• Forest Hydrology Research has given some answers

Forest Management and Water Management

• Forest Hydrology Research has given some answers

Forest Management and Water Management

• Forest Hydrology Research has given some answers

Forest Management and Water Management

• How do Mountain Ash Forests grow and flourish?

Forest Management and Water Management

The trigger for Mountain Ash forest renewal is wildfire

Wildfire provides • Heat to open fruit capsules immediately after the fire • Ash bed seed bed with access to mineral soil• Removal of competing vegetation• Removal of canopy to allow additional light to soil surface• Removal of aleopathic responses • Flush of nutrients in ash for early growth

Forest Management and Water Management

The History of the Mountain Ash forests in

Melbourne’s Water Catchments

1600 20061800 1939

Wildfires burn through the ranges east of Melbourne and a seedling forest of Mountain Ash

is established. One of these seedlings will become the giant Furmston’s Tree.

1730

Wildfires burn through Wallaby Creek. The resultant forest of Mountain Ash is now known as the “Big Ash” containing some of the tallest trees

in Victoria.

1851

Black ThursdayA great fire sweeps across a thinly populated

Victoria

Red Tuesday12 people die and 1500 homes lost as fire sweep

through the Gippsland forests

1898

Melbourne sources its water from theYarra River above Dight’s FallsMelbourne builds its first dam

at Yan YeanMelbourne establishes a series of forested

closed catchments where all uses other than water production are banned. Wallaby Creek, Maroondah, O’Shannassy and Upper Yarra.

1933Furmston’s Tree Discovered

Harold Furmston discovers a magnificent mountain ash on Mount Monda, near

Healesville.

It is carefully measured and found to have a girth of 19.5 metres. The tree is named

after its discoverer: Furmston’s Tree.

The Healesville Shire President soon leads an excursion to the base of the celebrated giant, and bushwalkers make pilgrimages

to it.

Not only are the mountain ash forests greatly admired for their awesome beauty

– they have now become the most economically valuable forest tree in

Victoria.

Forest Management and Water Management

The History of the Mountain Ash forests in

Melbourne’s Water Catchments

1600 20061800 1939

Wildfires burn through the ranges east of Melbourne and a seedling forest of Mountain Ash

is established. One of these seedlings will become the giant Furmston’s Tree.

1730

Wildfires burn through Wallaby Creek. The resultant forest of Mountain Ash is now known as the “Big Ash” containing some of the tallest trees

in Victoria.

1851

Black ThursdayA great fire sweeps across a thinly populated

Victoria

Red Tuesday12 people die and 1500 homes lost as fire sweep

through the Gippsland forests

1898

Melbourne sources its water from theYarra River above Dight’s FallsMelbourne builds its first dam

at Yan YeanMelbourne establishes a series of forested

closed catchments where all uses other than water production are banned. Wallaby Creek, Maroondah, O’Shannassy and Upper Yarra.

Black FridayMassive fires sweep through the catchments

killing large areas of Mountain Ash and establishing regrowth forests

Melbourne Board of Works notice reduced water yield from catchments.

Commission major hydrological studies and catchment monitoring network.

Relationship between water yield and forest age determined and policies adopted to

exclude fire from all catchments.

Catchments declared as National Parks giving water and conservation objectives.

Only Thomson and Yarra Tribs. remain with multiple use objectives and are open for

visitors.

2000The Furmston Tree collapses

at the end of its life

Great Dividing Range Fires burn to the edge of the catchments and strategic firebreaks established to

prevent fires entering the catchments.

Period of successfully excluding wildfire from Melbourne’s water Catchments

Forest Management and Water Management

Future of Melbourne’s Water Catchment Management

• The forests contain a range of age classes resulting form the wildfires or harvesting . They range from 277, 156, 109, 68 and 26

or less.

• Periodic catastrophic Wildfires are a natural part of the ecosystem.

• Forests in the open age catchments have a broader range of age classes providing greater diversity.

Forest Management and Water Management

Future of Melbourne’s Water Catchment Management

• The Thomson catchment is dominated by 1939 regrowth.

• 68 year old forests are beginning to increase water yield.

• 120 ha per year is harvested and regenerated.

• It will take a further 100 years to harvest the 40% that is available.

• The average age and the water yields are increasing.

• The water yields lost due to harvesting are the potential gains not realised.

Forest Management and Water Management

Future of Melbourne’s Water Catchment Management

The next big wildfire will:

• Drastically reduce water quality for a 2 to 3 month period where water from burnt catchments will need to be stored or diverted.

Additional water treatment may be required.

• Provide large areas of regrowth forest that will reduce water yields over the next 10 to 70 years.

The catchment research has shown that thinned regrowth can increase water yields.

Thinning would normally not be allowed in National Parks and would only be an option in the open catchments.

Forest Management and Water Management

What is being done elsewhere?

• WA Water Corporation has adopted Security through Diversity water supply policy.

• Wungong catchment is 13,000 ha of dry sclerophyll forest.

• By Spending $20M on active forest management including thinning and ecological burning water yields can be increased.

• Water yields will be monitored and are expected to increase by 4 to 6 Gl per year. This is a 25% increase.

• The cost of treatment is very competitive at 23 cents per kilolitre compared with desalination at $1.15 per kilolitre.

Forest Management and Water Management

Sources

• Dr Rob Campbell Fire Cycle Booklet (unpublished)

• Dr Rob Campbell Streamflow Booklet (unpublished)

• ABC Black Friday - Online documentary about 1939 Victorian bushfires.

At abc.net.au/blackfriday/

• Batani Frank, Bradshaw Jack, Roger Underwood. (2007) Managing forested catchments for water, timber and

biodiversity. ANZIF Conference Proceedings