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Institute of Foresters of Australia. Forest Management and the impact on Water Management.

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Presentation on theme: "Institute of Foresters of Australia. Forest Management and the impact on Water Management."— Presentation transcript:

1 Institute of Foresters of Australia

2 Forest Management and the impact on Water Management

3 Science History Future

4 Forest Management and Water Management All land is in a catchment Warning: Science Content

5 Forest Management and Water Management Forests and trees do play a key role in catchment behaviour

6 Forest Management and Water Management Forest Hydrology Research has given some answers

7 Forest Management and Water Management Forest Hydrology Research has given some answers

8 Forest Management and Water Management Forest Hydrology Research has given some answers

9 Forest Management and Water Management How do Mountain Ash Forests grow and flourish?

10 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

11 Forest Management and Water Management The History of the Mountain Ash forests in Melbournes Water Catchments 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 Furmstons Tree 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 Black Thursday A great fire sweeps across a thinly populated Victoria Red Tuesday 12 people die and 1500 homes lost as fire sweep through the Gippsland forests 1898 Melbourne sources its water from the Yarra River above Dights Falls Melbourne builds its first dam at Yan Yean Melbourne establishes a series of forested closed catchments where all uses other than water production are banned. Wallaby Creek, Maroondah, OShannassy and Upper Yarra Furmstons Tree Discovered

12 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: Furmstons 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.

13 Forest Management and Water Management The History of the Mountain Ash forests in Melbournes Water Catchments 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 Furmstons Tree 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 Black Thursday A great fire sweeps across a thinly populated Victoria Red Tuesday 12 people die and 1500 homes lost as fire sweep through the Gippsland forests 1898 Melbourne sources its water from the Yarra River above Dights Falls Melbourne builds its first dam at Yan Yean Melbourne establishes a series of forested closed catchments where all uses other than water production are banned. Wallaby Creek, Maroondah, OShannassy and Upper Yarra. Black Friday Massive 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 The 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 Melbournes water Catchments

14 Forest Management and Water Management Future of Melbournes 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.

15 Forest Management and Water Management Future of Melbournes 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.

16 Forest Management and Water Management Future of Melbournes 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.

17 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.

18 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


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