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Author Topic: Willows and water  (Read 2721 times)

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Willows and water
« on: December 16, 2010, 11:28:51 AM »
Willows and water

Willows are a recognised problem for waterways and fish in Australia. As well as affecting water quality, they also transpire a lot of water. Recent research has shown that willows growing in]stream in permanent water have the potential to extract more water than that lost through open water evaporation from rivers, streams and creeks in Australia. Removing willows in these circumstances could lead to net water savings of 5.5 ML per year per hectare (area covered by the treesf crowns).
Therefore the replacement of instream willows with native riparian vegetation will improve habitat for native fish and also save water.

To read more of this work by Doody and Benyon go to: http://dx.doi.org and type in: doi:10.1016/j.jenvman.2010.10.061



Source: Newstreams publication


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Water savings from willow removal - CSIRO
« Reply #1 on: February 17, 2012, 11:37:43 PM »
Water savings from willow removal - CSIRO



Weeping willows lining the banks of the Murray River at Mannum, South Australia

CSIRO research has shown that replacing in-stream willows with native vegetation helps save water.

Background
Weeping Willows (Salix babylonica) are widespread along channels of the Murray-Darling Basin, especially in the temperate zone.

They were planted in the late 1800s and early 1900s along the river and creeks to aid in bank stabilisation and to provide shade. Willows were also planted along the Murray River channel to mark the channel in times of flood and to aid paddle steamer traffic.

Since then they have spread widely along creeks and streams in south eastern Australia.

While willows modify native ecosystems and clog streams with fine root masses, they can also consume and transpire large amounts of water.

This is important in drier regions where regulated streams deliver water for irrigation. However, little data is available on the amounts of water that willows actually use.

Project objectives
Researchers from CSIROs Water for a Healthy Country Flagship set out to quantify the amount of water removed from streams by weeping willows and to compare this with the water use of native red gums, in the Yanco Creek system, New South Wales. The climate is semi-arid with an average annual rainfall of approximately 350 mm.

With a well established water market, and the water price likely to reflect the true value of a water entitlement in the long term, knowledge of the volumes of water lost to transpiration and evaporation is extremely important to resource managers for example, determining the net benefit of willow control programs in both water and monetary terms.

The approach
In a three-year field research study from 2005 to 2008, CSIRO scientist Ms Tanya Doody and her colleague Dr Richard Benyon from the University of Melbourne, set up sap flow sensors in:

willows with easy access to stream water (in-stream willows)
willows further away from the stream (bank willows)
adjacent river red gums, to determine total evapotranspiration.
Of the willows species, only weeping willows were present. Other measurements of local water balance components were made, with data collected over the willow growing season from September to May. Evapotranspiration components were inferred over the winter months to determine 12 months estimates of total evapotranspiration.

The research concluded that removing in-stream willows may potentially save 5.5 ML per year per ha of willow crown projected canopy area.Results
Whilst red gums and willows, without permanent access to water, had relatively low levels of water use (on average 1.51 mm per day for red gums and 1.54 mm per day for willows), willows with permanent access to the stream could use on average up to 5.6 mm per day compared to 4.08 mm per day for open water evaporation.

Quote
     "The research concluded that removing in-stream willows may potentially save 5.5 megalitres per year per hectare of willow crown projected canopy area as well as promote improved stream flow and water quality."     


It also found that replacing in-stream willows with river red gums would not lessen the water savings, a finding that will encourage rehabilitation efforts.

The research also noted that the removal of bank willows created no water savings, but that catchment managers might consider their removal if the aim is to reduce the likelihood of future spread.

This means that one hectare of in-stream willows with permanent access to stream water consumes an average of 20 megalitres of water per year over the three measurement years based on crown projected willow canopy area.

At 2010 market prices for high-reliability water entitlement of A$2000 per megalitre (a high-reliability water entitlement will allow extraction of 100 per cent of entitlement to be available about nine years in ten) that water saving is worth over A$11 000. In addition a farmer will pay about A$40/ML to use their entitlement, meaning the annual value of water used by a willow accessing stream water is about A$200.

Since in-stream willows are known to occupy over 300 ha of stream bed/banks along regulated streams in NSW and Victoria, this means a water saving of approximately 1500 megalitres. This saving is worth about A$3 million and represents about A$60 000 in usage charges.

Future work will quantify water savings from different willow species in a cool climatic zone.

Data collected across four years of measurement and the Penman-Monteith model will be used to develop the potential to estimate water savings across different climatic zones in Australia using pan coefficients (crop factors).

This will allow resource managers to readily quantify the water savings from willow removal programs in their own area, and aid with preparation cases for ecological restoration.

Ms Tanya Doody conducted this research as part of her doctoral work through the University of Adelaide. Read more about Ms Tanya Doody: investigating vegetation health and water use.

Read the journal paper Quantifying water savings from willow removal in Australian streams [external link].


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Re: Willows and water
« Reply #2 on: February 18, 2012, 01:11:27 PM »
okay the willows may be bad but geez the cod like to hide under or near them..lol

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Re: Willows and water
« Reply #3 on: February 29, 2012, 12:51:03 AM »
okay the willows may be bad but geez the cod like to hide under or near them..lol

Good point Brett.
If we were to replace a willow with a similar size native tree do you reckon a cod might still be sitting under it?

What I mean is, do you think the cod prefer a willow to a bottle brush or gum tree?

Cheers,

fitz..

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Re: Willows and water
« Reply #4 on: February 29, 2012, 07:46:10 AM »
bottle brush ..yeh caught both cod and bass/toga from these...think the fish like the safety of a low overhanging or in water tree /bush...more hidey holes/roots they can dart from quickly.. so more bottle brush and less willow the cod will go to the bottle brush for sure..as i said when theres no willow i always go to the next best bush...:youbeauty

 

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