Water savings from willow removal

April 20th, 2018

The Challenge

Water scarcity is guaranteed into the future, especially in semi-arid and arid environments and in riparian systems, flow alterations open up the way for invasion by weed species. Willows are an invasive species to Australia that were introduced by Europeans in the 1800’s. Since that time they have spread, out competed native riparian vegetation and reduced the flow of water in streams and creeks. Anecdotal evidence suggests that willows also use a considerable amount of water in comparison to native species.

During the Millennium drought, water savings projects were sought in the Murray-Darling Basin that would potentially return water to rivers. Funding became available through the Commonwealth Government to investigate if water savings could be made from willow removal. Water saved would then be returned to creeks and streams to improve ecological condition and to support downstream users in small communities.

Willows along the River Murray in South Australia

Willows lining the River Murray in South Australia. PHOTO: Tanya Doody

Our response

  • Our capability

CSIRO Land and Water maintains a large store of field equipment to undertake such research in the most robust way possible. Other organisations generally deploy 3-4 sensors for an experiment, however CSIRO have to capability to deploy 10 times that amount, to ensure the most accurate results possible are achieved. Demonstrated expertise also exists within CSIRO.

  • Science and Innovation

This CSIRO project undertook research to measure water use and determine water savings using sapflow sensors and field collection of soil and water evaporative losses. Additional management tools were developed through evaporative modelling and remote sensing, to allow users to understand water savings from willow removal in their climatic zone. A remote sensing tool to map willow area, allows accurate calculation of water savings in a catchment, based on a quantified method to robustly map willows.

Results

The research conducted on water savings from willow removal by CSIRO, underpins willow management plans in South Australia, New South Wales, the Australian Capital Territory and Victoria. Such research had not been undertaken in the past. Estimates from Greening Australia, indicate that 87,000 ha of willows were removed in 2016. With potential water savings of 5.5 ML ha, a medium estimate of 30 GL of water could be saved with willow removal that year. In relation to the general water security market, this might equate to ~$16M in water entitlements. The value of this research has also been recognised internationally in South Africa and New Zealand, with researchers undertaking similar work. This research is also being recognised as a ‘complementary measure’ to produce water savings within the Murray-Darling Basin Plan.

Key outcomes

  • Willows are high water using invasive species in Australian streams. The four year study demonstrates substantial water can be saved if willows are removed from water courses, in semi-arid climates.
  • Easy to use tool allows water managers to estimate how much water can be saved per hectare of willow canopy removal for any climate zone across south-eastern Australia.
  • Removal of willows can be expensive. A new innovative willow mapping method allows water managers to undertake cost-benefit analysis related to value of water saved and cost of willow removal.
Sensor in willow tree to measure how much water willows use

Sapflow sensor measuring willow water use in a willow tree in Myrtleford in New South Wales. PHOTO: Tanya Doody

Contact Person

Dr Tanya Doody

Additional information

  • Doody TM, Benyon RG. 2011. Quantifying water savings from willow removal in Australian streams. Journal of Environmental Management, 92, 926-935.
  • Doody TM, Nagler PL, Glenn EP, Moore GW, Morino K, Hultine KR, Benyon RG. 2011. Potential for water salvage by removal of non-native woody vegetation from dryland river systems. Hydrological Processes, 25(26), 4117-4131.
  • Doody TM, Benyon RG, Stewart L, Koul V. 2013. Development of pan coeffecients for estimating evapotranspiration from riparian woody vegetation. Hydrological Processes, 28(4), 2129-2149.
  • Doody TM, Lewis M, Benyon RG, Byrne G. 2014. A method to map riparian exotic vegetation (Salix spp.) area to inform water resource management. Hydrological Processes, 28(11) 3809-3823.
  • Willow research in detail
  • ECOS article