Measuring forestry’s impact on water availability

Undertaken by a team of CSIRO Water for a Healthy Country Flagship scientists for the National Water Commission (NWC) and Forest & Wood Products Australia, the project developed modelling tools to provide greater confidence in estimating the impact of new plantations on catchment stream flow.

Australia’s blueprint for water reform – the National Water Initiative (NWI) – recognises that a number of land-use change activities have the potential to intercept significant volumes of surface and/or groundwater now and in the future.

The Commission commissioned CSIRO to develop tools that can be used by governments to meet their agreed interception commitments under the NWI and assess the impacts of large-scale forestry plantations on water availability.

The tools assist governments to identify threshold levels to trigger planning, management and/or regulatory measures to appropriately account for forestry plantation water use.

“Climate, vegetation, soil, geology and other features can all combine to make a difference to how much water finally flows into streams,” said project team leader, CSIRO’s Dr Mat Gilfedder.
 
Dr Gilfedder’s team focused initially on improving the confidence in the modelling approach by analysing measured data from 16 catchments around Australia.

“From this we were able to see that plantation expansion has had an impact on catchment streamflow,” Dr Gilfedder said.

The team also developed modelling tools that can account for variability in tree growth and management, such as planting date and location, as part of a catchment water model. These tools can be used to help predict the variation in impact on catchment stream flows of changes in plantation area scenarios.

“The work gives us a better understanding of the impact that plantations can have on local and downstream water supplies, particularly how that impact is likely to vary depending on location within a catchment.”

The research will help forestry industry, water resource managers, catchment managers and government agencies to manage the impacts of plantations on water availability.