This action is to improve understanding about the impact of land use changes on water use and the capability to estimate and report on these interactions. New technologies (such as satellite imagery and remote-sensing) are improving our understanding of how changes in land use affect water resources, and the importance of this understanding is increasingly recognised. In 2011–12, the National Water Commission funded the (then) Department of Sustainability and Environment (DSE) to prepare the groundwork to regularly estimate and report on water use by land use.
This work included estimates of evapotranspiration, which is a key water use in vegetated landscapes. DSE contracted consultants to provide the tools and guidance to make evapotranspiration estimates, and they are now made annually using Victorian Land Use Information System land use data. However, water use estimates are only reported at a whole-of-basin scale, and they are not broken down by land use category or land use change.
While land use and vegetation cover will influence evapotranspiration, climatic conditions have a larger impact on changes in evapotranspiration.
Given this, the estimates of evapotranspiration in the Victorian Water Accounts will continue to use climatic information as the basis for annual reporting of evapotranspiration.
Since 2011, drivers for land use change across Victoria, particularly relating to the development of plantation forestry, have changed. Plantation areas across Victoria have been generally steady for the past decade.
Changes in land use will be tracked using available information, such as the 5-yearly State of the Forests report, which reports the area of plantation forest across the State.
Estimates of evapotranspiration will incorporate land use changes on a 10-yearly basis. This timing aligns with the commitment to review the net take from plantation forestry in Victoria’s WRPs under the Basin Plan. More frequent updates may be undertaken if significant land use changes are identified in the intervening period.
DEECA to estimate evapotranspiration in the Victorian Water Accounts based on annual climatic conditions. Land use changes will be incorporated periodically, to align with other reporting obligations, such as the 10-year review of the Basin Plan.
Action status (5-yearly assessment): Partly or not yet achieved
Delivery period: NA