Print this page as a project information sheet

Regional planning context and future land-uses

As part of the Gnangara Sustainability Strategy, the Department for Planning and Infrastructure is undertaking the following project:

The project

Future land-uses

Possible land-use change on the Gnangara Mound in the medium- to long-term is only an option if there is:

  • a proven net environmental, social and economic benefit; and/or
  • a significant change in the current government policy, statutory regime and government position on the role of the Gnangara Mound as a water future water source for Perth to justify a change in the defined boundaries of the Underground Water Pollution Classification Control Area (UWPCA) and Priority 1, 2 and 3 source protection area boundaries.

These boundaries were included in the Metropolitan Regional Scheme (MRS) in 2004 (MRS Amendment 1076/33) to protect the UWPCA public drinking water source from possible contamination from inappropriate land-uses. They were ratified recently.

There is a wide range of state and local government planning and environmental policies that regulate land-use and development over the Gnangara Mound. Future options depend on a full understanding and review of all the strategic and statutory policies that govern land-use planning on the mound.

The outcomes of the other GSS projects into the hydrogeological and biodiversity resources and values of the mound will also provide essential information on the feasibility of alternative land-uses.

Soil and groundwater quality

Important issues to consider in terms of groundwater quantity and quality and the links to land-use planning and development are:

  • The role of natural and climate change variability in changing groundwater quantity and quality across the superficial aquifer.
  • The role of the pines and pine harvesting on future groundwater quantity and quality.
  • The role of drained or falling water levels in exposing sulfidic material to oxidation, acid generation and metal mobility and implications for the Gnangara ecosystem and future land-uses.
  • Can land-use change be used to improve recharge into the mound and what land-uses may have net beneficial effects?
  • Would limited future sustainable urban development provide benefits for groundwater recharge, wetland water quantity and quality management and/or other benefits?
  • How can total water cycle management principles and innovative urban design principles be applied to potential land-use change to achieve net benefits for the Gnangara system?

Appleyard and others (2004; 2006) documented the increased impacts on groundwater quality of the disturbance of sulfidic materials, urbanisation and a drying climate. The increased store of aluminium in podsolised soil profiles beneath pines has also been investigated recently (Troy Cook - personal communication). Acidification of shallow groundwater and lake systems has also been reported.

Quantifying the onset of these processes and their impacts and management is not well established. Specific investigations are needed to:

  • unravel natural changes from those due to human use
  • provide information to determine future land-use change opportunities and constraints with respect to protecting groundwater quantity and quality.

Our approach will be to investigate processes within an identified, impacted land-use area(s): particularly areas affected by disturbance and oxidation of sulfidic aquifer and wetland sediments.

What will the project achieve?

Primary objectives are to:

project1 image

  • Review current state and local government policies and strategic land-use and infrastructure planning over the Gnangara study area.
  • Provide an overview of the Gnangara System study area in the context of land-use planning policies, environment and water planning policies and frameworks.
  • Consider strategic planning and policy issues in relation to future potential land-use change and, taking into account the outcomes of other GSS projects, review possible alternative land-uses for identified areas of State Forest 65 and relevant surrounding areas after removal of pine plantations.
  • Investigate how land-use change can be used to improve recharge into the mound and what land-uses may have net beneficial effects.
  • Understand the processes affecting acidification of shallow groundwater and connected lakes (potential and actual occurrences are apparent in the superficial aquifer) and develop an objective methodology to distinguish between 'natural' acidity and that caused by human activity or climate change. In particular, determine and quantify the processes governing the acidification of groundwater from oxidation of sulfidic material (sulphur with one other element) exposed by disturbance or water table reductions.
  • If necessary, carry out more detailed site analysis and concept planning (conceptual spatial structure planning) of specific areas identified for possible future alternative land-uses.
  • An intensive and targeted investigation of hydrogeological and geochemical processes within a prescribed land-use area will be conducted. The area chosen will be one of those under consideration for land-use changes by the Western Australian Planning Commission.

For more information on these and other projects, please contact us at gss@water.wa.gov.au