The plan
The Murray drainage and water management plan contains principles, strategies and tools to achieve best water resource management outcomes for the Murray area. The study area comprises of a series of inter-connected wetlands, lakes, rivers and groundwater aquifers that contribute to the highly complex and internationally important hydrological and ecological system of the Peel-Harvey estuary catchment. The prevailing environmental condition of the plan area, particularly during winter, is one of excess water, coupled with limited availability of allocated water resources that are traditionally considered useable.
The plan area contains land which, if developed, could result in residential areas that are prone to seasonal inundation by shallow groundwater, significant flooding during major storm events and at risk of flooding from extreme tidal conditions and storm surges, if not effectively managed, all of which may represent substantial risk to human life and property.
Historically such areas were bypassed for urban development in favour of higher drier easier prospects.
The Department of Water considers that with sufficient initiative, effort and investment it may be possible to overcome these considerable challenges and the landscape may become suitable to support urban development from a water management perspective provided that the principles and strategies in this document are adhered to.
The draft plan was made available for public comment in late 2010. The comments and the Department of Water's responses are detailed in the Murray drainage and water management plan: Statement of response.
A DVD with the DWMP, statement of response and supporting technical studies and current Flood mapping (Oct 2011) is available from the Department of Water (Mandurah Regional office, head office) and Shire of Murray.
High Resolution Figures
Supporting technical studies
A series of technical studies have been undertaken in the study area to provide critical input for the DWMP. These studies provide the basis for the principles and strategies that will allow development to be undertaken in this highly challenging area. These studies are provided for your information and are not for public comment.
Floodplain studies
The Murray floodplain development strategy (GHD, 2010) was prepared in response to recent floodplain development issues and to inform this drainage and water management plan. It covers riverine, estuarine and stormwater flooding in the Murray study area as well as the Peel-Harvey estuary and also the Murray River from the Darling Scarp upstream of Coolup down to Pinjarra. The Serpentine River floodplain management study (SKM, 2010) undertook a similar study for the Serpentine River covering the Murray DWMP area upstream of Lakes Road.
All flood maps are available from Department of Water (Mandurah Regional office and head office).
Hydrological studies
The Murray DWMP study area exhibits a high degree of surface/groundwater interaction. This interaction and the need to determine ecological water requirements for wetlands lead to a study of both surface and groundwater aspects of the hydrological regime. This study assessed the likely impacts of climate change, development and drainage on water levels above and below the ground.
- Murray hydrological studies: Surface water, groundwater and environmental water – Conceptual model, (Hall et al, 2010a)
- Murray hydrological studies: Surface water, groundwater and environmental water – Model construction and calibration, (Hall et al, 2010b)
- Murray hydrological studies: Surface water, groundwater and environmental water – Land development, drainage and climate change scenarios report, (Hall et al, 2010c)
- Murray hydrological studies: surface water, groundwater and environmental water : acid sulfate soil risk assessment and hydrochemistry (Kretschmer et al, 2010).
Ecological water requirements (EWR) for selected wetlands
Within the DWMP study area, there are hundreds of wetlands of regional, national and international significance with approximately 80% of the plan area identified as wetland. Key wetlands have been selected to have their ecological water requirements defined, which involved a detailed assessment of the water regime required to maintain the ecological values of the wetlands.
The two critical components of the EWR study were:
Nutrient studies
Nutrification and the resultant toxic algae blooms have been an issue within the Peel-Harvey Estuary for many years. The Water quality improvement plan (WQIP) for the rivers and estuary of the Peel-Harvey system (EPA 2007) was produced to address these issues with part federal funding via the Coastal Catchments Initiative and with involvement of South West Catchment Council.
Since the WQIP, the Department of Water has undertaken more detailed modelling Hydrological and nutrient modelling of the Peel-Harvey catchment and identified applied and discharged loads of total nitrogen and phosphorous. Comparison between loads discharged from the major rivers and load targets from the have been used to derive targets for applied nutrients. Other recent work used to provide information on nutrient loads is the Survey of urban nutrient inputs on the Swan Coastal Plain.
Managed Aquifer Recharge
The Feasibility of managed aquifer recharge using drainage water study highlights the opportunity for stormwater to become an asset for local communities, as it has the potential to supply industry, public open spaces, sporting fields and private gardens. The report outlines that the confined Cattamarra Aquifer has a high potential for storage of harvested stormwater of a suitable quality.