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Perth

                                                                                                   

Water Overview

                             

A summary of the significant water events, major water initiatives and improvements in water information occurring during the reporting period are explained.

 

Water overview 2009-10

Significant water events

There were no significant water events in the region during the reporting period. 

 

Streamflow during 2009-10

There are three primary river systems within the Perth region: Swan-Canning, Murray and Harvey.
 
During 2009-10, total annual flow in the Swan River was 272 GL, which is above the mean annual flow of 244 GL. Total annual flow in the Murray River was 318 GL, which is also above the mean annual flow of 268 GL. The above average flows in these catchments can be attributed to well above average monthly flow volumes observed along these rivers during the wet months of July, August and September (Figures W1 and W2). The high flows during this three month period reflect the relatively high rainfall that occurred across the region during this period (see Figure C4 in Climate Overview).
 
However, total annual flow during 2009-10 in the Harvey River was 86 GL, well below the mean annual flow of 148 GL. Flow was below the 50th percentile in all months except September 2009 (Figure W3).

Figure W1. Graph of total monthly flow along Swan River during 2009-10 compared with long-term percentiles

Figure W1. Graph of total monthly flow along Swan River during 2009-10 compared with long-term percentiles

Figure W2. Graph of total monthly flow along Murray River during 2009-10 compared with long-term percentiles

Figure W2. Graph of total monthly flow along Murray River during 2009-10 compared with long-term percentiles

Figure W3. Graph of total monthly flow along Harvey River during 2009-10 compared with long-term percentiles

Figure W3. Graph of total monthly flow along Harvey River during 2009-10 compared with long-term percentiles

 

Major water initiatives

The region has experienced a decline in rainfall over the past 30 years (Department of Water, 2009b). During that time, rainfall has declined by more than ten percent during the average wet season (May to October). The result has been a 50% reduction in streamflow into the public water supply reservoirs and a substantial reduction in aquifer recharge (Department of Water, 2009b). As a result, a number of major water initiatives are being pursued in the region, including:

  • Gnangara Sustainability Strategy
  • Perth-Peel Regional water plan
  • construction of a second desalination plant.

Gnangara Sustainability Strategy

The Gnangara Sustainability Strategy is an action plan that ensures the sustainable use of water for drinking and commercial purposes and to protect the environment on the Gnangara water table aquifer. The strategy is an interagency initiative developed by the Department of Water in conjunction with the Department of Agriculture and Food, Department of Environment and Conservation, Department of Planning, Forest Products Commission, Water Corporation and CSIRO.

The strategy was open for public comment during the 2009-10 reporting period. The final plan was delivered to the Minister for Water Resources for consideration.

Perth-Peel Regional water plan

The Perth-Peel Regional water plan (Department of Water, 2009b) is being developed to set the strategic directions for the sustainable management of the region’s water resources. The plan describes techniques that can be used to conserve and manage the water resources in the region, such as:

  • reducing water demand by using water more effectively and efficiently
  • facilitating the use of alternative sources of water supply
  • restoring and protecting waterway and wetland health.

The plan was open for public comment during the 2009-10 reporting period. The final plan was revised and submitted to the Minister for Water Resources for approval during 2010-11.

Desalinated water

The Water Corporation is in the process of constructing the Southern Seawater Desalination Plant near Bunbury, which is just below the Perth region boundary. It is due for completion in 2011 and will more than double the current supply of desalinated water to the Perth metropolitan area. This water resource is part of the Water Corporation’s long-term water security solution for the Perth region as outlined in Water Forever (Water Corporation, 2009).