15 per cent reduced average annual rainfall / Managing groundwater

By planning future water allocation we will be able to provide certainty about any changes needed, allow plenty of time to adjust and keep the changes small.

We take seriously the evidence of climate change and its effects on groundwater resources. As a result of climate change, since 1975 the south-west of Western Australia has experienced a 15 per cent decline in average annual rainfall. This has reduced recharge to groundwater aquifers from Geraldton to Esperance.

Across much of the south-west corner of the state, groundwater is an important part of the water supply mix and is used for town drinking water supplies, to irrigate public open space and for irrigated horticulture. Perth’s groundwater resources provide more than 40 per cent of scheme supplies to households and businesses, almost all of the water supply used for parks, sports grounds and agriculture, and one in four domestic gardens. Groundwater also plays an important role in our natural environment by supporting wetlands, lakes and deep-rooted vegetation.

Managing groundwater sustainably to provide for our current needs and for future generations means making sure the amount of groundwater pumped from aquifers stays in balance with the amount of recharge to groundwater aquifers from rainfall. The amount of groundwater available for use in each location is identified through the department’s water allocation plans. To get this right, water allocation planning involves considerable science, including future climate projections.

Water allocation planning responds to climate change by using the projected climate trend to identify water availability over the 10 year life of the plans. Because rainfall in the south-west is decreasing, in many cases this means that no more groundwater can be made available for use. Water users respond to climate change by using the water that is available more effectively including through improving irrigation technology, better design of green space, reducing leaks and wastage, and through water trading. Looking ahead, in some locations we will need to begin to reduce groundwater use as rainfall decreases. By planning future water allocation we will be able to provide certainty about any changes needed, allow plenty of time to adjust and keep the changes small.

In the next few years we aim to complete or progress groundwater allocation plans for Cockburn, Gnangara, Gingin, Myalup, Perth South and Jandakot, Serpentine and Albany.

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