Department of Water

Department of Regional Development

The importance of groundwater to the Blackwood and other iconic rivers of the south-west

Yarragadee and Leederville aquifers discharge into the Blackwood River near Darradup measurement station, not far from Nannup

The Blackwood, Margaret, Donnelly, Warren, ’s pools full, even during the long, and Capel rivers in the south-west of Western dry summer months. Australia play a major role in supporting local Our new findings show how the Blackwood, one of industry, agriculture, tourism and the environment. the region’s most recognised rivers, is supported Given their importance to the region, the by natural groundwater flows. The Blackwood Government of has made a $1.6 has the region’s longest section of permanent million investment made possible by Royalties for groundwater-fed flow and it uniquely displays Regions funding to better understand the rivers the reverse of typical river behaviour by being in the face of a drying climate and increasing more saline during winter than in summer. This groundwater use. phenomenon is the result of salt in the catchment For the first time, the Department of Water’s and the fresh groundwater feeding into the river. expert scientists have studied the connection Throughout the year, freshwater from the between these five rivers and the major aquifers Yarragadee and Leederville aquifers discharges of the region. In doing so, we have discovered a into the Blackwood just downstream of Nannup. number of unique attributes about the rivers and During winter, rainfall over the salt-affected underlying aquifers. headwaters of the Blackwood washes downstream and increases salinity of the flow. In summer, The discovery with less rainfall, the fresh groundwater has more We have quantified the influence that groundwater influence on the quality of the river water. has on keeping parts of the Blackwood, Donnelly, Our studies also show how the ecology of Warren and Capel flowing all year round, and the

September 2016 Securing Western Australia’s water future River flowsalinitychangesovera12-monthperiod linked to climate change. impacted by water fluctuations and use in rainfall patterns how and river’s the flow may be rivers.and define has recharge helped This it soaked into ground through and the aquifers as or tracers rainfall ‘fingerprints’ using chemical targeted aquifer river and water sampling, tracked waterA specialised study, using and rain gauges How didwedoit? after systems. to these looking rivers important is Careful management of groundwater around the theyrivers aquatic the and support. species groundwater volume will detrimental be to the Further in water decreases and quality freshwater in south west. the species fish migration of freshwater cobbler, largest the for the in summer alsoimportant is discharge intoback main the channel. groundwater The During summer river the when freshens they move Poison Gully. or Brook likefreshwater Milleannup tributaries 1999 Act Conservation federal (listedperch asa‘Vulnerable’ the under species freshwater asBalston’s such species fish pygmy differentthe levels of salinity. During winter, to in response has changed Blackwood the R Further information [email protected] •Phone(08)97810125 Travis Cattlin•Senior Hydrogeologist Department ofWater •Busseltonoffice iver healthassessment Winter flow Environmental Protection and Biodiversity inth ) seek refuge in the e lowercatchmentof

t he BlackwoodRiver year round. rivers how and it keeps water flowing full or pools determined groundwater how much flows into the downstreamand of points, these we have By measuring summer flow volumes upstream before flowing out back again at different points. underground time little very riversthe spends outcrop. tells This that us water the that supports aquifers to surface, the or come Leederville downstream of where Yarragadee the and rain groundwater and are samples present only found tracers in thedetermined chemical the in particular,In studying Blackwood the we drying climate. drying of resource the in face the sustainability ofthe a we manage and to need knowledge understand of research gives south-west,the the sort us this rely rivers the tourists on aquatic and of species soBecause many businesses, communities, overoutflow years. coming the likely the inpredict groundwater-to-river changes rainfall groundwater and use. us helps This groundwater systems to are reduced responding an excellent indicator of how region’s the riversStudying the of south-west the provides Why are thesediscoveriesimportant? Summer flow

Western Australia Western of Government © www.water.wa.gov.au Margaret River (mg/L) salinity Blackwood River (mg/L) salinity

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