Perth Laboratory – Public Seminar Series 2009

Groundwater in a marginally saline water supply catchment

Robin Smith
Salinity and Water Resources Recovery Branch
Western Australian Department of Water

Thursday 11 June 2009 at 3.30pm, CSIRO Auditorium

Abstract

The Helena (River) Water Resource Recovery Catchment above the Mundaring Weir is 97% forested. It experiences a low rate of runoff which is increasing in salinity. Water salinity first began rising soon after CY O’Connor completed the pipeline to Kalgoorlie. The Salinity Situation Statement describes catchment characteristics, the effects of past and current practices and predicts outcomes of various management options. For the Helena catchment:

• The flow-weighted reservoir inflow salinity (1990–2002) is 510 mg/L with a range 305–719 mg/L.
• Only 3% of the catchment is cleared, but about half is in the north where discharge from palaeochannel sediments carries most of the salt.
• The Helena River contributes 63% of the reservoir’s salt load and only 30% of the inflow, including substantial discharge from recently recognised palaeochannel sediments.
• Reduction of inflow salinity to potable levels (below 500 mg/L) would follow

1. replacement of up to half of the current annual pasture with commercial trees or deep-rooted perennial pastures,
2. pumping to reduce groundwater seepage,
3. diverting saline flow out of the Helena River, or
4. rainfall remaining below average.

About the speaker

Robin Smith is the supervising hydrogeologist in the Salinity and Water Resource Recovery Branch of the Department of Water. He obtained his science degree in Geology from the University of Adelaide and Earth Sciences Honours from Flinders University of South Australia, majoring in hydrogeology.

Since joining the Geological Survey of Western Australia in 1979, he has compiled 1:250 000 geological and hydrogeological maps, assessed the groundwater resources of Rottnest Island, supervised deep exploratory drilling of the Perth and Canning Basins, contributed to the Perth Urban Water Balance Study, and compiled hydrogeological bibliographies for Western Australia. He has recently completed the Salinity Situation Statement for the team investigating the Helena River catchment and co-authored several palaeochannel hydrogeology papers.

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