Let's pump, says Elizabeth Macarthur Agricultural Institute manager, Greg Wall, waiting for recycled effluent water to irrigate the Institute's improved pastures from this new 63 megalitre storage dam, and help both the Nepean River and the Camden sewage treatment plant.

Diverting tertiary treated effluent away from the Nepean River onto agricultural land at Camden will provide multiple benefits.

One of the main irrigators on the Nepean, Elizabeth Macarthur Agricultural Institute (EMAI) will shortly be able to substitute treated effluent for most of the water it extracts from the river.

West Camden sewage treatment plant now discharges the treated effluent to the river but soon a new pipeline will divert a substantial amount to fill a newly constructed 63 megalitre storage dam nearby at EMAI.

'We’ll be able to draw up to four million litres of high quality treated wastewater a day from the dam, instead of fresh water from the river,' said the lnstitute man-ager, Greg Wall.

The sewage treatment plant is being upgraded to cope with booming population increases in the district.

It currently treats nine million litres (nine megalitres or ML) perday; once upgraded the capacity will exist to treat 23 ML per day of flow to produce high quality treated effluent. Immediately, approximately 11 ML will be treated, with the full capacity not expected to be reached until 2020.

The pipeline will have a capacity of 10 ML per day, so in future, other landholders in the area may also tap the supply.

Mr Wall said EMAI will use the treated water it receives to irrigate improved pastures associated with grazing and fodder production at the Institute’s dairies.

'The dam will provide a reliable alternative water supply, up to 730 megalitres a year, and guarantee irrigation water to improve the farm’s long term viability.

'Delivery of recycled water provides an opportunity for EMAI, as a major irrigator, to further improve operational and irrigation practices.'

Reduced effluent discharges into the Nepean will help to improve the health of the river’s ecosystem.

'The diversion system will be particularly useful during drought,when the slow flushing effect of low flows makes the discharge of treated effluent least desirable,' said Raju Mangalam, from Sydney Water.

'Reduced extraction of fresh water for irrigation from the river will contribute to environmental flows.'

EMAI submitted an irrigation drainage management plan as a prerequisite for the project, to ensure the water is best used, so problems like salinity do not occur later.

Sydney Water is about to construct the pipeline to EMAI and expects to start pumping towards the end of the year.

'The distance between paddocks on the property means recycled water will take care of 70 per cent of irrigation in the short term, the balance to be extracted from the river,' Mr Wall said.

The Soil Conservation Service, a division of the Department of Lands, constructed the dam, in a joint venture with the NSW Department of Primary Industries and Sydney Water.

To ensure no natural runoff can enter the dam, exceed storage capacity and create the possibility of effluent overflowing, the damwas built in 'turkey’s nest' style.

The constructors had to move 27,000 cubic metres of soil and installed a liner in the wall as an added precaution against leakage, recommended by the soil test report.

Contact: Greg Wall, (02) 4640 6333 or greg.wall@dpi.nsw.gov.au

This story appears in Agriculture Today.