The Willunga Basin Pipeline - a triple bottom line role model

The Willunga Basin Pipeline in South Australia is a large reclaimed water scheme which is owned and operated by its water users. Despite being funded without government assistance, it continues to expand, providing a catalyst for economic growth, replacing stressed groundwater and reducing nutrient discharge to the sea.

The first water users formed a joint venture and company (The Willunga Basin Water Company - WBWC) to build Stage 1 of the pipeline so that they could pursue their core business of irrigated horticulture (mostly viticulture). Over the last five years, the WBWC has expanded the scheme five times to almost double in size so that their neighbours can access water as well.

The primary water source is the Christies Beach Wastewater Treatment Plant (CBWWTP). It is about 10 km north of the Willunga Basin, and is one of four metropolitan treatment works. The annual treated volume is around 10,000 ML. There is sufficient 'waste' water flowing to sea from CBWWTP to replace the annual abstraction of groundwater for irrigation in the Willunga Basin. Vic Zerella, a local grower and winemaker, and John Gransbury of Hydro-Plan worked together to obtain permission from the government to use the CBWWTP water. Hydro-Plan developed the engineering concepts and a budget so that Vic could approach enough landholders and water users who were willing to form a group that would build the pipeline.

As mentioned, the water users formed a joint venture and toll company to build and operate the pipeline. Participants contributed funds towards construction in proportion to the maximum flow rate they would take from the pipeline. Although the water users funded 100% of the pipeline, they only allocated themselves 25% of the water it can deliver. This provided for third-party access requirements and allows for expansion to other areas in the Willunga Basin, without duplicating the pipeline.

An irrigation management plan (IMP) is a key part of the approval process for reclaimed water use in South Australia. The IMP is based on comprehensive guidelines, submitted to the EPA and updated annually. The objective of the IMP is to describe the sustainable management of the reclaimed water irrigation scheme. It takes into account the physical features of the sites to be irrigated, soil characteristics, impact on surface and groundwaters, and public health.

Hydro-Plan designed new on-farm irrigation systems, reviewed existing systems, and designed headworks. Soil and crop management reports were commissioned and seminars were conducted.

Under the water supply agreement, individual users take responsibility for the interaction of their on-farm irrigations system and the environment. Users agree to use drip irrigation and not spray irrigation.

Users schedule their own water deliveries by turning on their taps. There is no 'water ordering' system. Each outlet has a flowmeter and water usage is logged continuously so that stiff penalties can be applied for 'flow rorting'.

Dams are topped up automatically at night or when required to pre-determined target levels which make use of off-peak pumping tariffs.

The water quality from CBWWTP is defined as Class B under the South Australian Reclaimed Water Guidelines. E.coli levels and BOD would consistently meet Class A standard but suspended solids do not - tertiary filtration would be required.

The Willunga Basin Pipeline is a good example of how Australians work together to solve water resource problems. This scheme is beneficial to the company, the community and the environment.