City of Onkaparinga, Australia

Concern for the future water supply of the City of Onkaparinga generated a localized integrated water resource management strategy, “Waterproofing the South.” This effort developed eight projects with a combined capacity to meet the plan’s goals. Through the creation of a water infrastructure plan to capture and treat stormwater and wastewater for reuse, the strain on traditional water sources is alleviated. This has allowed the community to become self-sufficient and water secure – able to ensure a reliable supply of water for future generations.

Project Summary

The City of Onkaparinga is a Local Government Area (LGA) located on the southern fringe of AdelaideSouth Australia. It is the largest LGA in South Australia, with an estimated population of 164,800 people in both urban and rural communities. Geographically, the area is expansive, encompassing an area of 518.3 km² (approximately 200 square miles). Currently, a continual flow of water year round is retained by pumping water from the Murray River. The effects and limitations of this system, combined with climate change, have created concern for the city’s future water supply. “Waterproofing the South” is a localized integrated water resource management strategy for the City of Onkaparinga. It promotes sustainable water use by providing alternative water sources to replace the use of traditional sources, such as piping river water and groundwater. The strategy also creates a secure source of water for the community through the development of the water reuse infrastructure. The focus of this strategy is the capture and reuse of wastewater and stormwater. The topography of the area offers opportunities for capturing stormwater by channeling flows into nine different catchment areas. Improvements to the wastewater treatment plant allow water to be supplied for agricultural and urban uses, reducing the nutrient load to the Gulf and the demand on potable water supply. Eight projects were selected and developed in conjunction with the plan to increase the amount of urban and rural water reuse, increase network storage capacities, create water saving, and to understand the suitability of treated wastewater to supplement water from the Onkaparinga River.

Plan Highlights

Environment

Several of the initial projects explicitly address the threats to the environment. These include addressing flooding risk, protecting water quality, and protecting and enhancing water dependent ecosystems.

  • The Morrow Road sedimentation ponds treat stormwater in the lower reaches of Christie Creek prior to it entering the marine environment. This process removes at least fifty percent of suspended solids, which could potentially resettle on reefs leading to the loss of sea grass.
  • The Wilfred Taylor Water Reserve has been created, with the capacity to harvest 850ML (approximately 225 million gallons) of stormwater for reuse, which addresses flooding risks and improving water quality.

Infrastructure

The key goal of Stage 1 of Waterproofing the South is to create infrastructure which will allow for wastewater to be collected and reused as many times as possible to reduce the nutrient load to the Gulf and reduce the demand on the potable water supply. Wastewater that once flowed out to sea is now returned to the city for irrigation of parks and reserves, and used as an important supply of water to industry and wineries.

  • The Christies Beach Wastewater Treatment Plant quality upgrade will provide reclaimed water for agricultural and urban use. The increase in reuse will improve the quality of the discharge to the marine environment and reduce demand on potable supply.
  • The city has developed a 17km (10.6 mile) distribution scheme to distribute collected stormwater for irrigation.

Process

This initiative was achieved through support from the state and federal government. Continued funding was then secured by demonstrating measured success of the initial pilot projects.

  • The Australian Government provided $34.5 million (AUD) for the project. The City of Onkaparinga Council, SA Water Corporation, Adelaide and Mount Lofty Ranges NRM Board, Willunga Basin Water Company and Flinders University also contributed to the project to provide a total investment of approximately $122 million (AUD).
  • This project has been developed as a partnership between SA Water and Willunga Basin Water Co.

Lessons Learned

The integrated approach of Waterproofing the South allows multiple projects to work together to maximize the potential outcomes of the plan. By looking at the various water issues and opportunities of the region comprehensively, the city was able to coordinate efforts to reach their goals of water capture, reuse and quality improvement.

The success of the initial eight projects (now classified as Stage 1) has led to a second phase of the initiative, which will build upon the previous phase and is currently being developed. The Council has received approximately $15M (AUD) in funding from the Australian Government through the Water for the Future initiative and $7.5M (AUD) from the State Government to support the delivery of the $30M (AUD) Water Proofing the South Stage 2 initiative. Developing a comprehensive strategy for the city was imperative, and focusing pilot projects to highlight the potential success of the plan is an effective strategy for garnering political support and financing.