Lake Hawdon North Regulator

As part of the Healthy Coorong, Healthy Basin initiative, Tonkin was engaged to support the Department for Environment and Water (DEW), to undertake large-scale wetland restoration at Lake Hawdon North (LHN), in South Australia's Limestone Coast region. 

Tonkin was engaged to provide the detailed design of the restoration project, after completing concept designs for the Lake Hawdon North structure in 2020.

LHN is a seasonally inundated wetland and forms one of the largest wetland systems in the region.  To support the conservation of endangered and vulnerable shorebird species, on-ground works were implemented to improve the sites ecological character, increasing availability and quality of habitats for migratory and non-migratory shorebirds, resulting in approximately 1,7763 ha of suitable habitat being available during critical times.   

The project addressed ongoing impacts of a major agricultural drain (Drain L) built in 1915 that severely compromised LHN’s hydrology, resulting in the site becoming too dry in the summer, reducing habitat and food resources for shorebirds. 

Central to improvements was the construction of a regulator on Drain L, which provided a unique management opportunity for variable habitat across the region and increasing resilience in the system. The regulator was designed to manage water levels to recreate a more natural hydrological regime and maintain shallow inundation of the lakebed through late spring and summer, increasing optimal habitat for key shorebird species. 

Works included installation of an adjoining rock-ramp fishway to ensure safe fish passage, access tracks, fencing and habitat modification to restore the site to an open mudflat environment.

Our skilled team used innovative construction methods, paired with methodologies adapted to minimise environmental impacts and water manipulation techniques, to ensure the highest-quality sustainability site management. 

The regulator has enabled improved site management, allowing LHN to meet needs of key environmental habitats, supporting both environmental and agricultural production values that are affected by water resource manipulation.

The project’s most impactful sustainability benefit is the contribution to water use efficiency by allowing precise control of wetland inundation cycles to support ecological resilience under changing climate conditions. 

By better managing available water for targeted inundation at strategic times, nutrient absorption and groundwater recharge are increased and freshwater discharge to the ocean is reduced, therefore resulting in regionally sustainable water use and optimal environmental benefits.  

The benefits of the Lake Hawdon North (LHN) Regulator are widespread across the community! 

Declines in the diversity and abundance of waterbirds in the Coorong have been linked to declines in the quality and availability of waterbird foraging habitat. By enabling the increase in shorebird habitat during the crucial shorebird season, the LHN project is actively mitigating this regional problem by providing beneficial refuge habitat for species that would otherwise utilise the Coorong South Lagoon.

LHN currently supports 40 species of wetland dependent birds, including 8 migratory shorebird species and, when combined with adjoining Lake Hawdon South, is one of the largest wetland systems in the region. Through operation of the regulator, water levels reached the target operating level and demonstrated its value to shorebird and waterbird populations by harbouring over 20 species of waterbirds, some in flocks exceeding 30,000. 

From a community perspective, the restoration and preservation of wetlands is of cultural, spiritual, social and economic significance to the First Nations of the South East as the restoration of LHN aligns with their aspirations to reconnect and Care for Country using their Walking Seasons process. The project worked with the South East Aboriginal Focus Group throughout the project to ensure cultural knowledge, values and interests informed and shaped project outcomes.

The $11.69 million project, jointly funded by the Australian and South Australian governments, delivered a new water regulator to manage water flows across Lake Hawdon North wetland system, creating the right condition for native vegetation and wildlife to flourish. 

The project is a perfect example of how well-planned and designed engineering solutions deliver superior environmental, biodiversity and sustainability outcomes.

Sarah Murphy, from the Department for Environment and Water said:

The Lake Hawdon North Regulator project won the Excellence in Environment and Sustainability award at the 2025 IPWEA SA Excellence Awards.