Anglesea Futures

Acid Events in the Anglesea River Catchment

The Anglesea River experiences occasional acidic or low pH water quality events due to natural sources of acid in the catchment. These events are natural occurrences and are often the cause of fish deaths in the Anglesea River.

What are acid events and when do they occur?Acid events occur when soils that contain sulfuric acid, or have the potential to form sulfuric acid, are exposed to oxygen in dry conditions. When the dry sulfuric materials are exposed to water from soaking rainfall, sulfuric acid is released.

Surface water runoff collects and transports the acid from the upper catchment into Salt Creek and Marshy Creek, the main tributaries to the Anglesea River. When the acidic flow from Salt and Marshy Creeks enters the Anglesea River estuary it lowers the pH of the water in the estuary resulting in an acid event.

Rainfall intensity and timing are the key determinants of whether or not an acid event occurs. An acid event is most likely to occur when a long dry spell is broken by soaking rain.

What are the impacts of acid events?Acid events can impact on estuarine health, reduce recreation opportunities and affect public enjoyment

of the river and its environs. Historically acid events have caused fish deaths in the Anglesea River.

Is the river safe to swim in during an acid event?To protect public health when the Anglesea River is acidic, Surf Coast Shire Council, Department of Health and Human Services and Environment Protection Authority (EPA) Victoria advise the public not to eat dead or dying fish and not to swim in the river as this may cause eye or skin irritation.

The National Health and Medical Research Council guidelines recommend that waters used for primary recreation, such as swimming should be in the pH range of 6.5 – 8.5.

Public health warning signs are installed by Surf Coast Shire Council when the river becomes too acidic (< pH 6.5) and are removed when the water quality readings return to the national standards acceptable for swimming (> pH 6.5).

Will fish return to the river estuary?Fish do return to the river as the pH returns to neutral. A survey undertaken by Arthur Rylah Institute after the 2010/11 acid event in the Anglesea River identified 17 different species – more species and individuals than on previous occasions.

What is being done about it?The Anglesea River recovers naturally from acid events as the catchment upstream dries out and the pH returns to neutral.

www.delwp.vic.gov.au

Anglesea Futures

Surf Coast Shire Council and Corangamite CMA will continue to monitor water quality so the community can be given as much notice as possible of an acid event occurring in the Anglesea River estuary. Monitoring will also be undertaken to track the recovery of water quality and pH in the system.

An expert panel convened in 2014 considered various options for managing acid events in the Anglesea River. Several options were not considered as suitable for further consideration because of risks and/or costs were seen to outweigh the benefits, these options included, deep artificial openings, removal of the remnant rock wall, construction of storages/dams in the catchment and the construction of fish refuges.

Options for the rehabilitation of the mine site are currently being investigated, which may change how water in the upper catchment flows to the lower catchment. None of these options are expected to stop acidic or low pH water quality events, caused by natural sources of acid in the catchment, occurring in the short or long term.

The Corangamite Catchment Authority, Surf Coast Shire Council and the Department of Environment, Land, Water and Planning support natural recovery of the Anglesea River from acid events.

Who do I call to report fish deaths?Public reports of fish deaths can be made to EPA’s Pollution Hotline on 1300 372 842 (1300 EPA VIC). If possible, provide the following information:

location and time of the incident

whether fish are dead or merely affected

approximate number of affected/dead fish and whether they are fresh or decomposing

whether other fauna are affected, and

condition of the waterway (flow, colour, odour etc.).

EPA’s Waterway Incident (Fish Death) Response Guideline (publication 1068) lays out the roles and responsibilities of water management and environment agencies for responding to fish deaths.

Surfing lessons on the Anglesea foreshore. Image courtesy: Go Ride a Wave.

What else can I do in Anglesea during an acid event?There are still lots of things for residents and visitors to see and do in Anglesea during an acid event. You can explore any number of playgrounds, walk nature trails, ride along some of the best coastline and there are many cafes, tourism and retail traders that are open for business.

Anglesea has some of the finest beaches on the Surf Coast. The main beach at Anglesea and the Point Roadknight beach offer safe swimming options. Visit www.angleseaadventure.com.au for ideas on things to do in Anglesea.

Anglesea Futures

Snorkelling in rock pools. Image courtesy: Eco-Logic Education & Environment Services.