$3m Adelaide City Council plan to use recycled stormwater to save Rymill Lake

It regularly fills with algae, becoming an eyesore. Now a $3m plan has been hatched to save a popular lake in the heart of the city.

Stormwater will be used to replenish Rymill Lake under a proposed $3m scheme to save it from algal outbreaks.

The lake regularly is closed during summer, when high evaporation rates and duckweed render it unsuitable for water activities like rowing boats.

The Adelaide Park Lands Authority has been briefed on a proposal to use small water basins upstream to feed stormwater into the lake through Botanic Creek.

The creek was diverted around the lake in the 1950s through a concrete drain.

Under the new scheme, stormwater will be trapped in nearby parks and released into Botanic Creek, which will be rehabilitated.

Recycled water from the Glenelg Wastewater Treatment Plant is currently used to top up the lake.

Rymill Lake is cleaned during an outbreak of duck weed. Picture Sarah Reed

The future of the lake has been under examination as part of a draft masterplan.

Two options previously have been considered – maintaining it as an ornamental structure or converting it into wetlands.

A report presented to APLA said the lake’s future had been under scrutiny since 2007, when an audit found it was leaking because of “significant structural issues” with its walls and base.

“A temporary liner was installed but due to statewide water restrictions at the time, the lake was unable to be refilled with mains (potable) water,” it said.

“In response to the water restrictions, a connection was made to the lake to recycled wastewater supplied by the Glenelg to Adelaide pipeline.

“These temporary solutions addressed the high cost of water to maintain lake levels and

allowed time to consider the longer-term vision and design for the renewal of the lake.”

Adelaide City Council is confidentially assessing a proposal to reopen the Rymill Park kiosk.,

The report said the lake was a “shallow water body with a large surface area”, creating high evaporation during summer.

“Combined with poor water circulation and high nutrient loading from recycled wastewater used to fill the lake, it often has poor water quality leading to outbreaks of algal blooms in the summer months which exceed public health thresholds, leading to it being closed,” it said.

“This impacts on the kiosk operators, festivals and events held in the park and visitors.”

Rymill Lake could be filled with stormwater under a $3m scheme. Picture: Matt Loxton

The report said attempts to fix the lake had been delayed by the construction of the O-Bahn tunnel and development of a masterplan.

This had led to the proposal to divert stormwater into the lake, rather than continue using the water from Glenelg.

The creation of a new catchment zone in nearby parks and rehabilitation of Botanic Creek will be presented to Adelaide City Council for consideration early next year.

The council has been confidentially considering a proposal from a private operator to take over the kiosk at Rymill Park.