Metropolitan beaches in Adelaide's west have suffered the worst pollution residents can remember after the city's lake was repeatedly flushed throughout summer to reduce blue-green algae.

Key points: Five metropolitan beach alerts issued for pollution

Five metropolitan beach alerts issued for pollution Swimmers warned from the water by surf lifesavers

Swimmers warned from the water by surf lifesavers A clean Torrens Lake is a priority for festival season

A clean Torrens Lake is a priority for festival season Stormwater retention at the source is "a solution for pollution"

No fewer than five beach pollution alerts were issued over summer, and swimmers were warned off as freshwater flows from the Torrens outlet at West Beach resulted in a brown strip of water on the shore.

It stretched two kilometres to Henley Beach and a further two kilometres to Grange, and was sometimes accompanied by sickly looking algal spores.

"It was stinky. It was brown. It was disgusting," Grange resident Angela said.

"I was warned not to swim in it by the surf lifesavers.

"I initially thought it was just bad weather and it was all seaweed, but the closer I got to the water, I thought, no, this doesn't smell right. It was the worst year [for pollution] in 30 years."

The Environmental Protection Authority issues beach alerts when water quality is poor and poses a potential health risk to swimmers.

It issued a warning at West Beach next to the outlet on December 7 and 8, which included Henley Beach.

On February 2 swimmers were warned again from the water at Henley Beach, as well as further south at Glenelg, Hallett Cove, Christies Beach and Moana.

On February 22 and March 10 beach alerts were issued for all of Adelaide's metropolitan beaches.

Regular West Beach visitor Pavlos Kounavelis said it was regularly smelly in the area and his father fell sick after swimming on one occasion.

"He was a little bit elderly at the time and he plunged into the water," he said.

"My mum said 'don't get in the water'. In the next two weeks he had ear infections and all sorts of things."

A strip of brown water marks pollution at the foreshore between West and Henley beaches west of the CBD. ( ABC News: Chris Nilsen )

Algae 'flushed from sight' for the festival season

Summer's pollution began during November and December when several hot spells and a record-breaking heatwave resulted in toxic blue green algae outbreaks in Torrens Lake, an engineered lake on the River Torrens in the city's CBD.

The $8.4 million Henley Square project opened over summer. ( ABC News: Malcolm Sutton )

Freshwater was released from upstream into the lake to break-up the algae, twice in December, and once during January and February, and the water was flushed downstream.

In January a small trial took place to add hydrogen peroxide to the water - used in bleach and for whitening teeth - in an effort to reduce algae, but rainfall limited results.

Kym Good from the Natural Resources Adelaide and Mount Lofty Ranges Board (NRAMLR) said with public events centred around the lake, including the Tour Down Under, cricket at Adelaide Oval and the approaching festival season, "the economic benefit of a healthy lake could not be overstated".

"It's vital that visitors enjoy a genuinely positive experience and the lake being open and available for recreational use contributes to that," he said.

But downstream near its discharge point into the Gulf St Vincent, the City of Charles Sturt had just opened its refurbished $8.4 million Henley Square.

Asset Management Services general manager Jane Cornish said the council received about a handful of calls from concerned residents but it did not mean more people were unconcerned.

One worker in the area told the ABC there was an expectation that Henley Beach just "sucked it up".

Ms Cornish said the council had talked with the State Government about the timing of water releases, and had recently been invited onto a "working party" involved in decision making.

"We don't want the water hit on the weekend, for example, so it might arrive on the Monday, but hopefully by the Friday it might have petered out and disappeared."

Ms Cornish said Charles Sturt Council had been working with the SA Government to divert water from the Torrens into wetlands at St Clair and at Old Port Road, and this year had taken about 500 megalitres - the equivalent of about 250 Olympic sized swimming pools.

She said a lot of councils along the River Torrens were working with the NRM Board to install gross pollutant traps and create wetlands to pick up some of the pollutants going down the river before they discharge.

NRAMLR communications manager Chris Booth said the board's trash racks and gross pollutant traps had prevented 3,700 tonnes of sediment and pollution entering the sea via the Torrens Outlet and the Patawalonga catchment (Glenelg) in 2014-15.

Algae flows downstream towards West Beach while upstream Torrens Lake retains a healthy appearance. ( ABC News: Chris Nilsen )

Stormwater 'the biggest contributor' to pollution

Mr Booth said the bulk of water that entered the sea from stormwater resulted from rainfall in the river's catchment from the hills to the coast.

He admitted flushed water from Torrens Lake was discharged at West Beach but said the quality was "significantly better than a normal stormwater flow".

"Monitoring is undertaken during controlled releases at the river outlet and in the sea for turbidity, a measure of how dirty the water is, and Enterococci, a measure of the presence of bacteria," Mr Booth said.

"The risk to beach swimmers is low. Cautionary advice is given at all times for people to avoid swimming or wading in discoloured water."

Mr Kounavelis said there were was a sign up at West Beach warning people not to swim but it usually got "mown down, by somebody, who takes it home or something".

"The next day everybody's in there plunging around. It's nuts, isn't it?"

Water flows out to sea from the outlet at West Beach. ( ABC News: Chris Nilsen )

Gulf St Vincent 'susceptible to pollution'

Former CSIRO head Professor Graham Harris from the University of Wollongong, New South Wales, was the chairman of the 2013 Adelaide Coastal Water Quality Improvement Plan.

Dirty bubbles on the sand on Adelaide's west beaches. ( ABC News: Malcolm Sutton )

He said Adelaide's coastal waters were susceptible to pollution caused by urban stormwater because they were historically nutrient poor.

Prior to white development, run-off accumulated in freshwater lagoons behind the sand dunes, which prevented nutrients from entering the Gulf St Vincent.

"The natural Australian environment is pretty poor in nitrogen," Professor Harris said.

"Even if it rained the nutrient run-off would have been pretty low.

"Over the years, development happens, populations rise, sewage loads increase and nutrient loads tend to go up.

"And people don't like flooding from stormwater, so they cut the stormwater branch through the beaches and stormwater goes out to sea."

Professor of Water Resources at Victoria's Swinburne University Peter Coombes is an author of revised guidelines for the Australian Rainfall and Run-off project, a national guideline on flood estimates used to assess infrastructure requirements.

He said pollution at Adelaide's western beaches had been a "recurring problem" for years due to 19th century engineering designed to remove stormwater from urban areas as quickly as possible.

Sorry, this video has expired Algae appears in Torrens Lake despite scheduled flushing

He said ongoing development and construction had increased hard surfaces in urban areas, and increased the load on water courses, "and that's clearly what has happened at Henley Beach".

Professor Coombes said it was a common misconception that large scale infrastructure changes were required when, in fact, a "soft" and more "holistic" approach to stormwater management would make a difference.

This included capturing more rainwater at the source upstream and using it for requirements other than just drinking water.

It also involved capturing stormwater at parks and gardens, storing it in local aquifers, and treating and sending the water back to the catchment it came from.

"Adelaide is the driest place that just happens to have a lot of stormwater running off of it," Professor Coombes said.

"It's such a travesty of missed opportunities."

He added that when authorities said a mitigation project did not stack up financially, people needed to look more closely at the details because often a project's benefits were not included in its cost assessment.