5 things you didn’t know about Centennial Park’s ponds

The 11 ponds in Centennial Park are some of the most popular features that visitors enjoy, but beneath the surface of these placid waterways are some interesting facts you may not be aware of!

Centennial Parklands has eleven ornamental ponds, covering an area of around 26 hectares. They provide important habitat for water birds and aquatic life and form the upper catchment of the Botany Wetlands, the largest freshwater wetland system in inner-metropolitan Sydney.

Here are five fascinating facts about our ponds that you may find interesting…

The ponds were originally dams

In the 1830s Lachlan Swamp, in present day Centennial Park, was used as a key water source for Sydney. As part of the process of getting water from Lachlan Swamp to the Sydney town a bore (Busbys Bore) was constructed.

As part of this process of ensuring the water source was reliable, a series of dams were built, however large-scale flooding in 1874 destroyed these dams, requiring seven new dams to be constructed.

When Centennial Park was established in 1888 these seven dams were remodelled into many of the ornamental ponds you see today.

The ponds are fed from outside and underneath

The ponds in Centennial Park play an important role in flood mitigation for the wider catchment area. They act as a detention basin, capturing stormwater runoff from surrounding suburbs such as Paddington, Woollahra, Bondi, Waverley and Randwick.

The diagram below shows where stormwater enters the Parklands’ waterways, and then moves (in a downhill manner) through the pond system before exiting the Parklands on Alison Road which will eventually end up in Botany Bay.

One pond has a natural spring beneath

Lily Pond in Centennial Park is more than just a pretty backdrop. Unlike the other ponds in the Parklands that are fed by stormwater, Lily Pond is actually fed by a natural, underground spring in Lachlan Swamp.

The water in this pond is usually clearer than other ponds in the Parklands for two reasons:

• iron pyrites in the soil oxidise, releasing sulfur dioxide and causing the spring water to be slightly acidic – and therefore clearer;
• the water in the pond is filtered up to the surface through sand – contributing to its clearer appearance.

They're wide but shallow

It is often the case that park visitors may drop personal items in the pond, from glasses to cameras, and even bikes. Our Rangers are often required to retrieve these items, but many people don’t realise that specialised diving equipment isn’t necessary. The ponds may be big and wide, but they aren’t very deep.

In the style of 19th century urban park design, the ponds in Centennial Parklands are quite shallow – mostly less than 2 metres deep at their lowest points. Towards the shoreline, the ponds are often ankle to waist deep at most.

This shallowness of pond design is a European tradition, but does bring its challenges in an Australian climate. A very large, but shallow, surface area of water can suffer from evaporation loss in hot weather.

Since the ponds are stormwater fed, in periods of prolonged dry weather or drought the ponds can rapidly become depleted.

This means that the health of our ponds are in our hands, so we have several strategies in place to reduce the onflow and impact of stormwater pollutants in the ponds:

• use of ‘Gross Pollutant Traps’ at key stormwater entry points to capture larger waste items;

• aquatic plantings which provide stability for banks and improve the quality of the water by filtering out some dissolved toxic pollutants such as phosphorus;

• the addition of new islands and underwater berns to prevent water from becoming stagnant;

• regular water analysis and occasionally, use of an aerobic bacterial treatment method that helps to reduce built up organic matter, nutrients and various other organic compounds

The ponds are home to some amazing residents

Centennial Park is a haven for wildlife, but many of our animal residents live below the surface like the long-fin eel.

Help us protect our ponds

If you are in any doubt about the impact of waste and pollution in Centennial Parklands’ ponds, then take a look how they used to look in the early 1980s! Thankfully, these days they are in much better shape, but we need everyone to ensure we protect our ponds for years to come.

Visitors to the Parklands and residents in surrounding suburbs can help keep our ponds clear of pollution. What goes into the drain in the street, or gets left on the ground in the Parklands, finds its way into the stormwater system, and eventually into waterways like the ponds in Centennial Park.

Polluted stormwater is bad for biodiversity because it often contains materials that are harmful to the living things in that ecosystem.

You can help keep our waterways clean and healthy by:

• sweeping your gutters and driveways with a broom rather than hosing rubbish down the drain;

• washing your car on the grass – putting soapy water down the drain encourages the growth of algae and can sometimes poison our aquatic wildlife;

• pick up your dog’s poo – the nutrients in the faeces can encourage algal blooms

• always place waste in a bin, never pile rubbish next to a bin or leave rubbish on the ground in the Parklands.

• Thanks for your support!