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Water arrives in Annandale as Rainfall, Runoff (from neighbouring suburbs) and through the Water Supply.
Water flows out of Annandale via the Sewage system to a treatment plant. Rain water drains into the harbour via storm water drains and Johnston and Whites creeks.
Federal Park Wetlands, December 2008
As an inner city suburb - most of Annandale is covered by non-porous surfaces - bitumen roads, building and paving. This means that instead of being absorbed, into the soil, and made available to plants, in gardens, it runs off into the Johnston Creek and Whites Creek.
Along its way to the creeks, the water collects surface pollutants from the pavements, roads, parks and gardens. The Federal Park and Whites Creek wetlands have been constructed to filter out some of the nutrients and debris, before the water enters the harbour.
Pollutants that are picked up along the way often include:- Water Quality (LMC)
- Oils and grease from cars
- Litter left on the ground
- Sediments from construction sites
- Leaf litter
- Chemicals including pesticides, fertilizers and cleaning products
- Dog droppings
Whites Creek Aqueduct by Joel Tarling.
The Whites Creek Johnstons Creek Sewer Aqueduct built in 1895 was the first reinforced concrete structure to be built in Australia - A brief History of Concrete in Australia (PDF)In dry weather, overflows of sewage can occur for many reasons. For instance, when there is a blockage in a sewerage pipe caused by tree roots or other material, or if a pump fails at a pumping station. At treatment plants, bypasses may result from a power failure.
In wet weather, stormwater flows into the sewerage system and may exceed the system's capacity and result in overflows from our pipe network and/or the diversion (bypassing) of one or more process units at the treatment plant. These events are recognised within the Environment Protection Licences set by Department of Environment and Conservation (NSW). - Sewage overflows (Sydney Water)
Some Rain and Runnoff may be absorbed into the ground, this is augmented by people watering their gardens. Water that has seeped into the ground is then transpired by trees and other plants. Some of the water is filtered through the soil and eventually ends up in Whites Creek, Johnstons Creek, and the Harbour. Water also evaporates from hard and soft surfaces.
Just as drinking water can be filtered to remove impurities, the soil particles filters rainwater percolating through soil on its way to surface waters and to groundwater aquifers - permeable pavement(www.toolbase.org )
Without Soft (porous/permeable) surfaces, water cannot enter the ground. This means the water level drops and it takes a lot of hand watering to improve the water level. Clay soils are common in Annandale. When clay dries out and shrinks, it can cause cracks in buildings. Engineering solutions include, rehydrating the soil.
Cracking in buildings is common in NSW and particularly in the Strathfield Municipality. Most of Strathfield Municipality is built upon reactive clay soil. During periods of drought, clay soil 'shrinks' when it dries out and buildings supported by these soil types tend to settle unevenly when the shrinkage occurs, leading to cracking in brickwork particularly around window and door openings. However, after periods of rain, dry clay soil can 'swell'. Swelling of soil can also cause cracking and lifting or heaving of buildings. The 'shrink' and 'swell' cycles can also cause cracks to open and close without significant extra damage. - Strathfield Council
In cities and suburban areas, millions of square feet of concrete, asphalt, roofs, and other impermeable surfaces create enormous quantities of runoff which can overwhelm natural drainages, over saturate the areas where water does collect, and divert water away from groundwater reservoirs. - Sustainability Indicators - Permeable Surfaces (City of Minneapolis)
Collins and Trafalgar Streets intersection after heavy rain on 14th June 2007.
The plinth will be a low (190mm) rectangular shaped platform encompassing the space originally planted with turf. The new paving on the plinth will be permeable to allow air and moisture to the trees, whilst creating a durable, flexible and low maintenance platform which will ensure the future health of the trees while allowing easy access through the central courtyard. The paving will be a grey "ecolock" type paving, which was used for the forecourt of the Homebush Olympic stadium. - Macquarie University Central Courtyard Upgrade Project
[Leichhardt Municipal] Council is committed to improving stormwater management in the Municipality to keep our waterways clean and maintain a healthy environment. The objective of Council's Stormwater Management Strategy is to ensure that stormwater is managed in a manner that conserves and enhances the ecological, environmental, social and economic values within the storm water catchments. -Drainage Code (LMC)