Stormwater Quantity
In recent times, attention is turning towards not only treatment but also re-use of stormwater.
It is estimated around 16,870 megalitres of stormwater runoff is discharged to bays and harbours each year from rain which falls in the City Local Government Area (LGA). This is approximately half of the total water consumed in the LGA each year.
Stormwater discharge (storm event) in the City of Sydney LGA
Total runoff volumes, based on average recurrence interval (ARI) rainfall events, are shown in the figure above. These have been calculated using imperviousness values for each land use zone.
Stormwater discharge (catchment) in the City of Sydney LGA
Total annual runoff volumes are shown for each catchment in the figure above. The results are based on 1,100mm of rainfall and only include catchment areas within the City of Sydney LGA.
It is interesting to note there is as much water in one hour in a 1:100 year ARI storm event across the City LGA as from many of the smaller catchments in an average year.
In 2003 stormwater modeling was conducted in the Blackwattle Bay catchment. As summarised below, approximately 72% of rain that falls in the catchment each year is discharged as runoff.
Water
cycle in the Blackwattle Bay catchment
Source: Ecological Engineering Pty Ltd
Last Updated: Monday 27 April, 2009
