Sydney
9.1 Precipitation on surface water
Supporting Information
The total volume of precipitation on surface water in the 2010–11 year is 112,395 ML. The following tables provide a summary and breakdown of precipitation on the surface water assets in the Sydney region.
Surface water asset |
Precipitation during 2010–11 (ML) |
Storages managed by the Sydney Catchment Authority |
97,242 |
Storages not managed by the Sydney Catchment Authority |
4,879 |
River sections |
10,274 |
Total |
112,395 |
Storage1 |
Precipitation during 2010–11 (ML) |
Cataract |
7,918 |
Cordeaux |
6,470 |
Avon |
8,774 |
Nepean |
3,763 |
Woronora |
1,914 |
Lake Burragorang (Warragamba Dam) |
43,733 |
Prospect |
3,763 |
Wingecarribee |
5,722 |
Fitzroy Falls |
7,531 |
Lake Yarrunga (Tallowa Dam) |
7,110 |
Blue Mountains1 |
544 |
Total |
97,242 |
1 Blue Mountains storages include Medlow Reservoir, Greaves Creek Reservoir, Upper Cascade Reservoir, Middle Cascade Reservoir and Lower Cascade Reservoir.
Storage1 |
Precipitation during 2010–11 (ML) |
Bamarang |
701 |
Danjera |
893 |
Flat Rock Creek |
274 |
Pejar |
1,477 |
Sooley |
1,020 |
Farmers Creek No. 2 |
97 |
Bundanoon |
171 |
Medway |
246 |
Total |
4,879 |
1 Data for storages not listed in the above tables are not available. Precipitation for those reservoirs has been considered with line item 9.4 Runoff to surface water.
River1 |
From |
To |
Precipitation during 2010–11 (ML) |
Capertee |
Glen Davis |
Upper Colo |
1,066 |
Coxs |
Lithgow |
Kelpie Point |
1,683 |
Macdonald |
Howes Valley |
St Albans |
138 |
Shoalhaven |
Kadoona |
Fossickers Flat |
3,059 |
Wollondilly |
Pomeroy |
Golden Valley |
4,328 |
Total |
10,274 |
1 Only the river sections for which river volumes have been calculated are included. Precipitation for all the other river reaches has been considered with line item 9.4 Runoff to surface water.
Quantification Approach
Bureau of Meteorology
Data Source
Provided by
Method
The Bureau provided precipitation data for following storages not managed by the Sydney Catchment Authority (SCA) :
- Bamarang Reservoir
- Danjera Reservoir
- Flat Rock Creek Reservoir
- Pejar Reservoir
- Sooley Reservoir
- Farmers Creek No. 2.
Precipitation for the river sections in:
- Capertee River
- Coxs River
- Macdonald River
- Shoalhaven River
- Wollondilly River.
Monthly precipitation data were produced by the Bureau. These were based on daily data from approximately 6,500 rain gauge stations and interpolated to a 0.05 degree (approximately 5 km) national grid (Jones et al. 2007)
The precipitation at each waterbody was estimated from the proportionally weighted average of gridpoints that intersected each water feature. The volume was then estimated using the surface area of each waterbody. The surface area varied dynamically with changing storage level for stoarges where the relationship between storage level and surface area had been derived.
Assumptions, Limitations, Caveats and Approximations
- The precipitation estimates were subject to approximations associated with interpolating observation point data to a national grid detailed in Jones et al. (2007).
- The dynamic storage surface areas calculated from the levels and capacity tables represent a monthly average and therefore will not capture changes that occur on a shorter temporal scale.
Uncertainty Information
The uncertainty estimate was not quantified.
Sydney Catchment Authority
Data Source
Provided by
Method
Precipitation for the following storages are managed by SCA:
- Cataract Reservoir
- Cordeaux Reservoir
- Avon Reservoir
- Nepean Reservoir
- Woronora Reservoir
- Lake Burragorang (Warragamba Dam)
- Prospect Reservoir
- Wingecarribee Reservoir
- Fitzroy Falls Reservoir
- Lake Yarrunga (Tallowa Dam)
- Blue Mountains reservoirs
– Medlow Reservoir
– Greaves Creek Reservoir
– Upper Cascade Reservoir
– Middle Cascade Reservoir
– Lower Cascade Reservoir.
Rainfall received over the entire catchment area was calculated by interpolating rainfall values from point gauges (primarily tipping-bucket rain gauges). Rainfall volumes over storages were calculated by multiplying relevant surface areas and interpolated rainfall values.
Assumptions, Limitations, Caveats and Approximations
Catchment average rain assumed to fall on the surface of a lake.
Uncertainty Information
The precipitation volume is based on measured data. Estimated uncertainty based on accuracy of rain gauges, limitations in the calculation method and organisational practice is +/– 10%.
Comparative year
The following table compares the value for the 2009–10 year reported in this account with the corresponding value reported in the 2010 Account.
2011 Account line item |
2010 Account line item |
Value reported in the 2010 Account (ML) |
Value reported in the 2011 Account (ML) |
Additional information |
9.1 Precipitation on surface water |
13.1 Precipitation on connected surface water |
83,203 |
83,203 |
Change in line item name |