Sydney
1.2 Unregulated river

Details of the volume of water stored in unregulated river channels are shown in the following table. The volume is an instantaneous estimate of static volume held in the river reaches. It is not the total volume flowing past a point during the 2011 Account.

Breakdown of rivers of the Sydney region

River1	From	To	Volume (ML) 30 June 2010	Volume (ML) 30 June 2011
Capertee	Glen Davis	Upper Colo	247	302
Coxs	Lithgow	Kelpie Point	76	191
Macdonald	Howes Valley	St Albans	2	277
Shoalhaven	Kadoona	Grass Gully No. 22	1,047	1,029
Wollondilly	Jooriland3	Golden Valley	93	406
Total			1,465	2,205

¹ Only the river sections for which data are available are included. Information about the river sections that were identified as water assets but could not be quantified is provided in 'Water assets and water liabilities that fail the recognition criteria'.

² The volume stated for the Shoalhaven River on 30 June 2010 includes the volume of water that was quantified between the gauging sites of Grass Gully No. 2 and Fossikers Flat. Fossikers Flat is further downstream from Grass Gully No. 2 and this volume contributed approximately 24% of the total volume for 30 June 2010. These data were not available during the 2010–11 year and therefore the volume stated on 30 June 2011 does not include the volume of water between these two sites.

³ The volume stated for the Wollondilly River on 30 June 2010 includes the volume of water that was quantified between the gauging sites of Pomeroy and Jooriland. Pomeroy is upstream of Jooriland and this volume contributed approximately 16% of the total volume for 30 June 2010. These data were not available during the 2010–11 year and therefore the volume stated on 30 June 2011 does not include the volume of water between these two sites.

NSW Office of Water: Hydstra and Computer Aided Improvements to River Operations (CAIRO) databases.

NSW Office of Water.

Derived from measured data.

For each river section S(n):

V = Q × T

The river channel storage will be equal to the sum of all river section volumes.

River channel storage = å S(n) V

Formula symbols

Symbol	Variable	Unit
Q	Average flow in the river section; calculated by averaging the daily flows at the upstream and downstream river gauges	ML/d
V	Volume in each river section	ML
T	Average travel time for a parcel of water to travel through the river section	days

• Travel times are estimated to the nearest day.
• Daily flow change between gauging sites is assumed to be linear.

Volume of water stored in the unregulated river channel has not been estimated for the following rivers because reliable data are not available:

• Hawkesbury and Nepean rivers except

         – Capertee River from Glen Davis to Upper Colo

         – Coxs River from Lithgow to Kelpie Point

         – Macdonald River from Howes Valley to St Albans

         – Wollondilly River from Jooriland to Golden Valley

• Shoalhaven River, except the reach from Kadoona to Grass Gully No. 2
• northern Sydney rivers
• southern Sydney rivers
• Illawarra rivers.

The volume was estimated from measured data. Estimated uncertainty is in the range +/– 50%, based on professional judgment with conservative uncertainty estimates of +/– 10% and +/– 50% for flow data and travel time, respectively.

The following table compares the value at 30 June 2010 reported in this account with the corresponding value reported in the 2010 Account.

 

Comparative information from the 2010 Account for line item 1.2

2011 Account line item	2010 Account line item	Value reported in the 2010 Account (ML)	Value reported in the 2011 Account (ML)	Additional information
1.2 Unregulated river	1.2 Unregulated channel	1,465	1,465	Change in line item name