Sydney

   

Quantification approach  

Quantification approaches are provided separately for the following inputs used to calculate outflow to the sea:

• rule-based environmental flow releases
• unspecified releases and spills from reservoirs and weirs to downstream rivers
• natural streamflows in gauged streams
• natural streamflows in ungauged streams
• treated water releases from wastewater treatment plants
• downstream diversions from flow leading to sea.

 

Quantification approach for rule-based environmental flow releases

 

Data source

Daily Return System (DRS) database.

 

Data provider

The Sydney Catchment Authority.

 

Method

Known release rates from flow meters, orifice plates, valves with rating tables or measured outlets were used to derive the volume.

 

Uncertainty

The volume is based on measured data. Estimated uncertainty based on meter accuracy, and professional judgment on rating tables and site configuration issues is +/–10%.

 

Approximations, assumptions, caveats/limitations

Nil.

 

Quantification approach for unspecified releases and spills from reservoirs and weirs to downstream rivers

 

Data source

Agency	Data source
The Bureau of Meteorology	Spilling volume from Danjera Reservoir for 2009–10 was estimated using the following input data: estimated precipitation and evaporation, and modelled inflow to Danjera Reservoir using Bureau of Meteorology data storage volumes of the reservoir provided by Shoalhaven City Council (source: Level monitoring at the reservoirs with hydrometric sensors linking to council’s radio telemetry system) diversions and other losses for the reservoir provided by Shoalhaven City Council (source: Shoalhaven City Council Telemetry System and daily data registers in respect of the operations of water treatment plants).
The Sydney Catchment Authority	Sydney Catchment Authority Hydstra system and Daily Return System (DRS) databases

 

 

Data provider

Agency	Data provider
The Bureau of Meteorology	Spilling volume from Danjera Reservoir
The Sydney Catchment Authority	Spilling volumes and other releases from the storage reservoirs and weirs managed by the authority

 

 

Method

Agency	Method
The Bureau of Meteorology	Reservoir mass balance calculations using measured storage volumes, estimated precipitation and evaporation, and modelled run-off
The Sydney Catchment Authority	Spill volumes derived from water levels and rating tables for spillways

 

 

Uncertainty

Agency	Uncertainty
The Bureau of Meteorology	The volume was estimated from measured and modelled data. Estimated uncertainties for some of the inputs used for the calculation of spilling volume from Danjera Reservoir are ungraded. These inputs are precipitation, evaporation and modelled run-off. Therefore, uncertainty for the spilling volume from Danjera Reservoir is ungraded. Estimated uncertainty for storage volume, which was the remaining input for the calculation, is +/–5%.
The Sydney Catchment Authority	The volume is based on measured data. Estimated uncertainty based on meter accuracy, and professional judgment on rating tables, site configuration issues and local issues at the time of spilling at each site is +/–5% to +/–10%.

 

 

Approximations, assumptions, caveats/limitations

Agency	Approximations, assumptions, caveats/limitations
The Bureau of Meteorology	Based on data provided by Shoalhaven City Council, water was not supplied from Danjera Reservoir during 2009–10. Reservoir losses other than spills have been assumed as negligible. For other approximations and assumptions, see the following line items: 13.1 for precipitation  13.4.1 for inflow  14.1 for evaporation.
The Sydney Catchment Authority	Nil.

 

Quantification approach for natural streamflows in gauged streams

 

 

Data source

Stream gauge data from the Hydstra system.

 

Data provider

The Sydney Catchment Authority.

 

Method

River levels are gauged and converted to a flow rate using a rating table. Rating tables are updated by manual stream gauging.

Some of the gauging sites have been linked to the Sydney Catchment Authority’s (SCA) radio telemetry system so that gauging data are readily available. For the other sites, data are downloaded to SCA’s Hydstra system in regular intervals from logged data at the site.

 

Uncertainty

The volume is based on measured data. Estimated uncertainty based on measurement accuracy and professional judgment on rating tables is +/–10% to +/–50%, depending on the site characteristics and flow rate.

 

Approximations, assumptions, caveats/limitations

Nil.

 

Quantification approach for natural streamflows in ungauged streams

 

Data source

The Bureau of Meteorology modelled the landscape water balance to estimate inflows using following data sources:

• the Bureau: climate data and geographic information system (GIS) layers
• Commonwealth Scientific and Industrial Research Organisation (CSIRO): raster spatial data, WaterDyn and AWRA-L model parameters, and radiation data
• NSW Office of Water: GIS data on waterbody and river channel sections
• SCA: GIS data on its operation area
• Geoscience Australia: built-up areas and other GIS layers.

 

Data provider

The Bureau of Meteorology (the Bureau)

 

Method

The Bureau calculated natural streamflow for the following ungauged and tidal rivers:

• the Hawkesbury River and the lower Nepean River, except catchment areas upstream of
• • Warragamba River at Lake Burragorang (Warragamba Dam) (Gauge No. 212243)
  • Pheasants Nest Weir (Gauge No. 212203)
  • Broughtons Pass Weir (Gauge No. 212233)
  • Macdonald River at St Albans (Gauge No. 212228)
  • Colo River at Upper Colo (Gauge No. 212290)
  • Gross River at Burralow (Gauge No. 212291)
  • South Creek at Richmond Road (Gauge No. 212297)
• northern Sydney rivers
• southern Sydney rivers, except the catchment area upstream of the Woronora River at Needles North Engadine (Gauge No. 213211)
• the Illawarra rivers
• the Shoalhaven River, except the catchment area upstream of Grassy Gully No. 2 (Gauge No. 215216).

Natural river flow in the river reaches is based on landscape water draining into the rivers modelled by the Bureau (see the method described for run-off to Line item 13.4.1 River reaches not within SCA operational area and the reservoirs).

 

Uncertainty

The volume is based on modelled and estimated data. Uncertainty is ungraded.

 

Approximations, assumptions, caveats/limitations

See in Line item 13.4.1 River reaches not within SCA operational area and the reservoirs.

 

Quantification approach for treated water releases from wastewater treatment plants

See Line item 13.7.1 Urban wastewater discharge to connected surface water and Line item 13.7.2 Urban recycled water discharge to connected surface water.

 

Quantification approach for downstream diversions from flow leading to sea

See the following:

• Line item 14.5.1 Surface water diversion – riparian right for diversion associated with riparian right
• Line item 14.6.5.4 Diversion of unregulated flows – urban holder for diversions by Sydney Water Corporation from the Hawkesbury River
• Line item 14.6.5.5 Surface diversion of unregulated flows – individual holder for stock and domestic diversions
• Line item 14.6.5.6 Surface diversion of unregulated flows – other lumped holders for diversions associated with other access licences.