DEECA Victorian Water Accounts 2022-23

About the area

The Barwon River rises in the forested Otway Ranges. It flows through the townships of Birregurra, Winchelsea and Inverleigh, where it is joined by the Leigh River, before joining the Moorabool River and flowing through Geelong and the Lower Barwon Wetlands, reaching the coast at Barwon Heads.

Annual rainfall in the basin is between 600-1800 mm in the headwaters and reduces to 400-600 mm in the lower reaches.

More information on water management and accounting is detailed in Water explained.

2022-23 overview

Available water

Catchment inflow was higher than the previous year.

Licensed diversion restrictions

There was a similar level of restrictions on licensed diversions as the previous year.

Water use

More water was diverted for consumptive purposes than the previous year.

When compared to the previous year, in 2022-23:

more rainfall was received
catchment inflow was much higher, the largest volume received in the last 18 years
levels in the major storages ended the year lower
there was a similar level of restrictions on licensed diversions from unregulated streams
more water was diverted from the basin for consumptive uses.

Climate

Rainfall

In 2022-23, rainfall across the Barwon basin was higher than the previous year. Rainfall was:

very much above the long-term average in the upper Leigh catchment from around Ballarat to Wingeel Swamp, and along the western border towards Gellibrand
above average over rest of the basin from Salt Lake and West Barwon Reservoir to the Bellarine Peninsula.

Figure 1 displays the rainfall received in 2022-23 compared to the long-term average (1975-2023).

Figure 1: Rainfall deciles, Barwon basin

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Sourced from the Australian Bureau of Meteorology

River basin water balance

This section describes the known and estimated inflows, outflows and change of storage volumes in the basin.

Of the total inflows, 89% flowed out into the ocean in 2022-23.

Water balance

The table below shows the total volumes of water available and supplied from water resources in the Barwon basin in 2022-23.

Table 1: Water balance, Barwon basin

Water account component	2021-22 (ML)	2022-23 (ML)
Major on-stream storage
Volume in storage at start of year	32,945	31,487
Volume in storage at end of year	31,487	25,775
Change in storage	(1,458)	(5,712)
Inflows
Catchment inflow ¹	190,207	456,181
Rainfall on major storages	2,909	3,623
Inflows from the Moorabool River	39,785	160,392
Transfers from the Corangamite basin via Woady Yaloak Channel	0	0
Transfers from Moorabool basin to White Swan Reservoir ²	5,305	8,335
Transfers from Campaspe basin to White Swan Reservoir	0	0
Treated wastewater discharged back to river	10,583	13,009
Total inflows	248,789	641,540
Outflows
Diversions
Urban diversions	41,329	43,815
Licensed diversions from unregulated streams	703	420
Small catchment dams	6,566	10,623
Total diversions	48,598	54,858
Losses
Evaporation from major storages	2,758	2,492
Net evaporation from small catchment dams	4,241	5,075
In-stream infiltration to groundwater, flows to floodplain and evaporation	10,078	10,861
Total losses	17,077	18,428
Water passed at outlet of basin
River outflows to the ocean	184,573	573,967
Total water passed at outlet of basin	184,573	573,967
Total outflows	250,248	647,253

Water account component	2021-22 (ML)	2022-23 (ML)
Major on-stream storage
Volume in storage at start of year	32,945	31,487
Volume in storage at end of year	31,487	25,775
Change in storage	(1,458)	(5,712)
Inflows
Catchment inflow ¹	190,207	456,181
Rainfall on major storages	2,909	3,623
Inflows from the Moorabool River	39,785	160,392
Transfers from the Corangamite basin via Woady Yaloak Channel	0	0
Transfers from Moorabool basin to White Swan Reservoir ²	5,305	8,335
Transfers from Campaspe basin to White Swan Reservoir	0	0
Treated wastewater discharged back to river	10,583	13,009
Total inflows	248,789	641,540
Outflows
Diversions
Urban diversions	41,329	43,815
Licensed diversions from unregulated streams	703	420
Small catchment dams	6,566	10,623
Total diversions	48,598	54,858
Losses
Evaporation from major storages	2,758	2,492
Net evaporation from small catchment dams	4,241	5,075
In-stream infiltration to groundwater, flows to floodplain and evaporation	10,078	10,861
Total losses	17,077	18,428
Water passed at outlet of basin
River outflows to the ocean	184,573	573,967
Total water passed at outlet of basin	184,573	573,967
Total outflows	250,248	647,253

Major on-stream storages

Major - greater than 1,000 ML - on-stream storages in the Barwon basin are included in the water balance. Volumes in off-stream storages are presented for additional information about the resource condition.

Storage levels

Major storage levels in the Barwon basin were 68% on 30 June 2023.

Lower than the previous year

Storage levels were 83% on 30 June 2022.

Table 2: Storage levels, Barwon basin

Storage	Total capacity (ML)	Start volume in store (ML)	Rainfall (ML)	Evaporation (ML)	Catchment inflow less regulated releases (ML)	End volume in store (ML)
On-stream storages
Gong Gong Reservoir	1,902	1,338	241	206	(174)	1,199
West Barwon Reservoir	22,064	19,361	2,002	1,291	(6,730)	13,342
White Swan Reservoir ¹	14,107	10,788	1,380	995	61	11,234
Subtotal	38,073	31,487	3,623	2,492	(6,843)	25,775
Off-stream storages
Wurdee Boluc Reservoir	40,032	29,011	4,348	4,249	1,604	30,714
Total 2022-23	78,105	60,498	7,971	6,741	(5,239)	56,489
Total 2021-22	78,105	57,644	6,078	7,221	3,997	60,498

Storage	Total capacity (ML)	Start volume in store (ML)	Rainfall (ML)	Evaporation (ML)	Catchment inflow less regulated releases (ML)	End volume in store (ML)
On-stream storages
Gong Gong Reservoir	1,902	1,338	241	206	(174)	1,199
West Barwon Reservoir	22,064	19,361	2,002	1,291	(6,730)	13,342
White Swan Reservoir ¹	14,107	10,788	1,380	995	61	11,234
Subtotal	38,073	31,487	3,623	2,492	(6,843)	25,775
Off-stream storages
Wurdee Boluc Reservoir	40,032	29,011	4,348	4,249	1,604	30,714
Total 2022-23	78,105	60,498	7,971	6,741	(5,239)	56,489
Total 2021-22	78,105	57,644	6,078	7,221	3,997	60,498

Inflows

Catchment inflow

Catchment inflow represents the volume of water flowing into the waterways of a basin. It is calculated as the total outflows and change in storage minus the known inflows.

Large rainfall events across much of the state in October 2022 resulted in high flows, which impacted the ability of gauges to provide accurate streamflow estimates for the Barwon basin. This impacted the estimates of catchment inflows, end of basin outflows and losses in this basin. Alternative methods have been required, which have a lower confidence than the method typically used. However, these methods are considered fit for this purpose of basin-scale water accounting.

An explanation of the methods applied can be found in the method tab of Figure 3.

Above average inflows of 456,181 ML were received (184% of the long-term average of 248,000 ML), much more than the previous year (77% of the long-term average). This was reflective of the very much above average rainfall received across the basin in 2022-23.

Above average inflow received

Catchment inflow was 184% of the long-term average of 248,000 ML.

Much more water received than the previous year

Catchment inflow was much more than the previous year (77% of the long-term average).

This section describes alternative methods for estimating streamflows that were applied in the 2022-23 Accounts to address challenges resulting from high flows events.

Each year for the Accounts, DEECA uses streamflow data from several representative gauges on the Water Measurement Information System (WMIS). This is used to estimate the end of basin outflows for each basin, and to estimate the in-stream losses in those basins for which DEECA has an appropriate loss model.

The streamflow data also influences the estimate of catchment inflows, which is the balancing item in the water balance (end of basin outflows plus diversions minus known inflows).

In most years, it is common for DEECA to ask the data provider to infill some of the data using correlation with nearby similar gauges (with a correlation coefficient above 0.950) where there are small gaps that are likely to be inconsequential for the annual total streamflow. The correlation procedure is aligned with AS3778.2.3-2001: Australian Standard for Measurement of water flow in open channels.

However, during the October 2022 high flow events across many Victorian systems, several water monitoring sites recorded river heights which exceeded the upper range of the available rating table (which is used to convert river height to streamflow using established relationships). The suitability of extrapolating a rating table past its upper range is governed by Australian Standard AS3778.2.3, which provides that ratings can be extrapolated up to 1.5 times their maximum gauged flow, based on a logarithmic trend. For the sites considered, this range would still be insufficient to cover the flood peaks recorded.

The data provider was required to work outside its usual procedure for correlation with other local sites to estimate total flow in one or more sites of this basin. This may have involved a theoretical assessment of the flow capacity beyond what had been measured, based on the water monitoring site’s cross-section, to determine whether streamflow remained contained within the river channel during the event, or where break out occurred, and what losses may need consideration.

Consultation with hydrology specialists independent of the data provider has determined that the methods applied are the best available at the time given the data challenges, and that these are fit for the purpose of estimating annual water balances. The approach used is consistent with that applied in previous years such as the 2010-11 floods.

Data produced for the Accounts that fell outside the traditional method of correlation may be found in the sites Hydstra archive under variable ***.42. (100.42 and 141.42) The .42 variable was created to preserve the work calculated as part of this project and for future years where we may experience similar unprecedented weather patterns where data infilling is required. By documenting these in the archive, it will remain available for future calculations and checks.

Better data for other purposes may become available at a later date, given time for more in-depth modelling.

Wastewater treatment plants

Water treated at wastewater treatment plants can be used to supplement water available in the basin. Water discharged to waterways from treatment plants is included as an inflow to the water balance.

Information on treatment plants is reported in the water supply local reports for the water corporation responsible for managing the plant.

In this basin, wastewater treatment plants are managed by Central Highlands Water and Barwon Water.

Outflows

Diversions

In 2022-23, 54,858 ML of water was diverted for consumptive uses: town, domestic and stock, irrigation and commercial supply. This is more than the 48,597 ML diverted in the previous year. While an increase in use was reported, urban and licensed diversions were similar to the previous year. The overall increase in consumptive use is due to the 4,057 ML increase in the estimation of small catchment dam use volume.

Small catchment dams

Water harvested, used and lost by small catchment dams (farm dams) is included in the water balance.

Table 3: Small catchment dams, Barwon basin

Type of small catchment dam	Capacity (ML)	Usage (ML)	Net evaporation (ML)	Total water harvested (ML)
Domestic and stock (not licensed)	24,163	7,434	4,237	11,671
Registered/licensed commercial and irrigation	9,746	3,189	838	4,027
Total 2022-23	33,909	10,623	5,075	15,698
Total 2021-22	33,909	6,566	4,241	10,807

Type of small catchment dam	Capacity (ML)	Usage (ML)	Net evaporation (ML)	Total water harvested (ML)
Domestic and stock (not licensed)	24,163	7,434	4,237	11,671
Registered/licensed commercial and irrigation	9,746	3,189	838	4,027
Total 2022-23	33,909	10,623	5,075	15,698
Total 2021-22	33,909	6,566	4,241	10,807

Entitlements and compliance

Entitlements provide the basis for how water is shared in the basin.

Entitlement volumes

Rights to water in the Barwon basin are shown in Table 4.

Entitlement volumes represent a maximum volume of water that can be taken in a one-year period. The volume available in a particular year is dependent on the rules for allocating water set out in the entitlement and the seasonal conditions in that year, which can vary. The rules for allocating water under an entitlement differ between entitlements and systems. This affects the ability and likelihood of water being taken in a particular year.

Table 4: Annual entitlement volumes at 30 June, Barwon basin

Water entitlement - Barwon basin	2021-22 (ML)	2022-23 (ML)
Bulk Entitlements (Upper Barwon System) Conversion Order 2002 ¹	42,466	42,466
Bulk Entitlement (Yarrowee-White Swan System) Conversion Order 2002 ²	12,267	12,267
Barwon River Environmental Entitlement 2011 ³	n/a	n/a
Upper Barwon River Environmental Entitlement 2018 ⁴	n/a	n/a
Take and use licences - unregulated surface water	4,618	4,618
Licensed small catchment dams - on-waterway	923	923
Licensed small catchment dams - off-waterway	8,823	8,822
Total	69,097	69,096

Water entitlement - Barwon basin	2021-22 (ML)	2022-23 (ML)
Bulk Entitlements (Upper Barwon System) Conversion Order 2002 ¹	42,466	42,466
Bulk Entitlement (Yarrowee-White Swan System) Conversion Order 2002 ²	12,267	12,267
Barwon River Environmental Entitlement 2011 ³	n/a	n/a
Upper Barwon River Environmental Entitlement 2018 ⁴	n/a	n/a
Take and use licences - unregulated surface water	4,618	4,618
Licensed small catchment dams - on-waterway	923	923
Licensed small catchment dams - off-waterway	8,823	8,822
Total	69,097	69,096

Available water and take under entitlements

Total water available under entitlements represents the volume of water that was available to be taken by entitlement holders in 2022-23. The volume includes carryover from the previous year, seasonal allocations and net trade into the basin.

Water taken

There was 47,961 ML used in 2022-23, similar to the previous year (44,819 ML).

Restrictions on licensed diversions from unregulated streams

A Stage 2 roster was in place in Zone A of the Barwon River during July-August 2022.
All other streams were unrestricted during 2022-23.
During the previous year, there was also a Stage 2 roster in place in Zone A of the Barwon River from April-June 2022.

Available water and take table

This table shows the volume of available water and the volume taken under entitlements in 2022-23.

More information on available water and take has been detailed in How we account for surface water.

In 2022-23, a similar volume of water was taken under entitlements as the previous year.

Table 5: Available water and take under entitlements, Barwon basin

Water entitlement - Barwon basin	Available water (ML)	Water taken (ML)
Upper Barwon system ¹	-	42,466	0	42,466	32,683
Yarrowee-White Swan system	-	12,267	0	12,267	11,133
Barwon River Environmental Entitlement ²	-	-	-	-	-
Upper Barwon River Environmental Entitlement ³	2,000	165	0	2,165	536
Take and use licences - unregulated surface water	-	4,618	90	4,708	420
Licensed small catchment dams	-	9,746	(90)	9,656	3,189
Total 2022-23	2,000	69,262	0	71,262	47,961
Total 2021-22	830	71,116	0	71,946	44,819

Water entitlement - Barwon basin	Available water (ML)	Water taken (ML)
Upper Barwon system ¹	-	42,466	0	42,466	32,683
Yarrowee-White Swan system	-	12,267	0	12,267	11,133
Barwon River Environmental Entitlement ²	-	-	-	-	-
Upper Barwon River Environmental Entitlement ³	2,000	165	0	2,165	536
Take and use licences - unregulated surface water	-	4,618	90	4,708	420
Licensed small catchment dams	-	9,746	(90)	9,656	3,189
Total 2022-23	2,000	69,262	0	71,262	47,961
Total 2021-22	830	71,116	0	71,946	44,819

Compliance

Compliance against water entitlements is reported for this basin in 3 areas:

entitlement issued: that the volume of entitlements issued in a basin does not exceed formal caps, and has not increased without appropriate approvals
water taken: that the volume of water taken during the year does not exceed the volume considered to be available for consumptive and/or in-stream use during that year
bulk entitlement provisions: that holders of entitlements do not breach any provisions that are documented in their bulk entitlement orders.

Total entitlement volume

There was no net increase in the total entitlement volume from the previous year.

Total volume diverted

The total volume diverted (47,961 ML) was within the volume available for the year (71,262 ML).

Individual bulk entitlements

No individual bulk entitlement holder took more than the annual volume made available to them.

Exceptions to compliance

Individual bulk entitlement holders complied with all provisions in their entitlements. However, one compliance difficulty was reported. See note below.

Note to compliance difficulties:

The Victorian Environmental Water Holder (VEWH) reported one metering plan for the Upper Barwon River Environmental Entitlement 2018 as incomplete. DEECA has agreed to extend the deadline for completion of the Upper Barwon River Environmental Entitlement 2018 metering plan until at least 2024-25, at which time VEWH will be required to submit updated metering plans for all entitlements with metering plan obligations, to comply with new guidelines that have been developed by DEECA. The agreed time extension is to enable the water corporation metering plans to be developed first.

Water for the environment

Environmental watering sites

Environmental watering sites and environmental values in the Barwon basin that depend on water for the environment include:

the Bellarine Peninsula’s internationally significant wetlands, which are listed under the Ramsar Convention and which rely on freshwater inputs from the Barwon basin to function ecologically
the Lake Connewarre complex
native fish populations (such as Australian grayling, Yarra pygmy perch, Australian mudfish and tupong)
the native waterbird population (particularly migratory shorebirds including the common greenshank, Pacific golden plover, curlew sandpiper and red-necked stint)
platypus populations in the upper and middle catchment.

Environmental water reserve

In 2022-23, water for the environment in the Barwon basin comprised:

the Barwon River Environmental Entitlement 2011
the Upper Barwon River Environmental Entitlement 2018, comprising 3.8% of inflows to West Barwon Reservoir held by the VEWH
water from the Ballarat South Wastewater Treatment Plant released into the Leigh and Barwon rivers
a portion of the treated groundwater discharged from the Fyansford quarry to the lower Moorabool River
water set aside for the environment through the operation of passing flow conditions:
- on consumptive bulk entitlements held by Barwon Water and Central Highlands Water
- on licensed diversions
all other water in the basin not allocated for consumptive uses: this water also provides social, recreational and cultural benefits.

Environmental water use

In 2022-23, a total of 536 ML of environmental water was delivered in-stream in the Barwon basin.

Management responsibilities

Management of water in the Barwon basin is undertaken by various parties

Authority	Management responsibilities
Southern Rural Water	Managing surface water licensed diversions.
Barwon Water	Supplying urban water to Geelong and surrounding towns by sourcing water from the Moorabool basin and from the Melbourne system via the Melbourne to Geelong Pipeline. Operating West Barwon Reservoir and Lake Wurdee Boluc.
Central Highlands Water	Supplying urban water to Ballarat and surrounding towns, mainly with water sourced from the Moorabool basin and the Campaspe and Goulburn basins, via the Goldfields Superpipe. Operating White Swan and Gong Gong reservoirs.
Corangamite Catchment Management Authority	Managing waterway and catchments across the entire Barwon basin.

Water supply system	2021-22 (ML)	2022-23 (ML)
Geelong/Bellarine	32,396	32,683
Greater Ballarat system	8,933	11,133

Nearby basins

Corangamite

Explore the Corangamite river basin.

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Moorabool

Explore the Moorabool river basin.

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Water entitlement - Barwon basin	Available water (ML)				Water taken (ML)
Water entitlement - Barwon basin	Opening carryover	Allocation issued	Net trade in / (out)	Total water available	Water taken (ML)
Upper Barwon system ¹	-	42,466	0	42,466	32,683
Yarrowee-White Swan system	-	12,267	0	12,267	11,133
Barwon River Environmental Entitlement ²	-	-	-	-	-
Upper Barwon River Environmental Entitlement ³	2,000	165	0	2,165	536
Take and use licences - unregulated surface water	-	4,618	90	4,708	420
Licensed small catchment dams	-	9,746	(90)	9,656	3,189
Total 2022-23	2,000	69,262	0	71,262	47,961
Total 2021-22	830	71,116	0	71,946	44,819

Barwon

On this page:

In this area

About the area

2022-23 overview

Available water

Licensed diversion restrictions

Water use

Climate

Rainfall

Figure 1: Rainfall deciles, Barwon basin

River basin water balance

Water balance

Table 1: Water balance, Barwon basin

Major on-stream storages

Storage levels

Lower than the previous year

Table 2: Storage levels, Barwon basin

Inflows

Catchment inflow

Above average inflow received

Much more water received than the previous year

Wastewater treatment plants

Outflows

Diversions

Small catchment dams

Table 3: Small catchment dams, Barwon basin

Entitlements and compliance

Entitlement volumes

Table 4: Annual entitlement volumes at 30 June, Barwon basin

Available water and take under entitlements

Water taken

Restrictions on licensed diversions from unregulated streams

Available water and take table

Table 5: Available water and take under entitlements, Barwon basin

Compliance

Total entitlement volume

Total volume diverted

Individual bulk entitlements

Exceptions to compliance

Water for the environment

Environmental watering sites

Environmental water reserve

Environmental water use

Management responsibilities

Nearby basins

Corangamite

Moorabool

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Victorian Water Accounts 2022-23

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