Canberra: Statement details
Runoff associated with rainfall from an east coast low event in early June 2016 was the primary reason storage volumes were 83% full at 30 June 2016 compared to 80% full at the start of the year. Prior to this event, streamflow and storage inflows across the region were relatively low.
Water assets
Surface water assets
Surface water asset volumes in the Canberra region at 30 June 2016 were 273,135 ML, which comprised water held in storages (233,562 ML) and lakes (39,573 ML). The location of each storage within the region and the volume of water in each storage as a percentage of total storage capacity at the end of the year is shown in Figure S1.
The volume of water in rivers, and some lakes and wetlands could not be quantified due to a lack of available data.
Figure S1 Percentage-full volume on 30 June 2016 for each storage
The overall storage volume within the Canberra region increased during the 2015–16 year from 80% to 83% full at 30 June 2016 (Figure S2). This was largely due to heavy rainfall associated with an east coast low event that occurred 5–6 June 2016, which caused very high streamflows and storage inflows for the remainder of the 2015–16 year (see Climate and water). Prior to this event, the total storage volume was less than that at the start of the 2015–16 year.
It should be noted that the Googong Reservoir has been full, or near full, since the conclusion of the Millennium Drought in late 2010. Googong is the region’s secondary source of water after the upper Cotter River (Corin and Bendora reservoirs). In normal and wet periods, most of the region’s water supply comes from the upper Cotter River due to comparatively less production cost and better water quality. Googong Reservoir has remained full since 2010 as conditions have not been dry enough to require large volumes of water to be sourced from the reservoir.
Further information on the individual storages within the region is available on the Bureau of Meteorology's Water Storage website.
Figure S2 Total storage volume in the region at 30 June 2016 compared with the previous 6 years
There are three primary lakes within the Canberra region: Lake Burley Griffin, Lake Ginninderra, and Lake Tuggeranong. The lakes are primarily used for recreation, conservation, and aesthetic purposes and are not formally associated with the urban water supply system; however, water can be abstracted or released to maintain environmental flows and for small-scale irrigation.
The location of each lake within the region and the volume of water in each lake as a percentage of total capacity at the end of the 2015–16 year is shown in Figure S3.
Figure S3 Percentage-full volume on 30 June 2016 for each major lake
Total volume of these three lakes at 30 June 2016 compared with the previous six years is shown in Figure S4.
Figure S4 Total lake volume at 30 June 2016 compared with the previous 6 years
Groundwater assets
The aquifers in the Canberra region are described in the Groundwater section of the 'Region description'. Given the majority of groundwater within the region is stored in fractured rock aquifers that are difficult to measure and monitor, the volume of water stored in the aquifers cannot be quantified, as indicated by dashes ('–') in the water accounting statements.
Water liabilities
Water liabilities in the Canberra region refer to the volume of allocation remaining on licence entitlements at the end of the 2015–16 year for:
- surface water: individual users—0 ML
- groundwater: individual users—0 ML.
There are no allocated surface water or groundwater licence entitlements in the ACT. For NSW portion of the region, according to the Water Sharing Plan for the Murrumbidgee Unregulated and Alluvial Water Sources, carryover of unused water allocation is allowed for licence holders; however, due to limited data availability the carryover volume could not be quantified. Therefore, for the purposes of the 2016 Account, it is assumed the entire unused portion of the allocation is forfeited and the allocation remaining is zero (tables S1–S2). The allocation (water liability increases), allocated abstraction (water outflow), and the adjustment and forfeiture (water liability decreases) for each licence entitlement is also provided.
A more detailed description of water allocations and associated water rights in the Canberra region is given in the Water rights note.
| Volume ML | |
| Opening balance at 1 July 2015 | 0 |
| Allocation | 1,832 |
| Allocated diversion | – |
| Adjustment and forfeiture | (1,832) |
| Closing balance at 30 June 2016 | 0 |
| Volume ML | |
| Opening balance at 1 July 2015 | 0 |
| Allocated | 851 |
| Allocation extraction | – |
| Adjustment and forfeiture | (851) |
| Closing balance at 30 June 2016 | 0 |
Water asset increases
Total water asset increases for the region (961,870 ML) comprised:
- surface water increases—923,224 ML
- urban water system increases—38,646 ML.
The key water asset increases for the region were runoff and inflow, which made up more than 94% of the total water asset increases. Runoff is climate-dependent and was greater than the previous year, primarily reflecting the high rainfall experienced across the region associated with the east coast low event in June 2016 (see Climate and water).
Urban water system increases represent wastewater collected, which generally changes little from year to year (see Urban water store note).
Water asset decreases
Total water asset decreases for the region (803,347 ML) comprised:
- surface water decreases—755,014 ML
- groundwater decreases—1,276 ML
- urban water system decreases—47,057 ML.
The key water asset decrease for the region was outflow, which made up more than 90% of the total water asset decreases. This flow is very climate-dependent and was higher than the previous year, which primarily reflects the high rainfall experienced across the region associated with the east coast low event in June 2016 (see Climate and water).
Urban water system decreases primarily relate to the supply system delivery: urban users. The delivery of water from this system generally change little from year to year.
Water flows
Total water inflows to the region (961,870 ML) and total water outflows from the region (803,347 ML) are equal to the volume of Water asset increases and Water asset decreases respectively, as given above.
A detailed description on all the water inflows associated with the surface water store, groundwater store and urban water system are provided in the Water stores note.
Unaccounted-for difference
The volume recognised in the water accounting statements (150,507 ML) represents the total unaccounted-for difference for the Canberra region for the 2015–16 year.
The unaccounted-for difference is the volume necessary to reconcile the opening water storage and closing water storage with the total water inflows and total water outflows reported in the water accounting statements. It is calculated according to Table S3.
| Volume ML | |
| Opening water storage balance at 1 July 2015 | 265,119 |
| Total inflows | 961,870 |
| Total outflows | (803,347) |
| Closing water storage balance at 30 June 2016 | (273,135) |
| Unaccounted-for difference | (150,507) |
The unaccounted–for difference can also be calculated by summing the volumes necessary to reconcile (balance) the opening and closing storage with the water inflows and outflows of each of the separate water stores of the region, as shown in Table S4.
| Volume ML | |
| Surface water store | (143,798) |
| Groundwater store | (3,178) |
| Urban water system | (3,531) |
| Unaccounted-for difference | (150,507) |
Table S4 shows that the unaccounted-for difference volume is primarily explained by the balancing item of the surface water store. The surface water balancing item is attributed to uncertainty associated with runoff and river outflow, and the volume of river and floodplain losses not being able to be quantified (see Surface water store note).