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National Water Account 2016

Ord: Statement details

Despite average annual rainfall for the year, below average rainfall during January–February, the typically wettest months of the year, contributed to low annual streamflows across the region. Storage volumes decreased from 91% to 74% full during the 2015–16 year, the second successive year water assets have dropped in the region.

 

 

Water assets

Surface water assets

Surface water asset volumes in the Ord region at 30 June 2016 were 8,072,764 ML, which comprised water held in storages (8,057,564 ML) and regulated rivers (15,200 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 unregulated rivers, lakes and wetlands could not be quantified due to a lack of available data; however, the volume of water held in channels and lakes is considered to be relatively small compared to the volume held in storages.

 

Figure S1 Map of percentage-full volume on 30 June 2016 for each storage
Figure S1 Percentage-full volume on 30 June 2016 for each storage

 

The volume of water in Lake Argyle makes up more than 98% of the total surface water storage in the region. The water volume in Lake Argyle decreased during the 2015–16 year from 91% to 73% full at 30 June 2016, which can be attributed to the below average inflows into Lake Argyle during the year (see Climate and water).

All other storages within the Ord region were more than 80% of capacity at 30 June 2016, bringing overall regional storage up to 74% of capacity (Figure S2). These smaller storage volumes remain relatively unchanged from year to year compared to Lake Argyle. More detailed information on the individual storages within the region is available on the Bureau of Meteorology's Water Storage website.

 

Figure S2 Graph of total storage volume in the region at 30 June 2016 compared with the previous 6 years
Figure S2 Total storage volume in the region at 30 June 2016 compared with the previous 6 years

 

Groundwater assets

The aquifers in the Ord region are described in the Groundwater section of the 'Region description'. While information exists on water movement to and from the aquifers (see Water stores note), volumes of water stored in the aquifers could not be quantified due to a lack of available data.

 

Water liabilities

Water liabilities in the Ord region refer to the volume of allocation remaining on licence entitlements at the end of the 2015–16 year. 

Most of the water supply licences for the region do not have a water management year that ends on 30 June. Therefore, the allocation remaining at the end of the 2015–16 year is the unused component of the annual allocation for these licence entitlements (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 Ord region is given in the Water rights note.

 

Table S1 Volume of surface water allocation remaining at 30 June 2016
 Individual users
(ML)
Urban system
(ML)
Irrigation scheme
(ML)
Opening balance at 1 July 201520,585669304,801
Allocation37,336775386,800
Allocated diversion(24,657)(433)(147,822)
Adjustment and forfeiture(14,402)(343)(233,017)
Closing balance at 30 June 201618,862668310,762

 

Table S2 Volume of groundwater allocation remaining at 30 June 2016
 Individual users
(ML)
Urban system
(ML)
Opening balance at 1 July 20151,1942,252
Allocated11,5892,700
Allocated extraction(6,740)(1,832)
Adjustment and forfeiture(4,836)(868)
Closing balance at 30 June 20161,2072,252

 

Water asset increases

Total water asset increases for the region (4,314,910 ML) comprised:

  • surface water increases—4,306,338 ML
  • groundwater increases—8,572 ML.

The key water asset increases for the region was runoff, which made up more than 95% of the total water asset increases. Runoff is very climate-dependent and was much less than the previous year, which reflects the poor wet season rainfall conditions experienced across the region for the second successive year (see Climate and water).

Groundwater increases represents recharge from the landscape, which generally changes little from year to year.

 

Water asset decreases

Total water asset decreases for the region (5,009,306 ML) comprised surface water flows only; groundwater flows from the aquifers could not be quantified due to a lack of available data.

The key water asset decreases for the region were outflow and evaporation, which made up approximately 60% and 40% of the total water asset decreases, respectively. Both of these flows are very climate-dependent, particularly outflow where the poor wet season rainfall across the region (see Climate and water) contributed to a greater than 20% decrease in river outflow to sea from the previous year.

 

Water flows

Total water inflows to the region (4,314,910 ML) is equal to the volume of Water asset increases above. Total water outflows from the region (5,190,790 ML) was marginally higher than the volume of Water asset decreases (5,009,306 ML) because the volume of water outflows also includes the flows corresponding to the accrual transactions, that is, the allocated diversions and extractions of water (see the Water liabilities section above).

A detailed description on all the water flows associated with the surface water and groundwater stores is provided in the Water stores note.

 

Unaccounted-for difference

The volume recognised in the water accounting statements (994,326 ML) represents the total unaccounted-for difference for the Ord 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.

 

Table S3 Calculation of unaccounted-for difference for the 2015–16 year
 Volume
ML
Opening water storage balance at 1 July 20159,942,970
Total inflows4,314,910
Total outflows(5,190,790)
Closing water storage balance at 30 June 2016(8,072,764)
Unaccounted-for difference(994,326)

 

The unaccounted–for difference can also be calculated by adding 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.

 

Table S4 Balancing volumes for the water stores of the Ord region for the 2015–16 year
 Volume
ML
Surface water store(994,326)
Groundwater store0
Unaccounted-for difference(994,326)

 

The volume of water in the groundwater stores within the Ord region could not be quantified. The Western Australian Department of Water, in managing groundwater in the region, estimates that the volume of recharge to groundwater was equivalent to the volume of extraction. Therefore the volume of the balancing item for the groundwater store is assumed to be 0 ML.