Ord
Water resources and systems
Introduction
The following set of notes provides consolidated reports for each of the water stores and systems within the Ord region during the 2012–13 year. The water stores and systems included in the region are shown in Figure 1.
For more information about the region, please refer to the General description section of the 'Contextual information'.
Figure 1 Schematic diagram of the water stores and systems within the Ord region
Information on all water flows to and from each water store and system are presented in this note, including between-store flows and transfers that are not presented in the water accounting statements. The between-store flows and transfers that occur in the region are presented in Figure 2.
The numbers on the diagram refer to the line item numbers in the water store notes. For each between-store flow, there are two line item numbers: one refers to flow out of a water store and the other refers to flow into a water store.
Figure 2 Schematic diagram of between-store flows that occur within the Ord region; line item numbers are provided next to the flows
The between-store flows and transfers (Figure 2), which are eliminated from the region's water accounting statements, are shown in italics throughout the following set of notes.
Surface water
A description of the Ord region's surface water resources is provided in the Surface water section of the 'Contextual information'.
The Statement of Water Assets and Water Liabilities for the surface water store (Table 1) shows that total surface water assets and net water assets decreased during the 2012–13 year in the Ord region.
Water assets | Volume at 30 June 2013 (ML) |
Volume at 30 June 2012 (ML) |
1 Surface water | ||
1.1 Storages | 8,577,385 |
10,759,396 |
1.2 Unregulated river | – |
– |
1.3 Regulated river | 17,238 |
16,385 |
1.4 Lakes and wetlands | – |
– |
Total surface water assets | 8,594,623 |
10,775,781 |
Water liabilities | ||
5 Surface water liability | ||
5.1 Surface water allocation remaining | 20,262 |
23,801 |
5.2 Surface water allocation remaining – urban water system | 670 |
670 |
5.3 Surface water allocation remaining – irrigation scheme | 270,673 |
282,202 |
Total surface water liabilities | 291,605 |
306,673 |
Opening net water assets | 10,469,108 |
14,844,260 |
Change in net water assets | (2,166,090) |
(4,375,152) |
Closing net water assets | 8,303,018 |
10,469,108 |
The volume of water in unregulated rivers (line item 1.2 Unregulated river) and lakes and wetlands (line item 1.4 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.
The location of each storage within the Ord region and the volume of water in each storage (including dead storage) as a percentage of total storage capacity at the end of the 2012–13 year is shown in Figure 3.
Figure 3 Location map of the storages within the Ord region; the percentage-full volume on 30 June 2013 for each storage is also shown
The water volume in Lake Argyle decreased during the 2012–13 year from 99% to 78% full at 30 June 2013 (see line item 1.1 Storages). The near capacity volume at the start of the 2012–13 year was due to the record rainfall conditions observed in the 2010–11 year, which resulted in high storage levels throughout the 2011–12 year (see line item note 1.1 in the 2012 Account). The storage volume in Lake Argyle during the last two years has been in steady decline since the record rainfall year because of relatively low inflows since then.
All other storages within the Ord region were more than 90% of capacity at 30 June 2013 (Figure 3).
The Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows for the surface water store are provided in tables 2 and 3 respectively.
Water asset increases | 2012–13 volume (ML) |
2011–12 volume (ML) |
9 Surface water increases | ||
9.1 Precipitation on surface water | 556,514 |
756,582 |
9.3 Groundwater discharge | – |
– |
9.4 Runoff to surface water | 2,171,758 |
6,794,954 |
9.5 Point return from irrigation scheme | – |
– |
9.6 Overbank flood return to river channel | – |
– |
9.9 Discharge from urban water system | 603 |
686 |
Total surface water increases | 2,728,875 |
7,552,222 |
Water liability decreases | ||
13 Surface water liability decreases | ||
13.1 Adjustment and forfeiture of surface water allocation | 14,446 |
14,266 |
13.2 Adjustment and forfeiture of surface water allocation – urban water system | 348 |
418 |
13.3 Adjustment and forfeiture of surface water allocation – irrigation scheme | 195,932 |
182,738 |
Total surface water liability decreases | 210,726 |
197,422 |
Water asset decreases | ||
17 Surface water decreases | ||
17.1 Evaporation from surface water | 1,488,640 |
1,663,087 |
17.2 River outflow from the region | 2,643,399 |
7,286,990 |
17.3 Leakage to groundwater | – |
– |
17.4 Leakage to landscape | 19 |
19 |
17.5 Overbank flood spilling | – |
– |
Total surface water decreases | 4,132,058 |
8,950,096 |
Water liability increases | ||
21 Surface water liability increases | ||
21.1 Surface water allocation announcements | 38,205 |
36,802 |
21.2 Surface water allocation announcements – urban water system | 775 |
775 |
21.3 Surface water allocation announcements – irrigation scheme | 338,100 |
338,100 |
Total surface water liability increases | 377,080 |
375,677 |
Balancing item—surface water | 596,553 |
2,799,023 |
Change in net water assets | (2,166,090) |
(4,375,152) |
Water inflows | 2012–13 volume (ML) |
2011–12 volume (ML) |
9 Surface water inflows | ||
9.1 Precipitation on surface water | 556,514 |
756,582 |
9.3 Groundwater discharge | – |
– |
9.4 Runoff to surface water | 2,171,758 |
6,794,954 |
9.5 Point return from irrigation scheme | – |
– |
9.6 Overbank flood return to river channel | – |
– |
9.9 Discharge from urban water system | 603 |
686 |
Total surface water inflows | 2,728,875 |
7,552,222 |
Water outflows | ||
17 Surface water outflows | ||
17.1 Evaporation from surface water | 1,488,640 |
1,663,087 |
17.2 River outflow from the region | 2,643,399 |
7,286,990 |
17.3 Leakage to groundwater | – |
– |
17.4 Leakage to landscape | 19 |
19 |
17.5 Overbank flood spilling | – |
– |
17.11 Entitled diversion of allocated surface water to users | 27,298 |
20,029 |
17.12 Entitled diversion of allocated surface water to urban water system | 427 |
422 |
17.13 Entitled diversion of allocated surface water to irrigation scheme | 153,697 |
155,362 |
Total surface water outflows | 4,313,480 |
9,125,909 |
Balancing item—surface water | 596,553 |
2,799,023 |
Opening water storage | 10,775,781 |
15,148,491 |
Change in water storage | (2,181,158) |
(4,372,710) |
Closing water storage | 8,594,623 |
10,775,781 |
A schematic diagram representing all the inflows and outflows associated with the surface water store in the Ord region is provided in Figure 4. The numbers in brackets on the diagram refer to the line item numbers in Table 3.
Figure 4 Schematic diagram of water inflows and outflows for the surface water store within the Ord region during the 2012–13 year; line item numbers are provided in brackets
Table 3 shows that surface water storage decreased during the 2012–13 year by 2,181,158 ML (approximately 20%). The decrease in surface water storage during the year is attributed to the decreased inflows into Lake Argyle during the 2012–13 year. This is reflected by the runoff to surface water (line item 9.4 Runoff to surface water), which was less than one-third of that during the comparison year (Table 3). The decrease in runoff reflects the below average rainfall conditions experienced across the region during the year (see Climate overview).
Figure 5 shows that most of the allocation diversion from surface water is for irrigation scheme water supply (line item 17.13 Entitled diversion of allocated surface water to irrigation scheme). During the 2012–13 year, irrigation scheme water supply made up approximately 85% of the total allocation diversion, a marginal decrease from the previous year (which was 88% of the total allocation diversion).
Figure 5 shows that allocation diversions from surface water during the 2012–13 year to individual users (line item 17.11 Entitled diversion of allocated surface water to users) have increased by approximately 36% from last year.
Figure 5 Graph of allocation diversions from surface water within the Ord region during the 2012–13 year and the 2011–12 comparison year; line item numbers are given in brackets
These allocation diversions are all associated with a water access entitlement. When an allocation is announced, a present obligation (water liability) is created on the surface water to deliver water to the users. As there is no carry-over provision in the region, the portion of the announced allocations that are not diverted by the end of the licence water year is forfeited.
The entitlement, allocation announcement, and forfeiture for each of these water rights during the 2012–13 year are provided in the Surface water rights section of the 'Water access and use' note.
The balancing item volume represents the difference between the measured opening and closing balances of the surface water store, after physical inflows and outflows have been applied. This item is an indication of both the accuracy of the volumes reported and the degree to which the reported water flows represents a complete surface water store balance.
The balancing item is calculated according to Table 4.
|
Account |
Volume (ML) |
|
Opening balance (1 July 2012) |
10,775,781 |
add |
Total surface water inflows (see Table 3) |
2,728,875 |
less |
Total surface water outflows (see Table 3) |
4,313,480 |
less |
Closing balance (30 June 2013) |
8,594,623 |
|
Balancing item—surface water store |
596,553 |
The calculation of the water balance on the surface water store yielded a balancing item of 596,553 ML. This is approximately 7% of the total surface water store volume at the end of the 2012–13 year and approximately 22% of the total surface water inflows during the 2012–13 year.
It is likely that the balancing item is primarily attributed to uncertainties associated with the runoff (a large source of surface water increase, line item 9.4 Runoff to surface water), river outflow from the region (a large source of surface water decrease, line item 17.2 River outflow from the region) and the lack of an estimate of surface water discharge to groundwater.
The runoff volume is derived from a rainfall–runoff model and it is reasonable to expect a 10–20% uncertainty around the estimated runoff volume (+/– 430,000 ML). The river outflow to sea is based on measured flow data collected at the most downstream station along a river. There is no adjustment made for the contributing area below the gauging station. As such, outflow to sea is likely to be underestimated by 10–20% (530,000 ML).
Groundwater
A description of the Ord region's groundwater resources is provided in the Groundwater section of the 'Contextual information'.
The aquifers in the Ord region are described in the Groundwater section of the 'Contextual information'. While some information exists on water movement to and from the aquifers (see following section on 'Changes in water store'), no value is available for the volume of water stored in the aquifers as indicated by dashes ('–') in Table 5. Further information is provided in line item notes 2.1 Water table aquifer and 2.2 Underlying aquifers.
The Statement of Water Assets and Water Liabilities for the groundwater store is shown in Table 5.
Water assets | Volume at 30 June 2013 (ML) |
Volume at 30 June 2012 (ML) |
2 Groundwater | ||
2.1 Water table aquifer | – |
– |
2.2 Underlying aquifers | – |
– |
Total groundwater assets | – |
– |
Water liabilities | ||
6 Groundwater liability | ||
6.1 Groundwater allocation remaining | 1,315 |
1,320 |
6.2 Groundwater allocation remaining – urban water system | 2,252 |
2,252 |
Total groundwater liabilities | 3,567 |
3,572 |
Opening net water assets | (3,572) |
(3,538) |
Change in net water assets | 5 |
(34) |
Closing net water assets | (3,567) |
(3,572) |
The only water movement to and from aquifers in the Ord region that can be quantified are the entitled abstractions for individual users and urban supply. It is assumed that aquifer recharge from the landscape (line item 10.3 Recharge from landscape) is equal to these abstractions.
Groundwater movement across the region boundary as well as surface water-groundwater interactions are considered to occur within the region; however, these flows could not be quantified, as indicated by dashes ('–') in tables 6 and 7.
The Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows for the groundwater store are provided in tables 6 and 7 respectively.
Water asset increases | 2012–13 volume (ML) |
2011–12 volume (ML) |
10 Groundwater increases | ||
10.1 Groundwater inflow from outside region | – |
– |
10.3 Recharge from landscape | 10,764 |
13,108 |
10.4 Recharge from surface water | – |
– |
Total groundwater increases | 10,764 |
13,108 |
Water liability decreases | ||
14 Groundwater liability decreases | ||
14.1 Adjustment and forfeiture of groundwater allocation | 2,467 |
85 |
14.2 Adjustment and forfeiture of groundwater allocation – urban water system | 954 |
898 |
Total groundwater liability decreases | 3,421 |
983 |
Water asset decreases | ||
18 Groundwater decreases | ||
18.1 Groundwater outflow to outside region | – |
– |
18.3 Discharge to landscape | – |
– |
18.4 Discharge to surface water | – |
– |
Total groundwater decreases | – |
– |
Water liability increases | ||
22 Groundwater liability increases | ||
22.1 Groundwater allocation announcements | 11,480 |
11,425 |
22.2 Groundwater allocation announcements – urban water system | 2,700 |
2,700 |
Total groundwater liability increases | 14,180 |
14,125 |
Balancing item—groundwater | 0 |
0 |
Change in net water assets | 5 |
(34) |
Water inflows | 2012–13 volume (ML) |
2011–12 volume (ML) |
10 Groundwater inflows | ||
10.1 Groundwater inflow from outside region | – |
– |
10.3 Recharge from landscape | 10,764 |
13,108 |
10.4 Recharge from surface water | – |
– |
Total groundwater inflows | 10,764 |
13,108 |
Water outflows | ||
18 Groundwater outflows | ||
18.1 Groundwater outflow to outside region | – |
– |
18.3 Discharge to landscape | – |
– |
18.4 Discharge to surface water | – |
– |
18.11 Entitled extraction of allocated groundwater to users | 9,018 |
11,266 |
18.12 Entitled extraction of allocated groundwater to urban water system | 1,746 |
1,842 |
Total groundwater outflows | 10,764 |
13,108 |
Balancing item—groundwater | 0 |
0 |
Opening water storage | – |
– |
Change in water storage | 0 |
0 |
Closing water storage | – |
– |
A schematic diagram representing all the inflows and outflows associated with the groundwater store in the Ord region is provided in Figure 6. The numbers in brackets on the diagram refer to the line item numbers in Table 7.
Figure 6 Schematic diagram of water inflows and outflows for the groundwater store within the Ord region during the 2012–13 year; line item numbers are provided in brackets
Allocations and extractions
Most of the extractions from the groundwater store are for licensed private use (line item 18.11 Entitled extraction of allocated groundwater to users), which accounts for approximately 84% of the total groundwater extraction. The majority of the allocated private water extractions are for mining use (see line item 22.1 Groundwater allocation announcements).
Figure 7 shows that allocation extractions from aquifers during the 2012–13 year for private use have decreased by approximately 20% from last year (see the Groundwater rights section of the 'Water access and use' note for more information). Extractions for urban water supply are similar to the 2011–12 year.
Figure 7 Graph of extractions from aquifers within the Ord region during the 2012–13 year and the 2011–12 comparison year; line item numbers are given in brackets
These allocation extractions are all associated with a water access entitlement. When an allocation is announced, an obligation (water liability) is created on the groundwater to deliver water to the users. As there is no carry-over provision in the region, the portion of the announced allocations that are not diverted by the end of the licence water year is forfeited.
The entitlement, allocation announcement, and forfeiture for each of these water rights during the 2012–13 year are provided in the Groundwater rights section of the 'Water access and use' note.
Balancing item
As shown in Table 7, the only groundwater outflows that can be quantified are the entitled abstractions for individual users and urban supply. It is assumed that the total groundwater inflow (line item 10.3 Recharge from landscape) is equal to these abstractions, so the groundwater store is assumed to balance (i.e., the balancing item is zero).