Ord
Supporting information
Introduction
The following set of notes provides consolidated reports for each of the water stores and systems within the Ord region during the 2013–14 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 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.
Figure 2 Between-store flows that occur within the Ord region
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 store
Surface water assets
The volume of the surface water assets include water held in storages (10,930,057 ML) and regulated rivers (14,800 ML). The regulated river is defined as the lower Ord River, which extends 76 km from Lake Kununurra (Figure 3) to the upper tidal limit.
The volume of water in unregulated rivers and 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 2013–14 year is shown in Figure 3.
Figure 3 Percentage-full volume on 30 June 2014 for each storage
Total volume of water within each storage at 30 June 2014, and at the end of the previous three years (2012, 2011 and 2010) is given in Figure 4.
Figure 4 Total volume of water in each storage within the Ord region at 30 June 2014, 2013, 2012 and 2011
The water volume in Lake Argyle increased during the 2013–14 year from 78% to 100% full at 30 June 2014. The capacity volume at the end of the 2013–14 year is attributed to the significant water event that occurred early February 2014 over the lower Ord region (see Water overview). This volume is still much lower than that observed on 30 June 2011 when Lake Argyle was 139% full due to record rainfall conditions observed during the 2010–11 year.
All other storages within the Ord region were more than 90% of capacity at 30 June 2014 (Figure 4). These smaller storage volumes remain relatively unchanged from year to year compared to Lake Argyle.
Surface water liabilities
Surface water liabilities in the Ord region refer to the volume of surface water allocation remaining on licence entitlements at the end of the 2013–14 year for:
- individual users (22,160 ML)
- urban water system (670 ML)
- irrigation scheme (270,944 ML).
Most of the water supply licences for the region do not have a water management year that ends on 30 June. Therefore, the volume of allocation remaining at the end of the 2013–14 year for the Ord region is the unused component of the annual allocation for these licence entitlements.
The allocation remaining for each licence entitlement is provided in tables 1–3.
| Account: individual users | Volume (ML) |
| Opening balance at 1 July 2013 | 20,262 |
| Surface water allocation announcements | 37,581 |
| Entitled diversion of allocated surface water to individual users | (26,271) |
| Adjustment and forfeiture of surface water allocation | (9,412) |
| Closing balance at 30 June 2014 | 22,160 |
| Account: urban water system | Volume (ML) |
| Opening balance at 1 July 2013 | 670 |
| Surface water allocation announcements | 775 |
| Entitled diversion of allocated surface water to urban water system | (473) |
| Adjustment and forfeiture of surface water allocation | (302) |
| Closing balance at 30 June 2014 | 670 |
| Account: irrigation scheme | Volume (ML) |
| Opening balance at 1 July 2013 | 270,673 |
| Surface water allocation announcements | 338,100 |
| Entitled diversion of allocated surface water to irrigation scheme | (146,094) |
| Adjustment and forfeiture of surface water allocation | (191,735) |
| Closing balance at 30 June 2014 | 270,944 |
Surface water inflows and outflows
A schematic diagram representing all the inflows and outflows associated with the surface water store in the Ord region is provided in Figure 5.
Figure 5 Water inflows and outflows for the surface water store within the Ord region during the 2013–14 year
Surface water inflows
The largest water inflow is runoff to surface water (13,915,118 ML). The volume of runoff during the 2013–14 year is approximately six times that during the previous year. This reflects the above average rainfall conditions experienced across the region during the year, particularly during the typically wettest months of January–February (see Climate overview). This is typical of catchments in northern Australia: periods of intense rainfall during the middle of the wet season, when the soil is likely to be under saturated conditions from early wet season rainfall, will have a relatively large impact on the runoff in the region.
The remaining two surface water inflows are precipitation on surface water (1,043,170 ML) and discharge from the urban water system (586 ML). More than 95% of the total volume of precipitation on surface water in the region occurs at Lake Argyle. The discharge from the urban system refers to the outflow of treated wastewater to rivers from treatment plants at Kununurra (528 ML) and Wyndham (58 ML).
The volume of return flow from the Ord River Irrigation Area to the Ord River cannot be quantified due to a lack of available data; however, based on recent data these return flows can range between 25,000 ML and 55,000 ML. Groundwater discharge (– ML) to surface water was also not recognised as it could not be adequately quantified. An expansion of the monitoring bore network and improved understanding of aquifer extent and properties are required to adequately quantify surface water-groundwater movement in the region.
Surface water outflows
The largest water outflow is the river outflow from the region (8,848,449 ML), which refers to the annual volume of flow from the Ord River to the Cambridge Gulf, and the Keep River to the Timor Sea during the 2013–14 year. This outflow is more than three times larger than that which occurred during the previous year, which primarily reflects the above average flow conditions in the lower Ord and Keep rivers compared to the very low flows experienced during the 2012–13 year (see Water overview).
Evaporation from surface water during the 2013–14 year was 1,384,330 ML. More than 95% of the total volume of evaporation from surface water in the region occurs at Lake Argyle. Total evaporation during the 2013–14 year is slightly lower than that which occurred during the previous year, which may be attributed to the increased rainfall (and hence cloud cover) that occurred during the year (see Climate overview).
The total annual leakage from surface water storages within the Ord region during the 2013–14 year was 45 ML. Groundwater recharge (– ML) from surface water was not recognised as it could not be adequately quantified.
Entitled water abstractions from the surface water store are described in Surface water allocation diversions below.
Surface water allocation diversions
Most of the entitled diversion of allocated surface water in the Ord region is for irrigation scheme water supply. During the 2013–14 year, 146,094 ML of surface water was diverted from the main Ord River channel to the Ord River Irrigation Area, which accounts for more than 84% of the total allocation diversion. The volume includes water diversions to the:
- Ivanhoe and Packsaddle irrigation districts for the Ord Irrigation Cooperative
- M1 channel for supply to Water Corporation customers (pumpers and siphon users), as well as for the flushing of ponding effluent from the channel (Figure 6).
Figure 6 Water allocations and abstractions to the Ord River Irrigation Area during the 2013–14 year
Entitled diversion of allocated surface water for individual users during the 2013–14 year was 26,271 ML, which accounts for approximately 15% of the total allocation diversion. Licences primarily relate to water sourced from the main Ord River channel, upper Ord River, Dunham River, and King River for the agricultural and mining sectors (see Surface water allocation announcements below).
Entitled diversion of allocated surface water for urban water supply during the 2013–14 year was 473 ML, which accounts for less than 1% of the total allocation diversion. This volume includes town supply for Wyndham and Lake Argyle Village (Figure 7).
Figure 7 Surface water allocations and abstractions to the urban water system for each town during the 2013–14 year
Surface water forfeitures
The portion of surface water allocation that has not been abstracted at the end of the water year is forfeited, that is, there is no carry-over of entitlements into the next water year. Water forfeitures in the Ord region during the 2013–14 year relate to licence entitlements for:
- individual users (9,412 ML)
- urban water system (302 ML)
- irrigation scheme (191,735 ML).
Surface water allocation announcements
Surface water allocation announcements in the Ord region during the 2013–14 year refer to surface water supply to:
- individual users (37,581 ML)
- urban water system (775 ML)
- irrigation scheme (338,100 ML).
There are approximately 100 individual users in the region that primarily source water from the main Ord River channel, upper Ord River, Dunham River and King River for agricultural and mining purposes. The water supply licences are divided into licence entitlement purposes. Figure 8 shows the annual allocation announcement to individual users for each licence purpose for the 2013–14 year.
Figure 8 Surface water allocation announcement to individual users for each licence purpose for the 2013–14 year
The urban water supply licences relate to town supply for Wyndham and Lake Argyle Village. The irrigation scheme licences relate to the Ord River Irrigation Area. The annual allocation for each irrigation and urban licence during the 2013–14 year is shown in Figure 6 and Figure 7 respectively.
A more detailed description of surface water allocations and associated water rights in the Ord region is given in the Surface water rights note.
Surface water balancing item
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: surface water store | Volume (ML) |
| Opening balance (1 July 2013) | 8,594,623 |
| Total surface water inflows | 14,958,874 |
| Total surface water outflows | (10,405,662) |
| Closing balance (30 June 2014) | (10,944,857) |
| Balancing item | 2,202,978 |
The calculation of the water balance on the surface water store yielded a balancing item of 2,202,978 ML. This is approximately 20% of the total surface water store volume at the end of the 2013–14 year and approximately 15% of the total surface water inflows during the 2013–14 year.
It is likely that the balancing item is primarily attributed to uncertainties associated with the runoff to surface water (a large source of surface water increase), river outflow from the region (a large source of surface water decrease) 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 (+/– 2,700,000 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% (1,700,000 ML).
Groundwater store
Groundwater assets
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 Groundwater inflows and outflows below), no value is available for the volume of water stored in the aquifers as indicated by dashes ('–') in the water accounting statements.
Groundwater liabilities
Groundwater liabilities in the Ord region refer to the volume of groundwater allocation remaining on licence entitlements at the end of the 2013–14 year for:
- individual users (1,222 ML)
- urban water system (2,252 ML).
Most of the water supply licences for the region do not have a water management year that ends on 30 June. Therefore, the volume of allocation remaining at the end of the 2013–14 year for the Ord region is the unused component of the annual allocation for these licence entitlements.
The allocation remaining for each licence entitlement is provided in tables 5 and 6.
| Account: individual users | Volume (ML) |
| Opening balance at 1 July 2013 | 1,315 |
| Groundwater allocation announcements | 11,312 |
| Entitled extraction of allocated groundwater to individual users | (8,965) |
| Adjustment and forfeiture of groundwater allocation | (2,440) |
| Closing balance at 30 June 2014 | 1,222 |
| Account: urban water system | Volume (ML) |
| Opening balance at 1 July 2013 | 2,252 |
| Groundwater allocation announcements | 2,700 |
| Entitled extraction of allocated groundwater to urban water system | (1,718) |
| Adjustment and forfeiture of groundwater allocation | (982) |
| Closing balance at 30 June 2014 | 2,252 |
Groundwater inflows and outflows
A schematic diagram representing all the inflows and outflows associated with the groundwater store in the Ord region is provided in Figure 9.
Figure 9 Water inflows and outflows for the groundwater store within the Ord region during the 2013–14 year
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 (see Groundwater allocation extractions below). It is estimated that aquifer recharge from the landscape (10,683 ML) is equal to these abstractions, which is based on the assumption that the volume of extraction in the long term leads to no change in aquifer levels.
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 Figure 9. An expansion of the monitoring bore network and improved understanding of aquifer extent and properties are required to adequately quantify groundwater movement in the region.
Groundwater allocation extractions
Most of the entitled extraction of allocated groundwater store in the Ord region is for individual use. During the 2013–14 year, 8,965 ML of groundwater was taken by individual users, which accounts for approximately 84% of the total allocated groundwater extraction. Licences primarily relate to water sourced from the Canning–Kimberley groundwater area for mining purposes (see Groundwater allocation announcements below).
Total groundwater extracted for urban water supply during the 2013–14 year was 1,718 ML, which accounts for approximately 16% of the total allocated groundwater extraction. This volume includes town supply for Kununurra and Halls Creek (Figure 10).
Figure 10 Groundwater allocations and abstractions to the urban water system for each town during the 2013–14 year
Groundwater forfeitures
The portion of groundwater allocation that has not been abstracted at the end of the water year is forfeited, that is, there is no carry-over of entitlements into the next water year. Water forfeitures in the Ord region during the 2013–14 year relate to licence entitlements for:
- individual users (2,440 ML)
- urban water system (982 ML).
Groundwater allocation announcements
Groundwater allocation announcements in the Ord region during the 2013–14 year refer to groundwater supply to:
- individual users (11,312 ML)
- urban water system (2,700 ML).
There are approximately 40 individual users in the region that primarily source water from the Canning–Kimberley groundwater area for the mining and commercial sectors. The water supply licences are divided into licence entitlement purposes. Figure 11 shows the annual allocation announcement to individual users for each licence purpose for the 2013–14 year.
Figure 11 Groundwater allocation announcement to individual users for each licence purpose for the 2013–14 year
The urban water supply licences relate to town supply for Kununurra and Halls Creek. The annual allocation for each urban licence during the 2013–14 year is shown in Figure 10 above.
A more detailed description of groundwater allocations and associated water rights in the Ord region is given in the Groundwater rights note.
Groundwater balancing item
As shown above, 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 (recharge from landscape) is equal to these abstractions, so the groundwater store is assumed to balance (i.e., the balancing item is zero).
Unaccounted-for difference
The volume recognised in the water accounting statements (2,202,978 ML) represents the total unaccounted-for difference for the Ord region for the 2013–14 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 7.
| Account: water storage | Volume (ML) |
| Opening water storage balance (1 July 2013) | 8,594,623 |
| Total water inflows | 14,969,557 |
| Total water outflows | (10,416,345) |
| Closing water storage balance (30 June 2014) | (10,944,857) |
| Unaccounted-for difference | 2,202,978 |
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 8.
| Balancing item | Volume (ML) |
| surface water store | 2,202,978 |
| groundwater store | 0 |
| Unaccounted-for difference | 2,202,978 |
The unaccounted–for difference volume is entirely attributed to the balancing item of the surface water store. Details regarding the balancing item's calculation are given in the Surface water store note.
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 0 ML.