Ord: Supporting information
- Below-average wet season rainfall contributed to low storage inflows and runoff across the region.
- End-of-year storage volume dropped to 40% full, the third consecutive annual drop in storage.
- 69% of the allocated water was taken in 2019–20, primarily for irrigated agriculture.
For further information on the region's water accounting statements scroll down this page or click on the links below:
Water assets
- Water asset volumes in the region at 30 June 2020 were 4,400 GL, more than 99% of which is water held in storages. The remaining amount is water held in rivers.
Figure S1 Total storage volume in the region at 30 June 2020 compared with the previous 10 years
- Storage volumes decreased from 54% full at 30 June 2019 to 40% full at 30 June 2020, the third consecutive annual drop in storage.
- Water in Lake Argyle makes up more than 98% of the region’s total surface water storage. Storage in Lake Argyle at 30 June 2020 was the lowest end-of-year storage volume in almost 30 years.
Figure S2 Percentage-full volume on 30 June 2020 for each storage and total daily storage volume from 2013–2020 (inset)
- For the third consecutive year, the normal filling and spilling of the storages did not occur due to below-average rainfall in the upper catchment areas during the wet season.
- Except for a small increase in storage during February–March 2020 following high rainfall associated with ex-tropical cyclone Esther that crossed the region in February, storage volumes declined for most of the year.
- In January 2020, storage volumes dropped to 38% full, the region's lowest level since early 1993.
- More detailed information on the individual storages within the region is available on the Bureau of Meteorology's Water Storage website.
Water liabilities
- Water liabilities in the Ord region refer to the volume of allocation remaining on licence entitlements at the end of the 2019–20 year.
| Description | Individual users (ML) | Urban system (ML) | Irrigation scheme (ML) | |
| Opening balance at 1 July 2019 | 10,128 | 670 | 233,074 | |
| add | Allocation | 37,998 | 700 | 411,954 |
| less | Allocated diversion | 28,208 | 425 | 280,105 |
| less | Adjustment and forfeiture | 9,790 | 275 | 74,229 |
| Closing balance at 30 June 2020 | 10,128 | 670 | 290,694 | |
| Description | Individual users (ML) | Urban system (ML) | |
| Opening balance at 1 July 2019 | 1,155 | 2,252 | |
| add | Allocation | 5,682 | 2,700 |
| less | Allocated extraction | 4,850 | 1,778 |
| less | Adjustment and forfeiture | 832 | 922 |
| Closing balance at 30 June 2020 | 1,155 | 2,252 | |
- 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 is the unused component of the annual allocation for these entitlements.
- A more detailed description of water allocations in the Ord region is given in the Water use section below.
Water flows
Figure S3 Water inflows and outflows for the surface water store during the 2019–20 year
Figure S4 Water inflows and outflows for the groundwater store during the 2019–20 year
- Total surface water flows into the region's storages was 2,860 GL. The key item contributing to surface water inflows was runoff, which made up 83% of the total surface water inflows for the region.
- For the third consecutive year, runoff was much lower than average (based on modelled data from 1971–2020) due to relatively poor wet season rainfall across the region.
- The key item contributing to surface water outflows from the region's storages was river outflow, which made up two thirds of the total surface water outflows. River outflow was below average due to the dry conditions and low runoff across the region.
- Water taken for consumptive use was 315 GL, around 5% of the total outflow (see Water use section below).
Water use
Figure S5 Surface water taken during the 2019–20 year in the region's key water management areas
Figure S6 Groundwater taken during the 2019–20 year in the region's key water management areas
- Total surface water diverted in the region was 308,738 ML.
- 91% of the total diversion was for irrigation scheme supply, all within the Main Ord River management area; 9% was for individual users and less than 1% was for the urban system.
- Total groundwater extracted was 6,628 ML.
- 73% of the total extraction was for individual users while 27% was for the urban system.
Figure S7 Surface water allocations and diversions in the Ord region for the years ending 30 June, from 2012–2020
- In 2019–20, total surface water allocation was 451 GL, mostly for irrigated agriculture in the Ord River Irrigation Area. 69% of the allocated surface water was taken.
- Water allocation for irrigation scheme supply was higher than the previous year due to the expansion of irrigation in the Goomig Farmlands (see Major water reforms).
- During the last two years, water taken for irrigation scheme supply has been much higher than previous years. The increase in irrigation scheme supply has been influenced by the very dry conditions across the region during the last two years, as well as the continued expansion of irrigation in the Goomig Farmlands.
- Surface water allocations and diversions for individual users and the urban system remained relatively unchanged. Town supply in particular changes little from year to year.
Figure S8 Groundwater allocations and extractions in the Ord region for the years ending 30 June, from 2012–2020
- In 2019–20, total groundwater allocation was 8 GL, mostly for mining purposes. 79% of the allocated groundwater was taken.
- Water allocations and extractions for individual users were similar to last year.
- The large decrease in allocations for individual users in 2017–18 was due mainly to an adjustment in water entitlement for the Argyle Diamond Mine, one of the larger groundwater licences in the region.
- Allocations and extractions for the urban system remained relatively unchanged. Town supply changes little from year to year.
Water market activity
- In 2019–20, one water entitlement trade of 2,400 ML occurred within the Main Ord River management area (see the Bureau's Water Markets Dashboard for more information).
- Information on water entitlement transactions that can occur in the region can be found on the Western Australia Department of Water and Environmental Regulation website.
Cultural and environmental water
Cultural benefit
- Periods of low flow in the lower Ord River are administered to support traditional hunting and fishing activities (see the Cultural water management section in the 'Region description'). This occurs when maintenance or inspection works on dam infrastructure is required.
- During the 2019–20 year there were no reductions in flow administered in the lower Ord River.
Environmental benefit
Environmental water provisions
- Environmental water provisions in the region are defined for the lower Ord River and include baseflow and wet season flood event requirements.
Figure S9 Example water provisions for the lower Ord River; required baseflows and wet season flood events are also shown
- The required flow regimes are maintained from a combination of water releases from Lake Argyle and Lake Kununurra, and unregulated catchment inflow.
- Larger, less frequent wet season flood events are also a component of the environmental water provisions, but are not shown on the figure above. These events occur as a result of runoff from the catchment downstream of Lake Argyle and cannot be managed by water releases from the storages.
- A more detailed description of the environmental water provisions for the lower Ord River is provided in Chapter 4 of the Ord Surface Water Allocation Plan.
Environmental water outcomes
Figure S10 Flow in the lower Ord River compared with the required flow regime during the 2019–20 year
- Flow in the lower Ord River exceeded the minimum baseflow requirements and most of the wet season peak flow requirements. Only at the peak threshold of 125 m3/s were the flow requirements not met (the level was exceeded during three spells rather than the required four).
- A larger flood peak in early March 2020 met the required 1 in 4-year flood event (average daily discharge >1,400 m3/s). A flood peak of this size had not occurred in the lower Ord River since February 2017.