Significant water events
The Ord region experienced high flows during the 2010–11 year as a result of cool and wet conditions.
Water allocations in the region were not affected, as the annual water entitlements are only at 41% of the entitlement limit, and there is enough surplus water stored in Lake Argyle to administer entitlements and flow release obligations.
The effect of wet conditions on runoff and storage levels was that the volume of water in storage increased by 71% from the start of the reporting period.
The upper Ord River and Negri River contribute most of the inflows to Lake Argyle. Flows in these rivers were above average during the 2010–11 year.
Wet season flow (February to April) was generally well above the 50th percentile for the catchments and above 90th percentile in March and April. Total annual flow in the upstream reach of Ord River was 8,765 GL, well above the mean annual flow of 2,038 GL. Monthly flows were generally high relative to historical monthly deciles (Figure W1). Total annual flow in the nearby Negri River was 2,099 GL, well above the mean annual flow of 545 GL. Again, monthly flows were generally high relative to historical 10th, 50th and 90th percentiles (Figure W2).
Figure W1. Total monthly flow along upper Ord River during the 2010–11 year compared with long-term percentiles
Figure W2. Total monthly flow along Negri River during the 2010–11 year compared with long-term percentiles
Total annual flow during the 2010–11 year in the lower Ord River was 15,693 GL, compared with the mean annual flow of 7,335 GL. Monthly flow observations were generally high compared with historical 10th, 50th and 90th percentiles, especially for April and May, noting that these percentiles are derived from a relatively short period of record (Figure W3).
Figure W3. Total monthly flow along Lower Ord River during the 2010–11 year compared with long-term percentiles
Figure W4 shows the location of the gauging stations used as the source of data for figures W1 to W3. Stations on the upper Ord and Negri rivers are located upstream of Lake Argyle. The Negri River is a tributary of the upper Ord. The Negri River gauging station lies within the Northern Territory. The lower Ord River gauging station is located downstream of both Lake Argyle and Lake Kununurra.
Figure W4. Map of the location of gauging stations used for flow graphs in figures W1 to W3
Major water initiatives
The Ord–East Kimberley Expansion project is a major initiative of the Western Australian Government. The State committed $220 million from the Royalties for Regions fund under the Ord Irrigation Expansion Project and a further $195 million was contributed by the Australian Government via the East Kimberley Development Package.
The initiative will develop 80 km² of land for irrigation on the Weaber Plain in the Keep River catchment over the next two years, subject to environmental approval from the Australian Government. Infrastructure planned includes irrigation distribution canals, drainage and roads. The development will increase the irrigated land by 50%. Expressions of interest and requests for proposals have closed for around 7,400 hectares of subdivided irrigable land in the Goomig Farm Area, 6,000 hectares in Knox Plain and 1,700 hectares in the Ord West Bank. A further 80 km² of irrigation land is planned to be developed in the Keep River by 2013.
The total potential area for irrigation expansion is shown in Figure W5.
Figure W5. Map of Ord River Irrigation Area expansion