Significant water events
The upper Ord and Negri rivers contribute most of the inflows to Lake Argyle. Total annual flows in these rivers were below average during the 2011–12 year, and an order of magnitude below that recorded during the 2010–11 year.
Total annual flow during the 2011–12 year in the lower Ord River was only slightly below the mean annual flow.
Dry season flow (July–November) was almost entirely above the 90th percentile for the upper and lower Ord River and the Negri River (Figures W1–W3). Rainfall during this period was equivalent to average conditions. Therefore, these high flows are likely to be the receding discharge of the record high wet season flow observed during the 2010–11 year. Total flow during this 5-month period in the lower Ord River was higher than that observed during the typically much 'wetter' remainder of the year (December–June) (Figure W3).
During January and February, monthly flow in these rivers was well below the 50th percentile, which reflects the below average rainfall observed over the region during this period (see Figure C3 in Climate overview). The 3-month period between January and March is usually when the majority of the total annual flow occurs in these rivers. Therefore, the very low flows during January and February contributed to the overall below average annual flow during the 2011–12 year.
Average to above average flows were observed for the remainder of the wet season from March–June (Figures W1–W3).
Figure W1 Total monthly flow along upper Ord River during the 2011–12 year compared with long-term percentiles
Figure W2 Total monthly flow along Negri River during the 2011–12 year compared with long-term percentiles
Figure W3 Total monthly flow along lower Ord River during the 2011–12 year compared with long-term percentiles
Figure W4 shows the location of the gauging stations used as the source of data for figures W1–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 River. 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–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 for subdivided irrigable land in the Goomig Farm Area (7,400 hectares), Knox Plain (6,000 hectares) and Ord West Bank (1,700 hectares) have now closed. A further 80 km² of land is planned for irrigation development in the Keep River in 2013.
The total potential area for irrigation expansion is shown in Figure W5.
Figure W5 Map of Ord River Irrigation Area expansion
Further information on the Ord–East Kimberley Expansion Project can be found at the following Government of Western Australia websites: