Ord: Climate and water
Several tropical low pressure systems over northwestern Australia contributed to well above-average annual rainfall in the region, particularly during January–February, the typically wetter months of the year. The high rainfall during this period contributed to well above-average streamflows across the region.
For further information on the region's climate and water conditions during the 2016–17 year scroll down this page or click on the links below:
About the region
The Ord region lies within the wet–dry tropics of northern Australia, which has a distinct and predictable climatic seasonality. Almost all rainfall in the region occurs during the wet season (November–April). As a consequence, flow in the rivers is strongly seasonal. Many of the region's rivers, including those that flow into Lake Argyle, cease to flow during the dry season (May–October).
Climate conditions
Rainfall
Figure C1 Annual and monthly rainfall deciles for the Ord region during the 2016–17 year
- Several tropical low pressure systems over northwestern Australia during January–February, typically the wetter months of the year, contributed to the third highest annual rainfall recorded across the region.
- Total area-averaged rainfall for the year was 1,269 mm, almost double the mean annual rainfall of 658 mm.
Figure C2 Total monthly rainfall for the Ord region during the 2016–17 year compared with the long-term average and percentiles for the region
- Rainfall was above average for almost the entire wet season (November–April).
- January rainfall was almost three times the average for the month; some parts of the region recorded their highest January rainfall on record.
Actual evapotranspiration
Figure C3 Annual and monthly actual evapotranspiration deciles for the Ord region during the 2016–17 year
- Total area-averaged actual evapotranspiration was 722 mm, higher than the mean value of 532 mm.
- The above-average evapotranspiration may be attributed to a combination of above-average temperatures across the region and increased water availability due to the high rainfall during the year.
Figure C4 Total monthly actual evapotranspiration for the Ord region during the 2016–17 year compared with the long-term average and percentiles for the region
- Actual evapotranspiration was above average for almost the entire year.
Soil moisture
Figure C5 Annual and monthly soil moisture deciles for the Ord region during the 2016–17 year
- Soil moisture in the root zone (0–1 m depth) was above average across the entire region.
- Rainfall and soil moisture are typically closely aligned. For example, above-average soil moisture during January–March 2017 reflects the above-average rainfall that occurred during the typically wetter months of the year (January–February).
- More information on soil moisture distribution across the Ord region is available in the Australian Landscape Water Balance.
Streamflow responses
Streamflow
Figure C6 Key flow gauging stations along the main rivers within the Ord region
- The upper Ord and Negri rivers are two primary rivers that flow into Lake Argyle.
- Streamflow in the lower Ord River below Lake Argyle is influenced by hydropower releases, diversions for consumptive use, dam operations, and dam spilling.
Figure C6 Total monthly flow for major rivers in the Ord region during the 2016–17 year compared with long-term average and percentiles
- Total annual flows in the upper Ord and Negri rivers were more than twice the mean annual flow, and more than 8 times larger than the previous year.
- Total annual flow in the lower Ord River was more than 75% greater than the mean annual flow.
- The combination of above-average rainfall and soil moisture conditions experienced during the typically wetter months of the year (January–February) resulted in well above-average streamflows during this 2-month period.
- Above-average flow in the lower Ord River during the latter part of the year (April–June) was due to continued spilling from Lake Argyle, which remained above 100% capacity during this period.
Major water reforms
Ord–East Kimberley Expansion Project
Figure C10 Proposed expansion in the Ord River Irrigation Area
- The Ord–East Kimberley Expansion Project is a major initiative of the Western Australian Government.
- The first stage of the expansion will develop 74 km² of irrigated farmland in the Goomig Farmlands, with an option to develop a further 60 km² in the Knox Creek Plain area. During the 2016–17 year, approximately 5.5 km² of the Goomig Farmlands was cropped and irrigated.
- The Ord Irrigation Cooperative currently holds a licence for diversion of 335,000 ML/year for the Ivanhoe and Packsaddle plains. Kimberley Agricultural Investment Pty Ltd were issued a licence in mid-2015 for diversion of 47,000 ML/year for the Goomig Farmlands, which is expected to increase to the total commitment of 120,000 ML/year in the next few years.
- Additional water demand for the Knox Creek Plain area is expected to be 60,000–110,000 ML/year.
- Development of other proposed areas could take place in the next 5–10 years. Further details on these potential irrigation areas are given in Chapter 3 of the Ord Surface Water Allocation Plan.
- Further information on the Ord–East Kimberley Expansion Project can be found at the Department of Primary Industries and Regional Development and Office of Northern Australia websites.