Ord: Climate and water
- Rainfall was higher than average in November 2017 and January 2018; all other months had below-average rainfall.
- Less than average rainfall over the upper catchments of the Ord and Negri rivers resulted in low inflows into Lake Argyle during the year.
For further information on the region's climate and water conditions during the 2017–18 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. 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 2017–18 year
- Total area-averaged rainfall for the year was 609 mm, below the mean value of 658 mm.
- Above-average annual rainfall occurred over the coastal parts of the region; less rainfall occurred over the southern part of the region upstream of Lake Argyle.
- Two tropical lows over northern Australia during January 2018 contributed to above-average rainfall for that month across most of the region.
- Although it was one of the wetter years on record for the Kimberley region, much of the heavy rainfall occurred over the coastal areas across the western part of the Kimberley; less rainfall was experienced over the east Kimberley in the Ord region.
Figure C2 Total monthly rainfall for the Ord region during the 2017–18 year compared with the average and percentiles for the region
- Rainfall was above average in November 2017 and January 2018. All other months had below-average rainfall.
Actual evapotranspiration
Figure C3 Annual and monthly actual evapotranspiration deciles for the Ord region during the 2017–18 year
- Total area-averaged actual evapotranspiration was average to above average across the region.
- Above-average evapotranspiration during the dry season months (July–October 2017) was likely due to the continuation of increased water availability across the region following one of the wettest years on record in 2016–17 (see the 2017 Account).
- The above-average evapotranspiration that occurred during most of the wet season (November–April) may be due to a combination of above-average temperatures across the region and increased water availability following high rainfall in November 2017 and January 2018.
Soil moisture
Figure C4 Annual and monthly soil moisture deciles for the Ord region during the 2017–18 year
- Soil moisture in the root zone (0–1 m depth) was average across most of the region.
- Rainfall and soil moisture are typically closely aligned. For example, above-average soil moisture during the 4-month period from November–February is due to above-average rainfall that occurred during November 2017 and January 2018. The below-average soil moisture during March–June can be attributed to the relatively poor rainfall that occurred during the latter part of the wet season (February–April), particularly over the river catchments upstream of Lake Argyle.
- More information on soil moisture distribution across the Ord region is available in the Australian Landscape Water Balance.
Streamflow responses
Streamflow
Figure C5 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 2017–18 year compared with average and percentiles
- Total annual flows in the upper Ord and Negri rivers were less than 15% of the average annual flow.
- Flow in these rivers during January–February 2018 was less than expected given the high rainfall that occurred over the region in January. It's likely that most of the heavy rainfall associated with the tropical low that impacted the region in early January, which contributed to most of the January rainfall, occurred over the coastal parts of the region and less on the upper reaches of the Ord and Negri rivers.
- Flow in the lower Ord River was lower than usual during the typically higher flow months (February–May) due to the lack of large wet season flood events that occurred during the year.
Major water reforms
Ord–East Kimberley Expansion Project
Figure C7 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 2017–18 year, approximately 3.5 km² of cotton was planted in the Goomig Farmlands, the first cotton crop in the region since 2011.
- The Ord Irrigation Cooperative currently holds a licence for diversion of 246,300 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 planned 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.