National Water Account 2019

Ord: Climate and water

  • Total annual rainfall was below average and the lowest since the 1991–92 year.
  • The relatively poor rainfall during the wet season resulted in very low flows in the Ord River.
  • This was the second successive year of very low inflows into Lake Argyle.


For further information on the region's climate and water conditions during the 2018–19 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 2018–19 year

 

  • Total area-averaged rainfall for the year was 464 mm, well below the mean value of 659 mm.
  • The 2018–19 annual rainfall was the region's lowest since the 1991–92 year.
  • Annual rainfall was below average across almost the entire region. Large tropical low events that typically bring most of the rainfall to the region did not occur during the year.

 


Figure C2 Total monthly rainfall for the Ord region during the 2018–19 year compared with the average and percentiles for the region

 

  • Rainfall was marginally above average in November 2018. All other months had below-average rainfall.

 

Actual evapotranspiration

Figure C3 Annual and monthly actual evapotranspiration deciles for the Ord region during the 2018–19 year

 

  • Total area-averaged actual evapotranspiration was average to below average across the region.
  • The below-average evapotranspiration that occurred over most of the region towards the end of the wet season (March–April) reflects the decreased water availability following low wet season rainfall.

 

Soil moisture

Figure C4 Annual and monthly soil moisture deciles for the Ord region during the 2018–19 year

 

  • Soil moisture in the root zone (0–1 m depth) was below average across most of the region.
  • Rainfall and soil moisture are typically closely aligned. For example, the below-average soil moisture conditions across the entire region during March–April 2019 are due to the relatively poor wet season rainfall, particularly in March 2018.
  • The poor soil moisture conditions during the latter part of the 2018 dry season (July–September) can be attributed to the low rainfall that occurred during the latter part of the 2017–18 wet season (see the 2018 Account).
  • More information on soil moisture distribution across the Ord region is available in the Australian Landscape Water Balance.

 

Streamflow responses

Streamflow

Figure C5 Map of key flow gauging stations along the main rivers within the Ord region
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 2018–19 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. Streamflow in the Negri River was the lowest in almost 40 years.
  • This was the second successive year of very low inflows into Lake Argyle.
  • The above-average rainfall that occurred on the upper reaches of the Ord and Negri rivers in November 2018 had little effect on streamflow in these rivers due to the very poor soil moisture conditions across the region prior to the start of the 2018–19 wet season.
  • Total annual flow in the lower Ord River at Tarrara Bar (Station 809339) was 2,569 GL, well below the average value of 6,462 GL. Flow was particularly low during the typically higher flow months (February–May) due to the lack of large wet season flood events occurring during the year.

 

Major water reforms

Ord–East Kimberley Expansion Project

Figure C7 Map of proposed expansion in the Ord River Irrigation Area
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. The portion of irrigated land in the Goomig Farmlands has been increasing each year since the first planting of crops commenced in 2015.
  • 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 currently holds a licence for diversion of 32,000 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.