National Water Account 2020

Ord: Climate and water

  • Total annual rainfall was below average for the third consecutive year.
  • The poor wet season rainfall resulted in very low flows in the Ord River.
  • This was the third consecutive year of very low inflows into Lake Argyle.


For further information on the region's climate and water conditions during the 2019–20 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 2019–20 year

 

  • Total area-averaged rainfall for the year was 557 mm, well below the mean value of 683 mm.
  • The transition of the Southwest Indian Monsoon into the southern hemisphere was six weeks later than average and the latest on record. The delayed monsoon period meant very little rainfall occurred across the region at the start of the 2019–20 wet season, which contributed to the below-average annual rainfall.
  • This was the region's second consecutive year of well below-average wet season rainfall. Over the last two years, the region has experienced its driest 24-month period since 1969–71.
  • Heavy rainfall associated with ex-tropical cyclone Esther, which crossed the region in late February 2020, contributed to above-average rainfall for that month.

 

Figure C2 Total monthly rainfall for the Ord region during the 2019–20 year compared with the average and percentiles for the region

 

  • Rainfall was above average in February and April 2020; all other wet season months (November–April) had well below-average rainfall.

 

Actual evapotranspiration

Figure C3 Annual and monthly actual evapotranspiration deciles for the Ord region during the 2019–20 year

 

  • Total area-averaged actual evapotranspiration was average to below average across the region.
  • Evapotranspiration was below average during July 2019–January 2020 due to low water availability across the region following a dry year in 2018–19 (see the 2019 Account) combined with the delayed onset of the 2019–20 monsoon period.
  • Evapotranspiration was above average over parts of the region during February–March 2020 following heavy rainfall associated with ex-tropical cyclone Esther, which crossed the region in late February 2020.

 

Soil moisture

Figure C4 Annual and monthly soil moisture deciles for the Ord region during the 2019–20 year

 

  • Soil moisture in the root zone (0–1 m depth) was average to below average across the region.
  • The delayed monsoon period meant very little rainfall occurred at the start of the 2019–20 wet season. By December 2019, root-zone soil moisture was below-average across almost the entire region.
  • Soil moisture was average to above average during February–March 2020 following heavy rainfall associated with ex-tropical cyclone Esther that crossed the region in February 2020.
  • 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 2019–20 year compared with average and percentiles

 

  • Total annual flows in the upper Ord and Negri rivers were well below average, particularly in the Negri River.
  • This was the third consecutive year of very low inflows into Lake Argyle.
  • Total annual flow in the lower Ord River at Tarrara Bar (Station 809339) was 3,151 GL, well below the average value of 6,312 GL.
  • The above-average rainfall that occurred over the region in February 2020 had little effect on streamflow in these rivers. The very dry conditions during the first half of the wet season following the delayed onset of the monsoon period meant that much of the rainfall that occurred was soaked up by the soil.

 

Major water reforms

Ord–East Kimberley Expansion Project

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 around 72,000 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.