Ord: Climate and water

  • Total annual rainfall was below average, with the region receiving 90% of its annual average rainfall.
  • Streamflows were below average for most of the year.
  • Soil moisture in the root zone (0–1 m depth) was average.

Schematic representation of the Ord region. In 2021–22, rainfall was 618 mm, below average with the region receiving 90% of its annual average rainfall. Streamflow in lower Ord River in 2021–22 was 2,782 GL compared to the average value of 6,034 GL. Soil moisture was average.

For further information on the region's climate and water conditions during the 2021-22 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 2021-22 year

  • Total area-averaged rainfall for the 2021–22 year was 618 mm, 10% below the mean value of 685 mm.
  • A negative Indian Ocean Dipole (IOD) was active between July and December and there was a La Niña event between November and April - both drivers typically increase rainfall across the region.
  • From July to October, rainfall was fairly low across the region but close to average for this time of year.
  • There were only four main active monsoon events during the wet season (early-November 2021, late-December 2021, mid-January 2022, and late-April 2022) with ex-tropical cyclone Tiffany contributing to January's above average rainfall.
  • Low monsoonal activity was the key factor in wet season rainfall being below average.
  • June was wetter than usual due to a low pressure system bringing unseasonal showers. 
  • More information on Australia's climate and water over the 2021-22 year can be found at: Financial year climate and water statement 2021-22.

 

Figure C2 Total monthly rainfall for the Ord region during the 2021-22 year compared with the average and percentiles for the region

  • Dry season rainfall (July to October 2021) was close to average.
  • Ex-tropical cyclone Tiffany and a monsoon trough resulted in January rainfall being 54% above the monthly average, but less than the 90th percentile.
  • All months ranked within the 10th and 90th percentiles for each respective month.

 

Actual evapotranspiration

Figure C3 Annual and monthly actual evapotranspiration deciles for the Ord region during the 2021-22 year

  • Total area-averaged actual evapotranspiration was close to average across the region during the 2021-22 year.
  • Evapotranspiration was average to above average in the months leading up to the 2021-22 wet season (July to October) and particularly high during November.
  • While evapotranspiration was still high in February due to significant January rains, low February to April rainfall and the consequent reduction in water availability resulted in lower evapotranspiration over the March to May period.

 

Soil moisture

Figure C4 Annual and monthly soil moisture deciles for the Ord region during the 2021-22 year

  • Soil moisture in the root zone (0–1 m depth) was close to average across the region for the 2021-22 year.
  • Soil moisture was average to below average by the start of the wet season.
  • Following significant rainfall events, soil moisture was above average in November and again in January to February 2022.
  • Without further significant wet season rainfall, root soil was relatively dry from March onwards.
  • More information on soil moisture distribution across the Ord region is available in the Australian Water Outlook.

 

Streamflow responses

Map of key gauging stations. In the southeast upstream of Lake Argyle are Ord River at Old Ord Homestead, station number 809316, and Negri River at Mistake Creek Homestead, station number 809315. Ord River at Tarrara Bar, station number 809339, is downstream of Lake Argyle in the north.
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 the dam spilling.

 

Figure C6 Total monthly flow for major rivers in the Ord region during the 2021-22 year compared with the average and percentiles

  • Total annual flows recorded at all three gauges (Negri River, Upper Ord River, and Lower Ord River) were below average during the 2021-22 year.
  • For example, total annual flow in the Ord River at Old Ord Homestead (Station 809316) was 1,201 GL, around two thirds of the annual average of 1,797 GL.
  • Streamflows peaked in January at all sites following heavy rainfall across the region - this was the only wet season event to significantly increased flows.
  • The lack of monsoonal activity for the remainder of the 2021-22 wet season returned flows to well below average levels.

 

Major water reforms

Ord–East Kimberley Expansion Project

  • The Ord–East Kimberley Expansion Project is a major initiative of the Western Australian Government.
  • The first stage of the expansion developed 74 km of irrigated farmland in the Goomig Farmlands. The portion of irrigated land in the Goomig Farmlands has been increasing each year since the first planting of crops commenced in 2015.
  • The project is continuing to build on the $517 million Ord-East Kimberly Expansion Project.
  • The projects aim is to double the size of the Ord Irrigatino Scheme Area to 29,000ha.
  • Further information on the Ord–East Kimberley Expansion Project can be found on the Western Australian Government's Department of Primary Industries and Regional Development website.