Murray–Darling Basin: Climate and water
- Total annual rainfall was below average for the third consecutive year.
- Streamflows were very low in the latter half of 2019 reflecting the dry conditions.
- High rainfall in early 2020 resulted in some streamflow recovery.
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 Murray-Darling Basin region's climate ranges from sub-tropical in the north, to semi-arid in the west, and temperate in the south.
- Average rainfall across the region ranges from more than 2,100 mm in the highland areas in the southeast to less than 300 mm in the semi-arid areas in the west.
- Typically, streamflow in the northern part of the region reflects the sub-tropical rainfall distribution with higher streamflows in the late summer–early autumn months (January–March) following the higher summer rainfall period.
- Flow in the southern part of the region reflects the more temperate climate with higher flows in the late winter–early spring months (August–October) following winter rainfall.
Climate conditions
Rainfall
Figure C1 Annual and monthly rainfall deciles for the Murray–Darling Basin region during the 2019–20 year
- Total area-averaged rainfall for the year was 368 mm, less than the mean value of 464 mm. This was the region's third consecutive year of low rainfall.
- Rainfall was very low during the latter half of 2019. The below-average rainfall throughout July–December 2019 was influenced by a positive phase of the Indian Ocean Dipole, one of the strongest on record, as well as a negative phase of the Southern Annular Mode at the end of 2019 (see the Bureau's 2019–20 Climate Report for more information).
- The calendar year period between 2017–2019 has been the region's driest 36-month period on record (see the Bureau's Special Climate Statement for more information).
- There was some rainfall relief during the early part of 2020, particularly during February–April, as tropical moisture associated with warmer than average sea surface temperatures off the northwest coast of Australia moved across the continent and combined with southern cold fronts to produce high rainfall across the region.
- Below-average rainfall conditions returned in May–June 2020, which was influenced by a positive phase of the Southern Annular Mode during that period.
Figure C2 Total monthly rainfall for the Murray–Darling Basin region during the 2019–20 year compared with the average and percentiles for the region
- Rainfall during February–April 2020 was above average. All other months were below average.
- Rainfall in December 2019 was well below the 10th percentile. It was the region's second driest December on record and the driest in more than 80 years.
Actual evapotranspiration
Figure C3 Annual and monthly actual evapotranspiration deciles for the Murray–Darling Basin region during the 2019–20 year
- Total area-averaged actual evapotranspiration was below average across most of the region.
- The very low annual evapotranspiration reflects the dry conditions and low water availability throughout most of the year.
- Evapotranspiration was average over large parts of the region during February–April 2020 due to increased water availability following the higher rainfall during this 3-month period.
Soil moisture
Figure C4 Annual and monthly soil moisture deciles for the Murray–Darling Basin region during the 2019–20 year
- Soil moisture in the root zone (0–1 m depth) was average to below average across most of the region.
- In July 2019, root-zone soil moisture was already below average over most of the region following a very dry 2018–19 year. Continued dry conditions during the latter half of 2019 meant that by December 2019, root-zone soil moisture was well below average and lowest on record over inland areas of the region.
- Soil moisture was above average over large parts of the region in April 2020 following higher rainfall during the early part of 2020. The relatively poor rainfall during May–June 2020 meant that by June 2020 there were large areas of average to below-average soil moisture across the region.
- More information on soil moisture distribution across the Murray–Darling Basin region is available in the Australian Landscape Water Balance.
Streamflow responses
Figure C5 Key flow gauging stations along the main rivers within the Murray–Darling Basin region
- The Murray and Darling rivers are the two primary river systems within the region. Streamflow in the River Murray is influenced by dam operations and diversions for consumptive use.
- Most of the major tributaries of the Murray and Darling rivers in the southern part of the region represent predominantly regulated rivers; most of the major tributaries in the north represent unregulated rivers.
Figure C6 Total monthly flow for major rivers in the Murray–Darling Basin region during the 2019–20 year compared with the average and percentiles
- Streamflows were well below average for most of the year reflecting the dry conditions experienced across the region. For example, total annual flow in the River Murray at Lock 1 Downstream (Station A4260903) was 1,494 GL compared to the average value of 5,477 GL.
- Streamflow was particularly low during the latter half of 2019. By December 2019, most of the rivers had reached record low flows. Very few rivers across the northern part of the Basin were flowing at all.
- Above-average rainfall across large areas of New South Wales and Victoria in the early part of 2020, particularly during February to April, resulted in some recovery, with flows occurring in all the major rivers within the Murray–Darling Basin.
- Streamflow in the lower Darling River reconnected with the Murray River in mid-April 2020 for the first time since January 2018. In February 2020, major flows from the Lower Balonne River into the Ramsar-listed Narran Lakes wetland system occurred for the first time in eight years.
- More information on streamflow distribution across the Murray–Darling Basin region is available in the Regional water information.