Murray–Darling Basin: Climate and water
- Total annual rainfall was well below average and the lowest in 15 years.
- Some areas in the northern part of the region experienced their lowest annual rainfall on record.
- The relatively poor rainfall, particularly over the northern part of the region, resulted in very low flows in the Darling River.
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 Murray-Darling Basin region's climate ranges from sub-tropical in the north, to semi-arid in the west, to 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 2017–18 year
- Total area-averaged rainfall for the year was 337 mm, well below the mean value of 461 mm and the lowest in 15 years.
- The northern part of the region experienced relatively drier conditions compared to the southern part, with some areas in the north experiencing their lowest annual rainfall on record.
- Heavy rainfall associated with a low level trough and upper level low during October 2017 contributed to above-average rainfall for that month across the northern part of the region.
- Several high rainfall events in December 2017, particularly early in the month, contributed to above-average rainfall for that month over most of the southern part of the region.
Figure C2 Total monthly rainfall for the Murray–Darling Basin region during the 2017–18 year compared with the average and percentiles for the region
- Total rainfall during the 3-month period from October–December 2017 was above average. All other months were generally well below average.
- Rainfall in September 2017 was the lowest on record due to dominant high pressure systems that reduced the number of cold fronts and lows that typically occur across the region.
Actual evapotranspiration
Figure C3 Annual and monthly actual evapotranspiration deciles for the Murray–Darling Basin region during the 2017–18 year
- Total area-averaged actual evapotranspiration was below average across most of the region.
- The below-average evapotranspiration is attributed to decreased water availability across the region following well below-average rainfall for most of the year.
- Average to above-average evapotranspiration during October–December 2017 across large parts of the region is likely due to increased water availability following heavy rainfall in October 2017 across southern Queensland and northern New South Wales, as well as high rainfall in December 2017 over most of Victoria and southern New South Wales.
Soil moisture
Figure C4 Annual and monthly soil moisture deciles for the Murray–Darling Basin region during the 2017–18 year
- Soil moisture in the root zone (0–1 m depth) was below average across almost the entire region. Soil moisture in some areas in the northern part of the region was the lowest on record.
- Rainfall and soil moisture are typically closely aligned. For example, the above-average soil moisture in the northern part of the region during October 2017 and in the southern part of the region during December 2017 is due to the above-average rainfall that occurred across these areas during those months.
- Soil moisture was generally well below average throughout the rest of the year due to the relatively poor rainfall that occurred across the region for most of the year.
- More information on soil moisture distribution across the Murray–Darling Basin region is available in the Australian Landscape Water Balance.
Streamflow responses
Streamflow
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.
- The Ovens River represents a predominantly unregulated river in the region.
Figure C6 Total monthly flow for major rivers in the Murray–Darling Basin region during the 2017–18 year compared with average and percentiles
- In the River Murray, streamflow was below average for most of the year. Flow was only above average in April 2018 due to increased releases from upstream reservoirs for operational requirements.
- Total annual flow in the Darling River was only 3% of the average annual flow, which reflects the relatively poor rainfall across the northern part of the region for most of the year.
- The high rainfall in October 2017 across southern Queensland and northern New South Wales had little affect on streamflow in the Darling River due to the very poor soil moisture conditions in these areas prior to the rainfall event. In February 2018, the river did not flow for the entire month.
- In the Ovens River, flow was below average for most of the year. Flow was only above average for two months—August and December 2017—reflecting the periods of the year when rainfall was higher than average over the southern part of the region.
- More information on streamflow distribution across the Murray–Darling Basin region is available in the Regional water information.
Major water reforms
- Two-thirds of the construction of a new 270 km pipeline from the River Murray near Wentworth to Broken Hill was completed in 2017–18. The pipeline will assist in securing long-term water supply for Broken Hill and surrounding communities.