National Water Account 2017

Canberra: Climate and water

Annual rainfall for the region was slightly below average. A large proportion of the annual rainfall occurred in September 2016; the second-wettest September on record. This rainfall contributed to very high streamflows across the region during September–October 2016. Rainfall and streamflow throughout most of the year were below average.

 

 

For further information on the region's climate and water conditions during the 2016–17 year scroll down this page or click on the links below:

 

About the region

The Canberra region has a relatively dry, continental climate with warm to hot summers and cool to cold winters. Rainfall in the region is almost equally distributed throughout the year with a long-term monthly average of 50–75 mm.

The main rivers in the region are the Molonglo, Cotter and Queanbeyan rivers, which all contribute to the Murrumbidgee River. The majority of flow typically occurs during autumn and winter when evapotranspiration is relatively low. Streamflows in the Murrumbidgee can also be influenced by water diversions from the Snowy Mountain Scheme.

 

Climate conditions

Rainfall

Figure C1 Annual and monthly rainfall deciles for the Canberra region during the 2016–17 year

 

  • Total area-averaged rainfall for the year was 761 mm, slightly below the mean annual rainfall of 796 mm.
  • Very high rainfall occurred in September 2016, with northern parts of the region recording their highest September rainfall on record.
  • Rainfall in June 2017 was very low; more than 50% of the region experienced its driest June on record.

 

Total monthly rainfall for the Canberra region during the 2016-17 year compared with the long term average and percentiles for the region
Figure C2 Total monthly rainfall for the Canberra region during the 2016–17 year compared with the long-term average and percentiles for the region

 

  • In the first three months of year (July–September), the climate was influenced by a negative Indian Ocean Dipole phase that is associated with higher winter–spring rainfall. Rainfall across the region was above average during this 3-month period, particularly in September where rainfall was well above the 90th percentile for the month and was the second wettest September on record.
  • Rainfall was well below average during the summer months, particularly January–February 2017.
  • Persistent rainfall during March 2017, including a heavy thunderstorm on 21 March, contributed to the above-average rainfall for that month.
  • Rainfall in June 2017 was well below the 10th percentile 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 for the Canberra region during the 2016–17 year

 

  • Total area-averaged actual evapotranspiration was 676 mm, higher than the mean value of 646 mm.
  • The above-average evapotranspiration may be attributed to a combination of above-average temperatures across the region and increased water availability, particularly following high rainfall in September 2016 and, to a lesser extent, March 2017.

 

Figure C4 Total monthly actual evapotranspiration for the Canberra region during the 2016–17 year compared with the long-term average and percentiles for the region

 

  • Actual evapotranspiration was above average for most months of the year.
  • Evapotranspiration was only below average during a 3-month period (January–March) when water availability was low due to relatively poor rainfall during the summer months of January–February.

 

Soil moisture

Figure C5 Annual and monthly soil moisture deciles for the Canberra region during the 2016–17 year

 

  • Soil moisture in the root zone (0–1 m depth) was average to above average across most of the region.
  • Rainfall and soil moisture are typically closely aligned. For example, very much above-average soil moisture during September–October 2016 reflects the heavy rainfall that occurred during September.
  • More information on soil moisture distribution across the Canberra region is available in the Australian Landscape Water Balance.

 

Streamflow responses

Key flow gauging stations along the main rivers within the Canberra region
Figure C6 Key flow gauging stations along the main rivers within the Canberra region
 

 

  • The Cotter and Queanbeyan rivers contribute most of the inflows to the storages in the Canberra region.
  • Molonglo River, one of the major tributaries of Murrumbidgee River, runs through the Canberra city centre where it is dammed to form Lake Burley Griffin.

 

Figure C7 Total monthly flow for key rivers during the 2016–17 year compared with long-term average and percentiles

 

  • Streamflow was generally below average for the majority of the year.
  • Most of the annual streamflow occurred during September–October 2016. The well above-average monthly flow during this 2-month period was due to heavy rainfall during September 2016 across the entire region.
  • High flows in July 2016 were primarily attributed to record rainfall that occurred in June 2016, which included an east coast low event that impacted the region (see 2016 Account).
  • There was little flow response following the above-average rainfall in March 2017, which can be attributed to the relatively low soil moisture conditions across the region following a very dry summer.