Murray–Darling Basin
Climate overview

Rainfall

Rainfall across the Murray–Darling Basin (MDB) region was generally below average for the 2012–13 year (Figure C1). The total area-averaged rainfall over the MDB region during the 2012–13 year was 377 mm, which is below the long-term area-averaged rainfall of 471 mm based on 1900–2013 data. Particularly, MDB areas within Queensland and Victoria recorded very much below average rainfall during the 2012–13 year.

These conditions represent a decrease in rainfall compared to the 2011–12 year (see 2012 Account), when rainfall was generally above average. This contributed to decreased inflow volumes into the water storages during the 2012–13 year.

 

Figure C1 Map of annual rainfall deciles for the Murray–Darling Basin region during the 2012–13 year
Figure C1 Map of annual rainfall deciles for the Murray–Darling Basin region during the 2012–13 year


Annual rainfall ranged from more than 1,200 mm in southern areas of the region (along the Great Dividing Range in Victoria), to less than 200 mm in western parts of the region (Figure C2). 


 
Figure C2 Map of total annual rainfall for the Murray–Darling Basin region during the 2012–13 year
Figure C2 Map of total annual rainfall for the Murray–Darling Basin region during the 2012–13 year


Generally below-average rainfall was experienced across much of Australia during the 2012–13 year. There were no strong influences from large-scale climate drivers over the 2012–13 year. Conditions in the Pacific Ocean were neutral and a negative Indian Ocean Dipole event developed during winter 2013 (at the end of the 2012–13 year).

 

The area-averaged monthly rainfall was below the long-term average for most months during the 2012–13 year, with the exception of July 2012, March 2013, and June 2013 (Figure C3). Seven consecutive months (August 2012 – February 2013) recorded values well below the long-term area-average. October 2012 was a particularly dry month for the MDB region, ranking below the 10th percentile.


Figure C3 Graph of total monthly rainfall for the Murray–Darling Basin region during the 2012–13 year compared with the long-term average and percentiles for the region
Figure C3 Graph of total monthly rainfall for the Murray–Darling Basin region during the 2012–13 year compared with the long-term average and percentiles for the region

Evapotranspiration

Figure C4 shows that actual evapotranspiration was generally average or below average in the region during the 2012–13 year.This was influenced by generally below average rainfall which limited water availability and above average temperature across the region.


Figure C4 Map of annual evapotranspiration deciles for the Murray–Darling Basin region during the 2012–13 year
Figure C4 Map of annual evapotranspiration deciles for the Murray–Darling Basin region during the 2012–13 year


The total area-averaged actual evapotranspiration over the MDB region during the 2012–13 year was 376 mm, which is below the long-term area-averaged actual evapotranspiration of 433 mm based on 1911–2012 data. During the 2012–13 year, evapotranspiration across the MDB region was highest in areas close to northern, eastern, and southeastern boundaries of the region and lowest in southwestern areas (Figure C5).


Figure C5 Map of total annual evapotranspiration for the Murray–Darling Basin region during the 2012–13 year
Figure C5 Map of total annual evapotranspiration for the Murray–Darling Basin region during the 2012–13 year

Temperature

The MDB region experienced mean temperatures generally above the long-term average during the 2012–13 year (Figure C6). A large area in the southwest of the region recorded mean temperatures very much above average, whilst northern parts were closer to the long-term average. 
 


Figure C6 Map of annual mean temperature deciles for the Murray–Darling Basin region during the 2012–13 year
Figure C6 Map of annual mean temperature deciles for the Murray–Darling Basin region during the 2012–13 year


Mean temperatures across the MDB region ranged from more than 22 °C in the northwest of the region to less than 10 °C in isolated areas along the southeast border (Figure C7).


Figure C7 Map of annual mean temperature for the Murray–Darling Basin region during the 2012–13 year
Figure C7 Map of annual mean temperature for the Murray–Darling Basin region during the 2012–13 year


Monthly mean temperatures for the MDB region were above the long-term average for all months during the 2012–13 year, with the exception of August 2012 (Figure C8). November 2012 and January 2013 both ranked above the 90th percentile, with the MDB region experiencing its ninth-warmest November and seventh-warmest January on record.

 

Figure C8 Graph of average monthly mean temperature for the Murray–Darling Basin region during the 2012–13 year compared with the long-term average and percentiles for the region
Figure C8 Graph of average monthly mean temperature for the Murray–Darling Basin region during the 2012–13 year compared with the long-term average and percentiles for the region