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Murray–Darling Basin

                                                                                                   

Climate Overview

                             

Maps and graphs provide a summary of the rainfall, evaporation and temperature data for the reporting period.

 

Rainfall

The total area-averaged rainfall over the Murray–Darling Basin (MDB) region during 2009–10 was 528 mm, which is above the mean annual rainfall of 467 mm. Figure C1 shows that most of the region recorded above average rainfall, particularly over the northwest of the region, which recorded very much above average rainfall. Below average rainfall only occurred over the northeast of the region.

 

Figure C1. Annual rainfall deciles for the MDB region during 2009–10

Figure C1. Annual rainfall deciles for the MDB region during 2009–10

During 2009–10, rainfall across the MDB region was highest in the alpine areas of the southeast and lowest around the more arid areas of inland New South Wales and South Australia in the southwest of the region, shown in Figure C2. This distribution of rainfall across the region during the reporting period is similar to the long-term average rainfall pattern, as shown in Figure C3.

Figure C2. Total annual rainfall for the MDB region during 2009–10

Figure C2. Total annual rainfall for the MDB region during 2009–10

Figure C3. Average annual rainfall for the MDB region, based on data collected 1961–90

Figure C3. Average annual rainfall for the MDB region, based on data collected 1961–90

Rainfall for the September–November period was below average during 2009–10 due to the El Niño event yielding drier conditions across the region (Figure C4). During December, the El Niño event began to weaken and the early stages of a La Niña became apparent, which resulted in high rainfall across the region for most the remainder of the reporting period. It was the fourth wettest March on record for the region, and the wettest February since 1976.

 

Figure C4. Total monthly rainfall for the MDB region during 2009–10 compared against the long-term percentiles for the region

Figure C4. Total monthly rainfall for the MDB region during 2009–10 compared against the long-term percentiles for the region

 

Evapotranspiration

The total area-averaged evapotranspiration (ET) over the MDB region during 2009–10 was 428 mm, which is only slightly above the mean annual ET of 421 mm. Figure C5 shows that ET was mainly above average across most of the northwestern part of the region during 2009–10. Throughout most of the southern and eastern parts of the region, ET was generally equivalent to average to below average conditions.

 

Figure C5. Annual evapotranspiration deciles for the MDB region during 2009–10

Figure C5. Annual evapotranspiration deciles for the MDB region during 2009–10

During 2009–10, ET across the MDB region was highest in the alpine areas of the southeast and lowest around the more arid areas of inland New South Wales and South Australia in the southwest of the region around Broken Hill, as shown in Figure C6. This distribution of ET across the region during the reporting period is similar to the long-term average ET pattern (Figure C7).

 

Figure C6. Total annual evapotranspiration for the MDB region during 2009–10

Figure C6. Total annual evapotranspiration for the MDB region during 2009–10

Figure C7. Average annual evapotranspiration for the MDB region, based on data collected 1911–2010

Figure C7. Average annual evapotranspiration for the MDB region, based on data collected 1911–2010

Temperature

Figure C8 shows that most of the region experienced above average to very much above average maximum daily temperatures during 2009–10. This can be attributed to the influence of the El Niño event. The areas in the southwest of the MDB region and in the northeast around Inverell experienced the highest maximum daily temperatures on record.

 

Figure C8. Annual maximum daily temperature deciles for the MDB region during 2009–10

Figure C8. Annual maximum daily temperature deciles for the MDB region during           2009–10

Figure C9. Annual mean maximum daily temperature for the MDB region during 2009–10

Figure C9. Annual mean maximum daily temperature for the MDB region during             2009–10

Maximum daily temperatures across the MDB region during 2009–10 were highest in the arid areas of Queensland in the north and lowest in the alpine areas of the southeast (Figure C9). This temperature pattern across the region during the reporting period is similar to the long-term average conditions (Figure C10).

Figure C10. Average annual maximum daily temperature for the MDB region, based on data collected 1961–90

Figure C10. Average annual maximum daily temperature for the MDB region, based on data collected 1961–90

The area-averaged annual maximum daily temperature for the region during 2009–10 was the third highest on record. Maximum daily temperatures were the highest on record in November and the second highest on record in August (Figure C11).

 

Figure C11. Average monthly maximum daily temperatures for the MDB region during 2009–10 compared against the long-term percentiles for the region

Figure C11. Average monthly maximum daily temperatures for the MDB region during 2009–10 compared against the long-term percentiles for the region