4610.0.55.007 - Water and the Murray-Darling Basin - A Statistical Profile, 2000-01 to 2005-06  
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Contents >> Attributes of the Murray-Darling Basin >> Rainfall and water availability

RAINFALL AND WATER AVAILABILITY

The climate of the MDB is relatively dry compared to other regions of Australia (map 1.8). Annual rainfall in 2005-06 was lower in the MDB than in the tropical north, eastern seaboard and south-west of the continent, as well as in Tasmania. However, most of the Basin received more rainfall than central Australia.

1.8 TOTAL RAINFALL - 2005-06
Diagram: 2.8 TOTAL RAINFALL—2005–06


Based on long-term averages, the MDB receives 530,618 GL of rainfall annually, of which 94% is evaporated or transpired (table 1.9). Almost 2% of rainfall enters the soil and groundwater as deep drainage. In the MDB, approximately 23,609 GL or 4% of rainfall appears as run-off. Run-off is "the part of precipitation in a given area and period of time that appears as streamflow" (NWC 2007:87).

Proportionally more evapotranspiration (94% of rainfall) occurs in the MDB than for the whole of Australia (89%). This results in less rainfall being transformed into run-off in the MDB (4% of rainfall) compared with the whole of Australia (9%). This means that rainfall is less likely to become available for use from river basins in the MDB.

1.9 Annual water balance - 2008

Murray-Darling Basin
Australia
Volume
Proportion of rainfall
Volume
Proportion of rainfall
Water balance component
GL
%
GL
%

Rainfall(a)
530 618
100
3 704 913
100
Evapotranspiration
497 290
94
3 291 649
89
Run-off
23 609
4
349 431
9
Deep drainage
9 719
2
63 833
2

(a) Components may not add to rainfall total due to rounding.
Source: Bureau of Rural Sciences, 2008, Rural Water, viewed 9 July 2008, http://adl.brs.gov.au/water2010/index.phtml
Note: Data relates to long-term averages, and is not indicative of a single period of time.



Regional distribution of rainfall

The spatial distribution of rainfall in the MDB is important as an indicator for vegetation growth - a key driver for agricultural production in Australia. In 2005-06, the highest levels of rainfall occurred in the south eastern and eastern areas of the MDB, declining towards the western and north western boundary as shown in map 1.10.

1.10 TOTAL RAINFALL, Murray-Darling Basin-2005-06
Diagram: 2.10 TOTAL RAINFALL, Murray–Darling Basin–2005–06


The distribution of rainfall across the river basins within the MDB is extremely variable. Based on long-term averages, annual rainfall (expressed in volume terms) is highest in the Condamine-Culgoa (85,755 GL), Murrumbidgee (48,691 GL) and Lachlan (46,120 GL) river basins (table 1.11). Rainfall is lowest in the Lake George (686 GL), Kiewa (2,374 GL) and Campaspe (2,658 GL) river basins.

Rainfall expressed volumetrically is influenced by the size of each river basin. Generally, larger river basins have higher rainfall volumes. Therefore, in area-adjusted (GL/km2) terms, river basins with the highest concentration of rainfall are the Kiewa (1.24 GL/km2), Upper Murray (1.18 GL/km2) and Ovens (1.06 GL/km2) river basins.

At the river basin level, more run-off occurs in the Upper Murray (4,472 GL), Murrumbidgee (3,831 GL) and Goulburn (2,686 GL) river basins compared with others. Run-off also exceeds 1,000 GL in the Ovens, Macquarie-Bogan, Lachlan, Namoi, Condamine-Culgoa and Border Rivers basins. Some parts of the MDB have negligible run-off, for example, the Paroo (1 GL), Benanee (3 GL) and Darling (6 GL) river basins (table 1.11).

1.11 Average annual rainfall and runoff, by river basin - Murray-Darling Basin - 2008

Rainfall
Area
Run-off
River basin
km2
GL
GL/km2
GL

Avoca River
14 182
5 621
0.40
95
Benanee
21 345
6 778
0.32
3
Border Rivers
48 031
32 582
0.68
1 199
Broken River
7 096
4 466
0.63
341
Campaspe River
4 050
2 658
0.66
250
Castlereagh River
17 420
10 377
0.60
346
Condamine-Culgoa Rivers
162 595
85 755
0.53
1 212
Darling River
112 834
35 539
0.31
6
Goulburn River
16 860
14 613
0.87
2 686
Gwydir River
26 593
18 123
0.68
753
Kiewa River
1 908
2 374
1.24
676
Lachlan River
90 874
46 120
0.51
1 565
Lake George
944
686
0.73
66
Loddon River
15 658
7 796
0.50
349
Lower Murray River
58 261
16 764
0.29
207
Macquarie-Bogan Rivers
74 775
42 583
0.57
1 648
Mallee
41 498
13 210
0.32
37
Moonie River
14 341
8 023
0.56
106
Murray-Riverina
15 055
6 279
0.42
109
Murrumbidgee River
81 641
48 691
0.60
3 831
Namoi River
42 004
28 675
0.68
1 377
Ovens River
7 979
8 425
1.06
1 727
Paroo River
73 944
23 591
0.32
1
Upper Murray River
15 342
18 077
1.18
4 472
Warrego River
62 945
29 597
0.47
181
Wimmera-Avon Rivers
30 374
13 216
0.44
368
Murray Darling Basin(a)
1 058 549
530 618
0.50
23 609

(a) Components may not add to total due to rounding.
Source: Bureau of Rural Sciences, 2008, Rural Water, viewed 9 July 2008, http://adl.brs.gov.au/water2010/index.phtml
Note: Data relates to long-term annual averages, and is not indicative of a particular year.


The inter-relationship between rainfall, temperature, topography and geology affect the pattern of run-off in the Australia and the MDB (map 1.12). This is significant because it influences where water becomes available for use by society and the environment. Based on long-term averages, annual run-off levels are highest in the north eastern Victoria and south eastern New South Wales river basin sub-catchments, and lowest in the western and north western sub-catchments (map 1.13).

1.12 MEAN ANNUAL RUN-OFF IN AUSTRALIAN SUBCATCHMENTS, Murray-Darling Basin-2008
Diagram: 2.12 MEAN ANNUAL RUN-OFF IN AUSTRALIAN SUBCATCHMENTS, Murray-Darling Basin—2008


1.13 ENLARGEMENT, mean annual run-off, Murray-Darling Basin subcatchments-2008
Diagram: 2.13 ENLARGEMENT, mean annual run-off, Murray-Darling Basin subcatchments—2008



Rainfall anomalies 2000-01 to 2005-06

Rainfall anomalies measure the deviation from the long-term average (1960-1990) rainfall for given locations (BoM 2008). The rainfall anomalies across Australia are described in the following section and illustrated in maps 1.14 and 1.15, for the period 2000-01 to 2006-07.

2000-01

In 2000-01, average levels of rain fell in the majority of the MDB. Northern and central Australia experienced more rainfall than normal.

2001-02

The 2001-02 year was drier than average in the majority of the MDB, but not as severe as 2002-03. This pattern was similar to the trend over most of the rest of Australia, except in central Australia which was wetter than average.

2002-03

The 2002-03 year was extremely dry throughout the MDB, particularly in the eastern and south eastern areas of the Basin where rainfall is usually highest (see map 1.10). The resulting reduction in catchment run-off severely affected water storage levels in large dams (see Chapter 3, graph 3.18). The reduced rainfall experienced in the MDB was reflected over most of eastern Australia in 2002-03. The northern part of the Northern Territory was wetter than usual, but far north Queensland was much drier.

2003-04

The 2003-04 year was drier than average in the MDB, but not as dry as the previous two years. Northern and central Australia received more rainfall than normal.

2004-05

The 2004-05 year was drier than average in the MDB, and geographically exhibited a similar rainfall anomaly pattern to 2003-04. Many areas of north eastern, north western, northern and central Australia were drier than normal.

2005-06

The 2005-06 year was drier than average in the MDB, especially in the northern part of the Basin. North eastern, north western, northern, and central Australia experienced more rainfall than normal.

2006-07

The 2006-07 year was extremely dry throughout the MDB, particularly in the eastern, northern and south eastern areas of the Basin where rainfall is usually highest (see map 1.10).

1.14 RAINFALL ANOMALIES, Murray-Darling Basin-2000-01 to 2003-04
Diagram: 2.14 RAINFALL ANOMALIES, Murray–Darling Basin–2000–01 to 2003–04


1.15 RAINFALL ANOMALIES, Murray-Darling Basin-2004-05 to 2006-07
Diagram: 2.15 RAINFALL ANOMALIES, Murray–Darling Basin–2004–05 to 2006–07






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