Summary:
- The Barwon-Darling region naturally goes through wetting and drying cycles that can last decades.
- We are currently going through a dry period. The last dry period was 1900 – 1950.
- The cease to flow periods experienced in the most recent drought have been long and severe, but are not unusual when compared to conditions in historical dry periods.
- There are clear differences between the cease to flow periods in the dry, compared to the wet periods.
Climate cycles
The NSW Government has collected rainfall data for approximately 130 years. This data helps us begin to understand some of the long term climate trends in the region. The north-western region of NSW cycles between wet and dry cycles with each cycle lasting decades:
-
1900s – 1950
Comparatively dry period
-
1950 – 2000
Comparatively wet period
-
Post 2000
A return to comparatively dry periods
The driest 10-year and 5-year droughts in all northern valleys and the western region have all occurred during the dry periods.
Cease-to-flow periods
The Barwon-Darling river has often stopped flowing for periods of time. The cease to flow periods in the dry periods of our climate are more frequent than in the wet period.
The cease to flow conditions we saw in the most recent drought were severe and had significant impacts on communities, ecosystems and industries, but they are not unique when compared to the historical record. Our lived experience is mostly drawn from the wet period when there were very few cease to flow periods.
Important information
For this analysis we have used the plain English definition of cease to flow which is zero recorded flow.
Graphs
The graph below shows the number of cease to flow days per year across different points in the Barwon-Darling river.
| Period | Average number of cease | Average duration of cease to flow periods | Duration of longest cease to flow period |
|---|---|---|---|
| 1900 – 1950 | 0.5 | 50 days | 270 days |
| 1950 – 2000 | 0.1 | 60 days | 156 days |
| 2000 – 2021 | 0.7 | 42 days | 326 days |
| Period | Average number of cease | Average duration of cease to flow periods | Duration of longest cease to flow period |
|---|---|---|---|
| 1900 – 1950 | 0.54 | 51 days | 296 days |
| 1950 – 2000 | 0.02 | 127 days | 127 days* |
| 2000 – 2021 | 0.15 | 74 days | 114 days |
* this occurred July – November 1995
| Period | Average number of cease | Average duration of cease to flow periods | Duration of longest cease to flow period |
|---|---|---|---|
| 1900 – 1950 | 0.44 | 66 days | 130 days |
| 1950 – 2000 | 0.16 | 34 days | 80 days |
| 2000 – 2021 | 0.64 | 104 days | 309 days |
| Period | Average number of cease | Average duration of cease to flow periods | Duration of longest cease to flow period |
|---|---|---|---|
| 1900 – 1950 | 0.6 | 66 days | 263 days |
| 1950 – 2000 | 0.06 | 3 days | 4 days |
| 2000 – 2021 | 0.5 | 32 days | 97 days |
Frequently asked questions and presentations
The following frequently asked questions directly relate to the Barwon-Darling and Lower Darling.
This is not correct.
The Darling goes through natural patterns of wet and dry cycles and it is not unusual for the Darling to stop flowing.
Between 1900 to 1950 the Lower Darling stopped flowing 22 times, for an average period of 66 days.
Evidence from our recorded history shows that the longest period of no flow at Weir 32 occurred in 1919-1920 when the river stopped flowing for 236 days.
This is not correct.
The climate of inland NSW goes through natural patterns of wet and dry cycles which often last decades:
1900s – 1950: comparatively dry period
1950 – 2000: comparatively wet period
Post 2000: a return to comparatively dry periods
During the dry periods there are frequent and long periods when the rivers have stopped flowing or are at low levels.
The blue lines in the graphs below show periods of no flows at different gauges in the Barwon-Darling. All gauges show that the river was dry for long periods during the dry climate period from 1900-1950.
Presentation
Download the Barwon-Darling Cease to flow analysis