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Analysis and insights

Cease to flow

Find out more about the climate cycles and cease to flow periods for the last 130 years in the Barwon-Darling region.

Darling River at Pooncarie.
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:

  1. 1900s – 1950

    Comparatively dry period

  2. 1950 – 2000

    Comparatively wet period

  3. 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

Barwon-Darling

The graph below shows the number of cease to flow days per year across different points in the Barwon-Darling river.

Cease to flow periods at different locations along the Barwon-Darling River since the early 1900s.

Walgett

Cease-to-flow at Walgett

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

Brewarrina

Cease-to-flow at Brewarrina

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

Wilcannia

Cease-to-flow at Wilcannia

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

Weir 32

Cease-to-flow at Weir 32

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