Skip to content

An analysis of South-East QLD rainfall and catchment levels between 1899–2022.

Notifications You must be signed in to change notification settings

mnperic/seq-rainfall-catchment

Repository files navigation

South-East QLD Rainfall and Catchment Levels

An analysis of historical South-East QLD rainfall and catchment levels.

Overview

The purpose of this study was to analyse historical total/average rainfall amounts and dam catchment levels for South-East Queensland.

This study was conducted in relation to analysing potential trends over multiple significant weather events, including the 2011 Brisbane Floods and the recent and ongoing 2022 Eastern Australian Floods.

The investigation was split into two areas:

  1. Calculating and analysing total/average SEQ rainfall from 1899–2022 and,
  2. Calculating and analysing SEQ dam catchment levels from 2017–2022.

The wide time-span of 1899–2022 was chosen to provide context of recent weather events amongst historical SEQ rainfall data.

Similarly, the time-span of 2017–2022 was chosen to highlight and identify potential trends in relation to the ongoing 2022 Eastern Australian Floods.

Analysis

For this study, the Alderley Weather Station (Station 040224) in Brisbane's inner-north was chosen to analyse total/average historical rainfall.

Total Historical Rainfall

rainfall_historical

As is evident in the charts, there was a significantly reduced amount of rainfall during the period of 2005–2010, which coincided with the QLD Government's introduction of a series of water restrictions.

The chart also shows a trend in the gradual increase of rainfall towards the end of this period, which ultimately led to the easing of water restrictions. However, this trend also shows an ongoing increase in rainfall during this period, which may correlate to the region's flooding events in 2011.

Conversely, there is a downward trend towards the latter-half of the decade where total rainfall gradually eased. However, on 28 February 2022 a new single-day rainfall record was broken, with the region receiving 344 mm of rain in just one day – beating the 114-year-old record of 308 mm set in March 1908.

Average Monthly Rainfall

rainfall_month_average

The above chart shows a clear positive trend in the increase of average monthly rainfall during summer compared to winter. This seasonal variance also correlates with the region's humid sub-tropical climate and tendency to receive more rainfall during the Queensland 'wet' season (November–March).

Catchment Levels

For this study, the total SEQ Water Grid was analysed to investigate total capacities, current volumes and operating statuses of SEQ catchments. The figures in the chart below were accurate as of 9:00am 7 March 2022.

Catchment Area Capacity (ML) Current Volume (ML) Percent (%) Current Status
Atkinson Dam 30401.0 30742.0 101.12% Over Capacity
Bill Gunn Dam 6947.0 6629.0 95.42% Near Capacity
Borumba Dam 46000.0 48022.0 104.40% Over Capacity
Cedar Pocket Dam 735.0 769.0 104.63% Over Capacity
Cooloolabin Dam 8183.0 8250.0 100.82% Over Capacity
Enoggera Dam 4262.0 4445.0 104.29% Over Capacity
Ewen Maddock Dam 16587.0 17246.0 103.97% Over Capacity
Gold Creek Resevoir 810.0 952.0 117.53% Over Capacity
Hinze Dam 28.0497 338595.0 108.97% Over Capacity
Lake Baroon 61000.0 61851.0 101.40% Over Capacity
Lake Clarendon 24276.0 8599.0 35.42% Low Capacity
Lake Kurwongbah 14192.0 14721.0 103.73% Over Capacity
Lake Macdonald 8018.0 8354.0 104.19% Over Capacity
Lake Manchester 26217.0 26485.0 101.02% Over Capacity
Tingalpa Resevoir 13206.0 14899.0 112.82% Over Capacity
Little Nerang Dam 6705.0 6793.0 101.31% Over Capacity
Maroon Dam 44319.0 44457.0 100.31% Over Capacity
Moogerah Dam 83765.0 88714.0 105.91% Over Capacity
Nindooinbah Dam 208.0 275.0 132.21% Over Capacity
North Pine Dam 214302.0 144067.0 67.23% Low Capacity
Poona Dam 655.0 586.0 89.47% Near Capacity
Somerset Dam 379849.0 297873.0 78.42% Near Capacity
Wappa Dam 4694.0 4731.0 100.79% Over Capacity
Wivenhoe Dam 1165240.0 1120710.0 96.18% Near Capacity
Wyaralong Dam 102883.0 106317.0 103.34% Over Capacity


Which, when visualised, reveals an unsuprising trend in the current status of a majority of SEQ's catchment areas.

catchment_pie

The following figure charts total catchment levels during the period of 2007–2022, indicating the surge in total rainfall in the region in early 2022.

catchment_line

Considerations

  1. It must be noted that the upward trend in total rainfall during the 2010–2011 summer period was not the sole variable or cause of the 2011 Brisbane Floods. This significant flooding event was caused via a mixture of heavy rain over the period and the release of excess water from the SEQ Water Grid, as outlined in a 2011 Macquarie University report.

  2. There is a potential data anomaly/outlier during the early 1900s and 2000s which may alter findings, albeit insignificantly.

References

Bureau of Meteorology, 2022, Weather stations, http://www.bom.gov.au/climate/data/stations/

SEQ Water, 2022, Dam Levels, data, https://www.seqwater.com.au/historic-dam-levels

SEQ Water, 2022, Historic Dam Levels, data, https://www.seqwater.com.au/historic-dam-levels

Van den Honert, Robin C., McAneney, J., 2011, The 2011 Brisbane Floods: Causes, Impacts and Implications, https://www.mdpi.com/2073-4441/3/4/1149/htm