South East Queensland: Climate and water overview
Climate conditions
Rainfall
The total area-averaged rainfall over the South East Queensland region during the 2014–15 year was 1,066 mm, which is marginally above the long-term area-averaged rainfall of 1,002 mm (based on the 1900–2015 period). Rainfall ranged from more than 600 mm in the western part of the region to more than 1,800 mm in the southeastern parts of the region (Figure C12). Only 681 mm of rain fell in the region during 2013–14.
Figure C12 Total annual rainfall for the South East Queensland region during the 2014–15 year
Rainfall across the majority of the region was generally average for the 2014–15 year, with a band of above average rainfall to the east (Figure C13). These conditions represent an increase in rainfall compared with the 2013–14 year when below to very much below average rainfall conditions were experienced across the entire South East Queensland region (see the 2014 Account). Streamflows in the major rivers were below average for the second consecutive year but were higher than 2013–14 (see Streamflow responses).
Figure C13 Annual and monthly rainfall deciles for the South East Queensland region during the 2014–15 year
Climate across Australia was largely influenced by persistent near El Niño conditions in the Pacific Ocean from late 2014 and the Bureau of Meteorology declared an El Niño event in May 2015. There were no strong influences on the region from other large-scale drivers during the year (such as the Madden–Julian Oscillation).
Increased streamflows in the major streams is typically observed between between December to March but this did not occur during the 2014–15 year despite average to above average rainfall from December to February. This can be attributed to the very low rainfall and associated dry soil moisture during the preceding months of September–November (Figure C13 and C14).
Figure C14 Total monthly rainfall for the South East Queensland region during the 2014–15 year compared with the long-term average and percentiles for the region
Evapotranspiration
The total area-averaged potential evapotranspiration over the South East Queensland region during the 2014–15 year was 1,845 mm, which is close to the long-term area-averaged potential evapotranspiration of 1,849 mm (based on the 1912–2015 period). Potential evapotranspiration was lower along the coast and in the south, and relatively uniform elsewhere across the region (Figure C15).
Figure C15 Total annual evapotranspiration for the South East Queensland region during the 2014–15 year
For the 2014–15 year, potential evapotranspiration was below average near the coast and generally average across the remainder of the region (Figure C16).
Figure C16 Annual potential evapotranspiration deciles for the South East Queensland region during the 2014–15 year
Soil moisture
Figure C17 shows that soil moisture, in the root zone (0 to 1m depth) for the 2014–15 year was generally average for the region compared with the 1911–2015 period.
Figure C17 Annual and monthly soil moisture deciles in the root zone (0 to 1 m depth) for the South East Queensland region during the 2014–15 year
Figure C17 also shows monthly soil moisture deciles in the root zone (0 to 1m depth) during the 2014–15 year. Comparison of monthly rainfall and soil moisture deciles show the response of soil moisture to changes in rainfall and align closely for most of the 2014–15 year.
Despite generally average rainfall and soil moisture conditions across the region during the 2014–15 year, streamflow in the major river systems was below average (see Streamflow). This can be primarily attributed to the well below average rainfall experienced during a 3-month period prior to the typically high flow months of December–March (Figure C14).
More information on soil moisture distribution across the South East Queensland region is available in the Australian Landscape Water Balance.
Streamflow responses
Significant water events
There were no significant water events or floods in the region during 2014–15.
Streamflow
There are four main river systems within the South East Queensland region:
- Albert
- Bremer
- Brisbane
- Logan.
The location of key gauging stations at Albert River at Bromfleet (Station 145102B), Bremer River at Walloon (Station 143107A), Brisbane River at Savages Crossing (Station 143001C), and Logan River at Yarrahappini (Station 145014A) on these river systems is provided in Figure C6 in 'Physical information'.
Figures C18–C21 show that most monthly flows in the four rivers were below average during the 2014–15 year. The Brisbane River at Savages Crossing (Station 143001C) is located downstream of Wivenhoe Dam and as such, the streamflows (Figure C20) reflect the combined effect of dam release and natural flows.
Streamflows in the major river systems were below expected given the average to above average rainfall across the region for the 2014–15 year. This was primarily due to low rainfall (see Rainfall) and soil moisture (see Soil moisture) conditions prior to the typically high flow months of December to March. The influence of low antecedent rainfall and soil moisture conditions on streamflow was similarly observed in August 2014 when high rainfall (greater than the 90th percentile) resulted in lower than expected streamflows.
Above average rainfall during April and May resulted in relatively high soil moisture and a distinct response in streamflow.
Whilst total annual flow volumes for all four rivers were below the mean annual flow in 2014–15, they were higher than streamflows during the 2013–14 year due to comparatively higher rainfall.
Figure C18 Total monthly flow along Albert River during the 2014–15 year compared with long-term average and percentiles for the river
Figure C19 Total monthly flow along Bremer River during the 2014–15 year compared with long-term average and percentiles for the river
Figure C20 Total monthly flow along Brisbane River during the 2014–15 year compared with long-term average and percentiles for the river
Figure C21 Total annual monthly flow along Logan River during the 2014–15 year compared with long-term average and percentiles for the river
Major water reforms
Amendments have been proposed to the Moreton water resource plan and resource operations plan relating to water allocation and management in the Central Lockyer Valley water supply scheme. These changes, which will be implemented in 2017, seek to:
- convert supplemented surface water and groundwater authorisations to volumetric water allocations
- improve infrastructure operation and water sharing rules to ensure a more equitable share of the water resource across all water users in the scheme
- establish water trading arrangements for both surface water and groundwater users in the scheme.
The proposed amendments to establish volumetric water allocations will support recommendations of the Queensland Competition Authority's Seqwater Irrigation Price Review. Converting water entitlements to tradeable water allocations will create a more secure and flexible water management framework to support sustainable agricultural development in the Central Lockyer Valley.
Seqwater has completed investigations to upgrade Lake Macdonald Dam, and also commenced preliminary design for the future upgrade of Lake Kurwongbah (Sideling Creek Dam) and Leslie Harrison Dam (Seqwater 2015). The first phase in the development of a 30-year plan to meet the region’s future water supply needs was completed in the 2014–15 year.