Burdekin: Climate and water
Annual rainfall in the region was below average during the 2015–16 year, which resulted in below average streamflow conditions in all of the main river systems across the region. Wet season rainfall did, however, lead to improved streamflow conditions, particularly in the Burdekin River when compared to the previous year.
Introduction
The Burdekin region lies within the dry tropics of northern Australia, which has a distinct and predictable climatic seasonality. Almost all rainfall in the region occurs during the wet season (November–April). As a consequence, flow in the rivers is strongly seasonal (see Water resources in 'Region description' for more information).
Climate conditions
Rainfall
Generally, below average rainfall conditions were experienced across much of northern Australia during the 2015–16 year. Climate across Australia was largely influenced by strong El Niño conditions in the Pacific Ocean; one of the strongest El Niño events since 1950. During the early part of the wet season (September–November), Australia's climate was also influenced by a positive phase of the Indian Ocean Dipole, which also contributed to the relatively dry conditions throughout northern Australia.
The total area-averaged rainfall across the region during the year was 500 mm, which is below the long-term area-averaged rainfall of 650 mm (based on the 1900–2016 period). Annual rainfall ranged from more than 900 mm in the east of the region, to less than 300 mm in central parts of the region (Figure C1).
Figure C1 Total annual rainfall for the Burdekin region during the 2015–16 year
Figure C2 Annual and monthly rainfall deciles for the Burdekin region during the 2015–16 year
Rainfall during the 2015–16 year was below average across much of the northern and central parts of the region (Figure C2). Below average rainfall occurred in the lead up (September–October) and during the wet season (November–April). In contrast, above average rainfall was recorded in March and, unusually for late June, as a result of two large storm events associated with east coast lows extending into the region (Figure C3).
Figure C3 Total monthly rainfall for the Burdekin region during the 2015–16 year compared with the long-term average and percentiles for the region
Evapotranspiration
The total area-averaged potential evapotranspiration over the Burdekin region during the 2015–16 year was 2,316 mm, which was above the long-term area-averaged potential evapotranspiration of 2,276 mm (based on the 1911–2016 period). Potential evapotranspiration was highest in the western central parts of the region and lowest along the areas near the coast (Figure C4).
Typical of the climate conditions across northern Australia, annual potential evapotranspiration over the Burdekin region was much greater than the total annual rainfall. This means that on an annual basis the landscape is generally dry and can be described as water-limited (CSIRO 2009b). Only during high-rainfall periods in the wet season does rainfall exceed potential evapotranspiration, which drives the seasonal streamflow.
Figure C4 Total annual potential evapotranspiration for the Burdekin region during the 2015–16 year
Potential evapotranspiration across the Burdekin region was generally above average to very much above average in response to very high temperatures and decreased rainfall (and hence cloud cover) experienced across the region during the 2015–16 year (Figure C5).
Figure C5 Annual potential evapotranspiration deciles for the Burdekin region during the 2015–16 year
Soil moisture
Soil moisture in the root zone (0–1m depth) during the 2015–16 year was generally below average to much below average in the Burdekin region, compared with the 1911–2016 period.
Figure C6 Annual and monthly soil moisture deciles in the root zone (0 to 1m depth) for the Burdekin region during the 2015–16 year
Comparison of monthly rainfall and soil moisture deciles indicates close alignment for the majority of months in the 2015–16 year. Mid-season rainfall, particularly in the Burdekin delta area provides a double benefit; as increased rainfall results in reduced irrigation and increased recharge to surface water and shallow groundwater storages.
More information on soil moisture distribution across the Burdekin region is available in the Australian Landscape Water Balance.
Streamflow responses
Streamflow
There are four primary river systems within the Burdekin region:
- Bowen–Broken
- Burdekin
- Cape
- Suttor–Belyando.
More detail on these river systems, including location, is provided in the Surface water section of the 'Region description'. The locations of key gauging stations along these rivers are provided in Figure R7 in 'Region description'.
The below average rainfall conditions experienced across the region contributed to below average flows in the region's main river systems during the year. Annual flow in the southern part of the region (Bowen–Broken and Suttor–Belyando rivers) was 30–40% of the mean average annual flow; flow in the northern part of the region (Burdekin and Cape rivers) was less than 30% of the mean average annual flow (figures C7–C10). Compared with the previous year, the increased rainfall during the typically wettest months of the year (January to March, see Rainfall) resulted in considerably higher flows observed in the Burdekin River (Station 120002C).
Figure C7 Total monthly flow along the Bowen River during the 2015–16 year compared with the long-term average and percentiles for the river
Figure C8 Total monthly flow along the Burdekin River during the 2015–16 year compared with the long-term average and percentiles for the river
Figure C9 Total monthly flow along the Cape River during the 2015–16 year compared with the long-term average and percentiles for the river
Figure C10 Total monthly flow along the Suttor River during the 2015–16 year compared with the long-term average and percentiles for the river
Major water reforms
Major water reforms that occurred during the 2015–16 year included:
- an initiative that grants users groundwater harvesting permits to extract water in addition to their licensed volume. The initiative will assist in managing rising groundwater levels in the north of the region
- the continuation of the Lower Burdekin Water groundwater monitoring programme with 12 additional groundwater meters installed with telemetry during the 2015–16 year, and
- plans to amend the Burdekin Basin Water Resource Plan for catchments above Burdekin Falls Dam have been developed for possible implementation in 2017