Burdekin: Climate and water overview
Climate
Rainfall
The total area-averaged rainfall over the region during the year was 443 mm, which is well below the long-term area-averaged rainfall of 650 mm (based on the 1900–2015 period). Annual rainfall ranged from more than 900 mm in the southeast of the region, to less than 300 mm in the northwest of the region (Figure C11).
Figure C11 Total annual rainfall for the Burdekin region during the 2014–15 year
Rainfall during the 2014–15 year was below to very much below average across the northern and central parts of the region with average rainfall in the south (Figure C12). Consequently, flows in the major rivers within the region were much lower than the long-term average (see Streamflow responses).
Figure C12 Annual and monthly rainfall deciles for the Burdekin region during the 2014–15 year
Generally, average rainfall conditions were experienced across much of Australia's northeast 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 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 Indian Ocean Dipole).
During the 2014–15 year, above average rainfall occurred during the early part of the wet season (December–January) although very low rainfall in October and November delayed the start of the wet season. For the remainder of the year (February–June), the region experienced below-average rainfall, particularly during the typically wet months of February–March (Figure C13). The very low rainfall observed during these two wet season months contributed to the well below average streamflow in the region. Even in the southern part of the region where total annual rainfall was equivalent to an average year (Figure C11), annual streamflow in the Bowen and Suttor rivers was well below average (see Streamflow).
This rainfall–runoff behaviour is typical of catchments in northern Australia: periods of high rainfall during the early part of the wet season, when the soil is relatively unsaturated after the dry season, will have much less impact on the runoff in the region compared to periods of high rainfall during the middle of the wet season.
Figure C13 Total monthly rainfall for the Burdekin 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 Burdekin region during the 2014–15 year was 2,347 mm, which is above the long-term area-averaged potential evapotranspiration of 2,283 mm (based on the 1911–2015 period). Potential evapotranspiration was highest in the western central parts of the region and lowest along the areas near the coast (Figure C14).
Figure C14 Total annual potential evapotranspiration for the Burdekin region during the 2014–15 year
Potential evapotranspiration across the Burdekin region was generally above average to very much above average for the 2014–15 year (Figure C15).
Figure C15 Annual potential evapotranspiration deciles for the Burdekin region during the 2014–15 year
Soil Moisture
Figure C16 shows that soil moisture in the root zone (0 to 1m depth) for the 2014–15 year was generally below average in the Burdekin region (compared with the 1911–2015 period).
Figure C16 Annual and monthly soil moisture deciles in the root zone (0 to 1m depth) for the Burdekin region during the 2014–15 year
Figure C16 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 align closely for the majority of months in the 2014–15 year.
The primary reason for the below average streamflow, was the poor wet season rainfall received during February and March (Figure C13). Below average soil moisture conditions across the Burdekin region would also have contributed to the well below average streamflow in the primary rivers of the Burdekin region during the 2014–15 year (see Streamflow).
More information on soil moisture distribution across the Burdekin region is available in the Australian Landscape Water Balance.
Streamflow responses
Significant water events
There were no significant water events in the region during the 2014–15 year.
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 'Contextual information'.
Total annual flows in these rivers during the 2014–15 year were well below the mean annual flow. River flow in the southern part of the region (Bowen–Broken and Suttor–Belyando rivers) was approximately 25–35% of the mean annual flow; flow in the northern part of the region (Burdekin and Cape rivers) was less than 10% of the mean annual flow.
The 3–month period between January–March is usually when the majority of the total annual flow occurs in these rivers. Total flow during this period was well below the long-term average (figures C17–C20), which contributed to the overall below average annual flow during the 2014–15 year.
The flow conditions in the four primary rivers generally reflect the below average rainfall and soil conditions experienced across the region during the year (see Rainfall and Soil moisture); however, the above average rainfall in the early part of the wet season (December–January) did not result in above average streamflows in these rivers. This is presumably because soil water stores and groundwater levels were relatively low following very dry periods during the preceding months of October–November.
Figure C17 Total monthly flow along the Bowen River during the 2014–15 year compared with the long-term average and percentiles for the river
Figure C18 Total monthly flow along the Burdekin River during the 2014–15 year compared with the long-term average and percentiles for the river
Figure C19 Total monthly flow along the Cape River during the 2014–15 year compared with the long-term average and percentiles for the river
Figure C20 Total monthly flow along the Suttor River during the 2014–15 year compared with the long-term average and percentiles for the river
Major water reforms
Major water reforms that occurred during the 2014–15 year included:
- the amalgamation of the former north and south Burdekin water boards to form Lower Burdekin Water; and
- the continuation of the Lower Burdekin Water groundwater monitoring programme with 13 groundwater meters in operation during this reporting period.