National Water Account 2018

Fitzroy: Climate and water

  • Rainfall was higher than average in October 2017 and February 2018; all other months had below-average rainfall.
  • Streamflow during the wet season was well below average across the region.

 

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For further information on the region's climate and water conditions during the 2017–18 year scroll down this page or click on the links below:

 

About the region

  • The Fitzroy region has a sub-tropical, semi-arid climate with a high inter-annual variability in rainfall and streamflow. There is a strong seasonality in rainfall patterns with most of the rain falling in the wet season (November–April). As a consequence, flow in the rivers is strongly seasonal and many of the region's rivers cease to flow during the dry season (May–October).

 

Climate conditions

Rainfall


Figure C1 Annual and monthly rainfall deciles for the Fitzroy region during the 2017–18 year

 

  • Total area-averaged rainfall for the year was 574 mm, less than the mean value of 663 mm.
  • A surface trough and upper level disturbance contributed to well above-average rainfall across much of the region in October 2017 with some coastal areas recording their highest October rainfall on record.
  • The well above-average rainfall in February 2018 was a result of severe thunderstorms and showers that mainly impacted the southern half of the region.

 

 

Figure C2 Total monthly rainfall for the Fitzroy region during the 2017–18 year compared with the average and percentiles for the region

 

  • 55% of the total annual rainfall occurred in October 2017 and February 2018 combined.
  • October rainfall was more than three times the average for the month.

 

Actual evapotranspiration


Figure C3 Annual and monthly actual evapotranspiration deciles for the Fitzroy region during the 2017–18 year

 

  • Total area-averaged actual evapotranspiration was average to below average across most of the region.
  • Below-average evapotranspiration during the dry season months of July–September 2017 was likely due to the decreased water availability following a dry start to the year.
  • The above-average evapotranspiration that occurred during October–December 2017 and February–April 2018 may be due to the increased water availability following high rainfall in October 2017 and February 2018 respectively.

 

Soil moisture

 


Figure C5 Annual and monthly soil moisture deciles in the root zone (0–1 m depth) for the Fitzroy region during the 2017–18 year

 

  • Soil moisture in the root zone (0–1m depth) was generally below-average across most of the region.
  • Rainfall and soil moisture are typically closely aligned. For example, above-average soil moisture conditions during October–November 2017 and March 2018 are due to the well above-average rainfall that occurred during October 2017 and February 2018 respectively. Below-average soil moisture throughout the rest of the year reflect the relatively poor rainfall conditions that occurred during most months of the year.
  • More information on soil moisture distribution across the Fitzroy region is available in the Australian Landscape Water Balance.

 

Streamflow responses

Streamflow


Figure C6 Key flow gauging stations along the main rivers within the Fitzroy region

 

  • The six main rivers in the region are the Fitzroy, Dawson, Nogoa, Mackenzie, Isaac, and Comet rivers, which correspond to the six sub-basins used for environmental water management (see the Water management section for more information).

 

 

Figure C7 Total monthly flow for key rivers during the 2017–18 year compared with the average and percentiles

 

  • Streamflows were below average for most of the wet season, which reflects the relatively poor rainfall and soil moisture conditions experienced across the region during most of this period.
  • Streamflow in the Fitzroy, Nogoa and Comet rivers during February–March 2018 was less than expected given the high rainfall that occurred over the region in February. This is likely due to the relatively poor antecedent soil moisture conditions experienced in the upper reaches of these catchment areas.
  • Streamflow in the Isaac River during the entire wet season was well below average, particularly during February–March 2018. This is likely due to less rainfall occurring over the upper reaches of this catchment area during February 2018 than the central and southern parts of the region.