Daly: Climate and water
Several strong monsoon troughs over northern Australia contributed to above-average annual rainfall in the region, particularly during December–February, the typically wetter months of the year. The high rainfall during this period contributed to above average streamflows across the region.
For further information on the region's climate and water conditions during the 2016–17 year scroll down this page or click on the links below:
About the region
The Daly region lies within the wet–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.
Although the majority of the annual flow in the region's rivers occurs during the wet season, the Daly River system is one of the few in northern Australia to have perennial flow. The dry-season flow (May–October) is mostly dominated by input of groundwater from the two underlying limestone aquifers, Tindall and Oolloo.
Climate conditions
Rainfall
Figure C1 Annual and monthly rainfall deciles for the Daly region during the 2016–17 year
- Several monsoon troughs over northern Australia during December–February, typically the wetter months of the year, contributed to above-average annual rainfall across the region.
- Total area-averaged rainfall for the year was 1,360 mm, which was higher than the mean annual rainfall of 1,000 mm.
Figure C2 Total monthly rainfall for the Daly region during the 2016–17 year compared with the long-term average and percentiles for the region
- Rainfall was above average for almost the entire wet season (November–April).
- January rainfall was above the 90th percentile for that month due to heavy rainfall associated with a tropical low that impacted the region in late-January.
Evapotranspiration
Figure C3 Annual and monthly actual evapotranspiration deciles for the Daly region during the 2016–17 year
- Total area-averaged actual evapotranspiration was 914 mm, higher than the mean value of 801 mm.
- The above-average evapotranspiration may be attributed to a combination of above-average temperatures across the region and increased water availability due to the high rainfall during the year.
Figure C4 Total monthly evapotranspiration for the Daly region during the 2016–17 year compared with the long-term average and percentiles for the region
- Actual evapotranspiration was above average for almost the entire year.
Soil moisture
Figure C5 Annual and monthly soil moisture deciles for the Daly region during the 2016–17 year
- Soil moisture in the root zone (0–1 m depth) was above average across the entire region.
- Rainfall and soil moisture are typically closely aligned. For example, above-average soil moisture during January–March 2017 reflects the above-average rainfall that occurred during the typically wetter months of the year (December–February).
- More information on soil moisture distribution across the Daly region is available in the Australian Landscape Water Balance.
Streamflow responses
Streamflow
Figure C6 Key flow gauging stations along the main rivers within the Daly region
- The Katherine and Daly rivers are two primary rivers within the Daly region.
Figure C7 Total monthly flow for major rivers in the Daly region during the 2016–17 year compared with long-term average and percentiles
- Total annual flows in the Katherine and Daly rivers were more than 25% above the mean annual flow, and greater than the annual flow last year.
- The combination of above-average rainfall and soil moisture conditions experienced during the typically wetter months of the year (December–February) resulted in well above-average streamflows during this 3-month period.