Daly
9.4 Runoff to surface water

The volume recognised in the water accounting statements of 7,131,000 ML represents the total volume of runoff into surface water within the Daly region during the 2012–13 year.

The large difference that is observed between the 2011–12 volume and the 2012–13 volume can be attributed to the difference in weather patterns experienced between the wet seasons. The 2011–12 year rainfall was average to above average (see Climate overview from the 2012 Account). The rainfall patterns observed in this season was characterised by monsoonal rainfall throughout much of the season. These heavy periods of rain caused rapid movement of water through the catchment. The 2012–13 wet season exhibited a very different pattern. The wet season as a whole recorded an average rainfall, but this was characterised by long dry periods interspersed with short, wet bursts. These rainfall patterns limited the amount of water movement and resulted in much less recharge and discharge.

Runoff to surface water in the Daly region was estimated using a surface water model of the Daly River catchment developed using the MIKE 11 software by DHI.

The calibration of the MIKE 11 model involved adjusting the model parameters to ensure model outputs matched observed streamflow data in the region adequately. A detailed description of the model calibration process is provided in NRETAS 2010.

The runoff estimates were subject to the assumptions of the MIKE 11 model detailed by NRETAS 2010.

Derived from modelled data. The uncertainty estimate was not quantified.