9.4 Runoff to surface water
The volume reported (286,463 ML) represents runoff from the landscape into rivers and storages in the Adelaide region during the 2012–13 year.
Bureau of Meteorology: National Climate Centre daily climate grids (rainfall, temperature and solar radiation), Australian Hydrological Geospatial Fabric (AHGF) waterbody feature class; CSIRO: Australian Water Resources Assessment system Landscape model version 3.0 (AWRA-L) model parameters; South Australian Department of Environment, Water and Natural Resources (DEWNR): Geographic Information System layers.
Runoff to surface water was estimated based on the AWRA-L version 3.0 (Van Dijk 2010) model output and a water balance algorithm written by the Bureau of Meteorology.
Using climate grid data for the Adelaide region (including precipitation, temperature and solar radiation data), AWRA-L was used to estimate the runoff depth at each grid-point within the region. Only runoff from the landscape was considered; therefore, the surface areas of the major storages and the off-channel water storages (local catchment reservoir, e.g., farm dams) were excluded from the analysis.
Runoff from the landscape is divided into two components: runoff into the surface water (surface water storages and weirs, rivers and drains) and runoff into off-channel water storages. Only runoff into the surface water store was considered here because for the National Water Account; off-channel water storages are not included in the definition of surface water.
The average runoff depth from the landscape into surface water was determined as the weighted mean of the relevant grid-points within the region boundary. Points were weighted based upon the area they represented within the reporting region to remove edge effects (where the area represented is not wholly within the reporting region) and the effect of changing area represented with changing latitude. Runoff depth was converted to a runoff volume by multiplying runoff depth by the total area of the region (excluding surface water storages, weirs and off-channel storages) and was used as input to the into the water balance algorithm.
Assumptions, limitations, caveats and approximations
- Runoff estimates were compared to flows at unimpaired catchments within the Adelaide region for the 2012–13 year and found to be a reasonable representation of the runoff in this region for this year
- Runoff estimates were subject to the assumptions of the AWRA-L model detailed by Van Dijk (2010).
The comparative year volume for line item '9.4 Runoff to surface water' was restated in the water accounting statements from the 2012 Account due to an error identified in the method used to calculate this volume. Please refer to Restatement of comparative year information in the 'Water accounting policies' for more information.