26.1 Soil moisture
This line item represents the volume of water held within the soil profile across the whole of the Canberra region. The volume reported for the 2011 Account was 714,289 ML.
Soil moisture for the Canberra region was estimated based on the AWRA-L version 1.0.0 (Van Dijk, 2010) surface soil, shallow soil and deep-soil moisture model outputs.
Using climate grid data for the Canberra region (including precipitation, temperature and solar radiation data), AWRA-L was used to estimate the soil moisture for each soil layer at each gridpoint within the region. Only soil moisture within the landscape is considered; therefore, the surface areas of the major reservoirs were excluded from the analysis.
The total depth water in all three layers of the soil column at each grid point was extracted. This depth was then multiplied by the surface area represented by each individual grid point to give a volumetric estimate for every grid point. The volume for each grid point was summed up to provide an estimate of soil moisture for the entire Canberra landscape.
Assumptions, Limitations, Caveats and Approximations
- These estimates have not been compared to any real-time measured data for the 2010–11 reporting year.
- The soil moisture estimates are subject to the assumptions of the AWRA-L v1.0.0 model detailed in Van Dijk (2010).
- AWRA-L was balanced according to the supply of water to the landscape via precipitation and therefore does not account for application of water via irrigation and lateral flow.
The uncertainty estimate was not quantified.