Burdekin: Methods
Summary of methods
There were four key methods for establishing item volumes in the 2019 Account. Click the down arrow in the table below to view the list of items derived by each method type. For detailed information about each method scroll down this page or click on the links in the table.
Methods approach
AWRA-R model
Water storage product data
Water resourcing licence database and meter readings
Operational Data Storage System
Detail of methods
AWRA-R model
AWRA-R is a river network model that represents key hydrological processes and diversions at a daily time step (Dutta et al. 2017; 2015). The model was used in the National Water Account to quantify river fluxes and stores along the river network.
The river system is conceptualised in AWRA-R as a node-link network comprising nodes connected by river reaches. Gauged streamflow data are used where available. For ungauged portions of catchment, the landscape runoff from the AWRA-L model is used (Viney et al. 2015). River processes represented in the AWRA-R model are shown in Figure N1.
Figure N1 Conceptual diagram of AWRA-R reach showing model components (from Dutta et al. 2015)
Rivers
The volume of water in the river channels at 30 June was estimated by using the daily water balance approach within the AWRA-R model. The water balance includes inflow at the upstream nodes and outflow at the downstream nodes; contributing catchment runoff, diversions for consumptive use; overbank flooding and floodplain return; rainfall; evaporation; and losses.
Precipitation and evaporation
Rainfall and evaporation into/from storages and rivers were calculated using climate data from the Bureau of Meteorology interpolated to 0.05 degree (5 km) national grids (Jones et al. 2009). Calculations were done on a daily time step, with the annual totals summed from the daily values.
Climate data for each water body at each time step were estimated from the proportionally weighted average of grid-cells that intersected the water body. Evaporation was estimated using Morton's shallow lake formulation (Morton 1983). Rainfall and evaporation volumes were then estimated by multiplying the surface area of each waterbody by the weighted average rainfall and evaporation respectively. The average daily surface area of rivers was estimated using the AWRA-R model and the average daily surface area of storages was calculated from daily storage levels and capacity tables.
Runoff
Runoff to surface water was estimated using the modelled runoff from the AWRA-R model. Runoff within AWRA-R is in turn derived from landscape runoff modelled in the AWRA-L model, with a scaling factor applied within AWRA-R during the calibration process.
The AWRA-L model is a daily grid-based water balance model that is conceptualised as a small unimpaired catchment (Viney et al. 2015). It simulates the flow of water through the landscape from rainfall entering the grid cell through the vegetation and soil, and then out of the grid cell through evapotranspiration, runoff or deep drainage to the groundwater. Its inputs include gridded climate, soil, vegetation and topographic data. For more information see the Bureau's Australian Landscape Water Balance webpage.
Outflow
River outflow is estimated with the AWRA-R model using dummy nodes assigned at the end of of each river flowing out of the region. Observed flows (or simulated flows if observed flow is not available) at the most downstream gauges are routed to the dummy nodes. The residual catchment inflows not covered by the most downstream gauge are estimated using the AWRA-L model and are added to the routed flow to obtain the total outflow at the river mouth.
Overbank flow and flood return
The AWRA-R floodplain module was used to model the volume of overbank flow from the river onto the floodplain, and the return flow from the floodplain back into the river. The module applies a simple storage-based floodplain model to each river reach. The floodplain modelling method is detailed in Dutta et al. (2013).
Water storage product data
Storages
Storage volume at the start and end of the year was calculated using water level data (metres above Australian Height Datum) collected at each storage. Capacity tables established for each storage were used to convert the height measurement to a volume. The uncertainty range for these volumes is +/–5%.
The assumptions made were as follows:
- Storage–volume curves represent specifically surveyed parts of the storage and may not reflect the storage–volume relationship across the entire storage.
- Storages are subject to sedimentation and other physical changes over time that in turn affect the accuracy of the storage–volume curves.
- No storage data were available for several of the region's smaller storages. Given the combined storage capacity in these small storages is less than 2% of the region's total storage capacity, not including these storages in the account made no material difference to the region's total storage volume.
Water resourcing licence database and annual reports/meter readings
Allocation remaining
The water allocation remaining for a water licence at the end of the reporting year is the unused component of the annual allocation. In some cases, the allocation remaining is carried over into the next year. This may apply to surface water allocations for individual users or irrigation schemes.
Where there is no carryover provisions for a water supply licence, the portion of water allocation that has not been abstracted at the end of the water year is forfeited. The allocation remaining at the end of the water year is 0 ML.
Adjustment and forfeiture
The portion of water allocation that has not been abstracted at the end of the licence water year is generally forfeited (i.e., there is no carryover of entitlements). Therefore, forfeiture is calculated as the total annual allocation for each licence minus the allocation abstraction during the licence water year.
In some cases, a portion of surface water allocation that has not been abstracted at the end of the licence water year may be carried over. This may apply to surface water allocations for individual users or irrigation schemes.
Allocations
Queensland water licences are issued with an annual abstraction amount specified and with annual compliance arrangements in place.
The maximum amount of abstraction under a water entitlement is announced by the resource operations licence holder on an annual basis. The announced allocation is made after a review of storage and aquifer levels in the region on the first day of the water year (1 July). Subsequent additional announcements may be made throughout the year if additional water becomes available.
More information on these allocations and the associated water access entitlement is given in the Water access and use note.
Allocated abstraction: individual users
The allocated abstraction of water by individual users during the licenced water year is derived from volumetric charging (metered data).
Where metered data are available, the water use is calculated as the actual abstraction during the year. The expected error associated with these diversions is +/– 5%. SunWater requires that all water meters, when tested under in situ conditions, must be within 5% accuracy across the full flow rate range.
Where metered data are not available the volume of abstraction is assumed to be the full annual entitlement. There is not sufficient information relating to actual abstraction to provide more accurate estimates of abstraction for all licences.
Allocated abstraction: urban system
The allocated abstraction of water for the urban water system during the licensed water year is based on metered data collected at the outlet of the water source using a cumulative water meter.
The expected error associated with these abstractions is +/– 5%. SunWater requires that all water meters, when tested under in situ conditions, must be within 5% accuracy across the full flow rate range.
Allocated abstraction: irrigation
The allocated abstraction of water for the irrigation schemes combines total report volumes from the Bowen Broken and Burdekin Haughton water supply schemes.
The expected error associated with these abstractions is +/– 5%. SunWater requires that all water meters, when tested under in situ conditions, must be within 5% accuracy across the full flow rate range.
Allocated abstraction: inter-region
The allocated abstraction of inter-region water combines total reported volumes pumped outside of the Burdekin water resource area boundary.
The expected error associated with these abstractions is +/– 5%.
Non-allocated abstraction: individual users
The non-allocated abstraction of water by individual users is calculated from the total volume of licenced entitlements and permits of users operating outside of the regions principal water supply schemes.
The expected error associated with these abstractions is +/– 5%.
Operational Data Storage System
Managed aquifer recharge
Lower Burdekin Water and the Department of Natural Resources and Mines manage the majority of the aquifers in the lower Burdekin delta. SunWater do not manage aquifer recharge (outside the Giru Benefited Area). The expected error associated with this reported volume is +/– 5% but only extends to surface water metering, not groundwater recharge.