Bureau Home » Water Information » National Water Account » 2017 Account » Fitzroy » Reference information » Methods

National Water Account 2017

Fitzroy: Methods

Carnarvon Gorge (© Greg Keir)

Summary of methods

Table N3 outlines the methods used to derive the item volumes for the Fitzroy region. For a more detailed description of the quantification approach, click on the relevant item name in the table.

 

Table N3 Methods used to derive item volumes

Assets
Approach or data used Item Source
Water storage product data Bureau of Meteorology
  SunWater
  AWRA-R model
Not quantified
  • Underlying aquifers
 

 

Liabilities
Approach or data used Item Source
Water resourcing licence database and meter readings SunWater and Department of Natural Resources, Mines and Energy

 

Inflows and outflows
Approach Item Source
AWRA-L model Bureau of Meteorology
AWRA-R model Bureau of Meteorology
Gridded climate data Bureau of Meteorology
Not quantified
  • Recharge; landscape
  • Discharge: landscape
  • Other; statutory rights
  • Inter-region inflow
  • Inter-region outflow
 

 

Abstractions
Approach or data used Item Source
Water resourcing licence database and meter readings SunWater and Queensland Department of Natural Resources, Mines and Energy

 

Detail of methods

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 volume of individual storages was aggregated to present the total volume for the line item as detailed in the supporting information table. The uncertainty range for the storage volume 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, which in turn affect the accuracy of the storage–volume curves.

 

Water table aquifer

The water in the aquifers is assumed to equal the total entitled maximum volume extractable from the Callide Valley water supply scheme.



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 River network used in AWRA-R model for Fitzroy region 

Figure N1 River network used in AWRA-R model for Fitzroy region

 

Further detail on the AWRA-R model and description of its assumptions can be found in Dutta et al. (2015) and Dutta et al. (2017).

 

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).

 

Rivers

The volume of water in the river channels at 30 June was estimated by using the daily water balance approach within AWRA-R. The water balance includes inflow at the upstream nodes and outflow at the downstream nodes; contributing catchment runoff, reservoir contribution, irrigation diversion and return; overbank flooding and floodplain return; loss to groundwater; anabranch flow; rainfall; and evaporation.

 

Gridded climate data

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 for rivers were carried out on a daily time step using the AWRA-R model. Calculations for storages were done on a monthly time step. Annual totals were summed from the daily or monthly 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). 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.

 

Runoff

Runoff to surface water was estimated based on the AWRA–L version 5.0 (Viney et al. 2015) model outputs. Runoff areas to storages, gauged area and modelled area are shown in Figure N2.

 

Figure N2 Runoff from gauged area and modelled area within the Fitzroy region
Figure N2 Runoff from gauged area and modelled area within the Fitzroy region
 

 

Using gridded climate data for the Fitzroy region (including precipitation, temperature and solar radiation data), the AWRA–L model was used to estimate the runoff depth at each grid cell within the region. Only runoff from the landscape was considered; therefore, the surface areas of the major reservoirs were excluded from the analysis.

The average runoff depth from the landscape into the connected surface water store was determined as the weighted mean of the relevant grid cells within the region boundary. Cells 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 storages).

The approach was subject to the assumptions of the AWRA–L model (detailed in Viney et al. 2015).

 

Water resourcing licence database and meter readings 

Allocation remaining

The water management year commences on the date the licence is issued. In most cases, particularly for individual users, the licence anniversary falls outside the standard water year (1 July–30 June). As a result, the water allocation remaining at the end of the 2016–17 year is the unused component of the annual allocation for the licence. The allocation remaining at 30 June 2017 is calculated as shown in Table N4.

 

Table N4 Calculation of water allocation remaining
  Account
  Opening balance at 1 July 2016
add Allocation
less Allocated abstraction
less Adjustment and forfeiture
equals Closing balance at 30 June 2017


Adjustment and forfeiture

The portion of groundwater allocation that has not been abstracted at the end of the licence water year is 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. Individual user entitlements that are terminated during the year are also considered to be forfeitures. Remaining surface water allocation for individual users and irrigation are carried over.

 

Allocation

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 rights, entitlements, allocations and restrictions note.

 

Allocation diversion: individual users

The entitled diversion of allocated water by individual users during the licenced water year is derived from volumetric charging (metered data).

The expected error associated with metered data 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. The uncertainty of the estimated data is unquantified.

 

Allocated diversion: urban system

The entitled diversion of allocated water for the urban water system during the licensed water year is based on measured 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 diversion: irrigation

Most of the entitled diversion of allocated surface water in the Fitzroy region is for irrigation scheme water supply. The entitled diversion of allocated water for Irrigation concentrates in the Dawson and Nogoa Mackenzie water supply schemes. 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.

 

Allocation extraction: individual users

The entitled extraction of allocated water by individual users during the licenced water year is derived from volumetric charging (metered data).

The expected error associated with metered data 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. The uncertainty of the estimated data is unquantified.

 

Allocated extraction: urban system

The entitled extraction of allocated water for the urban water system during the licensed water year is derived from volumetric charging (metered data).

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 extraction: irrigation

Most of the entitled extraction of allocated groundwater in the Fitzroy region is for irrigation scheme water supply. The entitled extraction of allocated water for Irrigation concentrates in the Dawson and Nogoa Mackenzie water supply schemes.

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.

 

Non-allocated diversion: individual users

The 'non-allocated diversion: individual users' volume is calculated from the volume of surface water diverted (metered at the source) or estimated.

The estimated uncertainty of this volume was +/– 20%.

 

Non-allocated extraction: individual users

The 'non-allocated extraction: individual users' volume is calculated from the volume of groundwater extracted (metered at the source) or estimated.

The estimated uncertainty of this volume was +/– 20%.