Burdekin
Quantification approaches
Summary of quantification approaches
Table 1 outlines the quantification approaches used to derive the item volumes for the Burdekin region. For a more detailed description of the quantification approach, click on the relevant item name in the table.
Detail of quantification approaches
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. Rating 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 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, which in turn affects the accuracy of the storage–volume curves.
Stream monitoring data
River outflow from the region
The total volume of river outflow to sea is the sum of the available flow data from the following guaging stations (Figure 1):
- Burdekin River (Clare): 120006B
- Haughton River: 119003A
- Barratta Creek (Northcote): 119101A.
Figure 1 Gauging stations used to calculate total outflow to sea
The river outflow was estimated using instantaneous discharge data (L/s) collected at the most downstream gauging station (nearest to the outlet to the sea) along a river. These data were converted to daily volume data (ML) to determine the total annual discharge (in ML) at each station during the year.
It is assumed that the river outflow to the sea is equal to the volume of discharge measured at the most downstream station along a river, that is, there is no adjustment made for the contributing area below the gauging station used to calculate the outflow.
The Department of Natural Resources and Mines assign quality codes to flow data in accordance with Table 2.
| Quality code | Description |
| 9 | normal reading |
| 20 | fair |
| 30 | poor |
| 59 | derived height |
| 60 | estimated |
| 160 | suspect |
| 200 | water level below threshold |
| 255 | no data exists |
The total volume of water that outflows into the sea from Burdekin River, Haughton River and Barratta Creek has a quality code of 60(estimated). The overall quality code represents the lowest data quality rating assigned to a monthly flow record during the 2013–14 year.
Climate grid data
Precipitation and evaporation on/from surface water
Monthly precipitation grids for the region were produced using daily data from approximately 6,500 rain gauge stations and interpolated to a 0.05 degrees (5 km) national grid (Jones et al. 2007).
Potential evaporation across the region was estimated using the Australian Water Resources Assessment system Landscape model (AWRA-L) version 3.0 (Van Dijk 2010). The AWRA-L model uses a modified version of the Penman-Monteith method to produce the potential evaporation. Daily AWRA-L potential evaporation grids for the region were produced based on daily gridded climate data (including precipitation, solar radiance and temperature) that were available on a 0.05 degree (approximately 5 km) national grid (Jones et al. 2007).
The precipitation and evaporation at each waterbody was estimated from the proportionally weighted average of grid-cells that intersected each water feature. The volume was then estimated by multiplying by the surface area of each waterbody. The average monthly surface area of the storages was calculated from daily storage levels and capacity tables where data were available. Where daily storage level data were unavailable, a static surface area value from the Australian Hydrological Geospatial Fabric was used.
The limitations associated with this approach are:
- The dynamic storage surface areas calculated from the levels and capacity tables represent a monthly average and therefore will not capture changes that occur on a shorter temporal scale.
- Dynamic storage surface area data are not available for five storages. Therefore, the Australian Hydrological Geospatial Fabric surface water feature was used to estimate a static surface area for these storages. This represents the storage at total capacity and, therefore, likely results in an over-estimation of precipitation and evaporation at the storage.
- The total surface area of the surface water store within the Burdekin region included only the storages (and not the rivers).
Another pertinent point to mention (in the context of the pilot account) is that the evaporation and precipitation values calculated, did not take in to account a 19,700 ML portion of the total volume. This volume represents the aggregated storage capacities of Blue Valley Weir, Bowen River Weir, Gorge Weir, Val Bird Weir and Charters Towers Weir. This accounts for less than 1% of the total storage capacity therefore the evaporation and precipitation values calculated for this pilot stage account can be regarded as slightly conservative. Subsequent account releases will be adjusted to account for these storages.
Runoff to surface water
Runoff to surface water in the Burdekin region was based on a combination of observed streamflow data and streamflow estimates from the AWRA-L model outputs.
The volume of runoff in the catchment area upstream of Lake Dalrymple (approximately 85% of the Burdekin region area) was estimated based on observed streamflow data. The runoff is assumed to equal the sum of flow data from guaging stations along the three primary rivers that flow into Lake Dalrymple (see Figure 7 in the 'Contextual information'):
- Burdekin River: 120002C
- Cape River: 120302B
- Suttor River: 120303A.
The runoff in the remaining 15% of the region was based on AWRA-L model outputs. Using climate grid data for the Burdekin region (including precipitation, temperature and solar radiation data), AWRA-L model was used to estimate the runoff depth at each grid point within the 'ungauged' portion of the region. Only runoff from the landscape was considered; therefore, the surface areas of the storages 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 points within the region boundary. Points were weighted based upon the area they represented within the 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 modelled region (excluding storages).
The estimated runoff was compared against historical flows at unimpaired catchments within the Burdekin region for the 2013–14 water year and provided a suitable representation of the runoff for this year.
The approach was subject to the assumptions of the AWRA-L model detailed in Van Dijk 2010.
Water resourcing licence database and annual reports/meter readings
Water 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 2013–14 year is the unused component of the annual allocation for the licence. The allocation remaining at 30 June 2014 is calculated as shown in Table 3.
| Account | |
| Opening balance (at 1 July 2013) | |
| add | Allocation announcement |
| less | Entitled abstraction of allocated water |
| less | Adjustment and forfeiture |
| equals | Closing balance (at 30 June 2014) |
Adjustment and forfeitures of water allocation
The portion of water allocation that has not been abstracted at the end of the licence water year is forfeited (i.e. there is no carry-over 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.
Water allocation announcements
Water licences are generally issued for periods of between five and ten years, 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 (usually 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.
Entitled abstraction of allocated water to individual users
The entitled abstraction of allocated water by individual users (both surface water and groundwater) 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. For estimated data the uncertainty is unquantified.
Entitled abstraction of allocated water to urban water system
The entitled abstraction of allocated water for the urban water system (via the Bowen Broken Water Supply Scheme) 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.
Entitled diversion of allocated surface water to irrigation scheme
Most of the entitled diversion of allocated surface water in the Burdekin region is for irrigation scheme water supply. The entitled diversion of allocated water for Irrigation combines total report volumes from the Bowen Broken and Burdekin Haughton 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.
Point return from irrigation scheme
Point return from the irrigation scheme has been assigned (– ML) indicating that it failed the recognition criteria as based on the information available it could not be quantified in a way that is complete, neutral and free from material error.
Transfer of water outside of region
The inter-region licence relates to water transferred from the Paluma and Burdekin Haughton storages to the headwaters of Crystal Creek and Ross River respectively; both of which are located outside the Burdekin region boundary.
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.