Water Balance Tool

The Hydrometric Network and Remote Sensing (HNRS) program was established by the  Commonwealth Department of Climate Change, Energy, Environment and Water to increase the amount and quality of publicly available information about water in the Northern Murray Darling Basin. A HNRS workstream produced a water balance tool that provides up-to-date information on water gains and losses at a reach and catchment scale.

Water balance is a common approach in hydrology based on mass balance principles. This means that the sum of inflows, outflows and changes in water stored must balance over a given time step.

The visualisation tool is populated with observed and modelled outputs and is updated daily. The water balance tool has been rolled out to the Namoi and Murrumbidgee regulated rivers. Roll out to additional river systems is planned subject to funding and resource availability.

• The data on the visualisation is updated daily. Data gaps are filled using estimates and/or previous forecasts.
• There is uncertainty regarding the high flow readings above the channel capacity.
• The reach entitlement volume displayed on charts and tables represents the maximum potential entitlement volume in the reach. The entitlement held on an access licence is available for extraction via all linked work approvals, which can be located across multiple reaches. The volume extracted via a work approval will vary each year depending on climate, seasons, allocation and cropping patterns.
• The extraction volume is showing the licenced extraction from the reach and may include environmental water that is not extracted. Until more information is available on how Held Environmental Water is to be used, it has been modelled as a consumptive use.
• Data sourced from external database may be revised and/or corrected over time.
• For some reaches, it is not possible to develop reliable estimates or calculation of the water balance component volume e.g. losses, ungauged inflows. When this situation occurs, the volume of the component contributes to the unaccounted difference in reach.
• A comprehensive analysis on water availability, allocations, usage, trade and delivery is provided in the department's annual General Purpose Water Accounting Report for the NSW regulated water sources.

Namoi Catchment

• Reach 13 (Goangra (419026) to Walgett (419091)) downstream gauge only provides level information and no discharge.  Reach 15 (Downstream Pian Cutting (419079) to Hazeldene) does not have a measured downstream gauge to compare against the modelled flows. Therefore, both reaches have been excluded in the water balance tool.

Murrumbidgee Catchment

• The Wagga Wagga to Narrandera river section is modelled as a single reach in the DCCEEW planning model. For the water balance tool this section has been split into Reach 04 (Wagga Wagga to Berembed weir) and Reach 05 (Berembed weir to Narrandera). Losses for the section have been assigned to Reach 05 in the reach water balance tool as most of the loss occurs from Reach 05.
• In Reach 4 where water is extracted from the river for Murrumbidgee Irrigation (Main canal), and Reach 6 where water is extracted for Coleambally Irrigation (Coleambally canal) and Murrumbidgee Irrigation (Sturt canal), these volumes are captured as gauged outflows from the reaches not licence extractions.

Lowbidgee

• During high flow events there are significant outflows from the Murrumbidgee river to the Lowbidgee flood plain, area which is a major environmental asset in the Murray Darling Basin. Inflows to Lowbidgee are through controlled offtakes (gauged outflows) or high flow breakouts (ungauged outflows). Discrete network models of the Lowbidgee flood plain have been extracted from the Murrumbidgee planning model. These network models estimate flood plain storage volumes and return flows to the Murrumbidgee river.