Practice note: Data Requirements for Modelling Reach Losses

This practice note is one of a set developed to provide consistency and transparency of river system models being used within the Murray-Darling Basin. The notes cover modelling practices, such as naming conventions for folder structures, to model methods, such as for flow routing and residual inflow estimation, and have been developed through a collaboration between the MDBA, Basin States and CSIRO.

Produced in collaboration with:

This practice note, 'Data requirements for modelling reach losses', describes agreed general principles and recommended practices for sourcing of data to model known reach losses in eWater Source river system models; and provides examples of implementing the practices.

Background

Explicit reach losses include net evaporation, transmission losses associated with filling dead storage following an extended dry period, breakout to effluents and losses to wetlands, and groundwater–surface water exchanges. All or some of these known losses should be included during flow calibration.

A Practice note covering the modelling of transmission losses is also under development. The Source User Guide provides information on modelling Lateral reach losses (and Gains) at Lateral Losses and Gains.

Less experienced modellers should consult with more experienced modellers about how data have been obtained in the past.

General principles

The importance of the following known losses in the water balance should be considered for each reach model:
1. Seepage
2. Net evaporation
3. Losses to filling dead storage following extended dry periods
4. Breakouts to effluents and losses to wetlands
5. Surface and groundwater exchange.
At a minimum, the data required to model net evaporation should be obtained or estimated.
Where other losses are considered important, an effort should be made to obtain the data required to model the losses explicitly.
Significant known losses should not be included in the lumped loss relationships for a reach.

Recommended data requirements

Table 1: Loss type and recommended data requirements

Loss type	Data required to model losses
Seepage losses	Soil type and associated seepage rates
Net evaporation	Rainfall and evaporation (See Climate Data Practice Note) Rating curve (see Link rating curve section of Storage routing for rating curve. Estimate for surface area for different river flows Reach length
Initial loss following extended dry periods (Loss to dead storage)	Information about level, volume, area relationships Flow data for events following extended dry periods
Losses to floodplains and wetlands	Information from knowledgeable locals - location of breakouts and returns gauged flow data (see Flow Data practice note) cross-sections existing hydraulic models

Loss type	Data required to model losses
Losses to groundwater	Advice from groundwater experts Outputs from groundwater models

Background

General principles

Recommended data requirements

Companion Practice Notes

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