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

1. 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.
2. At a minimum, the data required to model net evaporation should be obtained or estimated.
3. Where other losses are considered important, an effort should be made to obtain the data required to model the losses explicitly.
4. 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

Companion Practice Notes

• Practice note: Selecting climate data
• Practice note: Selecting flow data