Reservoir inflow/outflow mapping difference in KW and LI routing

[atsiokanos]

Wflow version checks

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• I have checked that this bug exists on the latest version of Wflow.

Reproducible Example

NA

Current behaviour

It seems that the parameter "lateral.river.q_av" mapped at the reservoir locations ("wflow_reservoirlocs") represents inflows in kinematic wave models (identical to "lateral.river.reservoir.inflow") and outflows in local inertial (2d) model (identical to "lateral.river.reservoir.totaloutflow")

Desired behaviour

Keep them consistent or document the differences.

Additional Context

No response

[verseve]

This is not a bug, but caused by a difference in routing concept (local inertial vs. kinematic wave). For the kinematic wave we decided to solve river flow up to and including the reservoir location, which is more accurate for relatively small reservoirs. For the local inertial routing, reservoir locations are handled as boundary conditions: with a fixed h for the reservoir location (node) and reservoir outflow is copied to the downstream edge of that node.

It is not recommended to use q_av for the computation of reservoir inflow, because reservoir inflow also consists of overland and lateral subsurface flow.

Good suggestion to document this!