You can change between the Backward Euler reservoir routing methods (default) and the Piecewise-linear Integral in Scenario Options » Storages.
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- The solution technique used assumes inflows, loss and gain fluxes, and outflows are averaged over a model time-step. This is consistent with the approach used in other parts of Source, such as link routing;
- The storage reservoir is assumed to have a level pool; and
- Relationships between storage water level, volume, surface area, and outflows are defined in terms of piecewise linear, monotonically increasing coordinate sets.
Theory
Approach of Backwards Euler
Source uses an implicit (backward) Eulerian approach for link storage routing. It assumes that the flux averages over a time step are a function of the state at the end of the time step:
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Table 1. Example of pre-computed solution table
These values stay the same for the length of the model run and can then be used at each time step. Using the current value of Ordersj and Edepth we can calculate the corresponding value of ε for each table row (V):
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