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A Simple River model engine was developed as an example of model migration. The model engine is programmed in Fortran and is a very simple conceptual river model. The Simple River consists of nodes and branches, as shown in Figure 4-41. For each timestep, the inflow to each node is obtained from a boundary-input file. These flow rates are multiplied by the timestep length and added to the storage in each node. Then, starting from the upstream end, the water is moved to downstream nodes and the flow rate in each branch is calculated.
Fig 1. Simple River network
The Simple River engine reads data from three input files, which contain information about the inflow to the river nodes (boundary file), the simulation period and timestep length (simulation file) and the river network (network file) - see Figure 2.