SWMM 4 and SWMM 5 St. Venant Solutions Contrasted
1. Compute at time t+delta t the values of dQ/dt for the Links and dH/dt for the Nodes from the properties at time t
2 Iterate at least 2 times until either all nodes and links are converged or a maximum of 8 iterations are reached
3. Use the values of Q and H at time t+delta t for the new time step
The SWMM5 Solution for Flow and Depth at each time step. The new depth and new flow is always based on the old depth and old flow and normally converges fast as the flow is gradually varied. The solution is iterative and implicitly uses the new depth and flow at each iteration.
The SWMM4 Solution for Flow and Depth is solved Explicitly at each time step. The new depth and new flow is always based on the old depth and old flow and and a half and full time step during the time step.