Boundary conditions must be established at all of the open ends of the river system being modeled. Upstream ends of a river system can be modeled with the following types of boundary conditions: flow hydrograph (most common upstream boundary condition); stage hydrograph; flow and stage hydrograph. Downstream ends of the river system can be modeled with the following types of boundary conditions: rating curve, normal depth (Manning's equation); stage hydrograph; flow hydrograph; stage and flow hydrograph.
Boundary conditions can also be established at internal locations within the river system. The user can specify the following types of boundary conditions at internal cross sections: lateral inflow hydrograph; uniform lateral inflow hydrograph; groundwater interflow; and Internal Stage and flow hydrograph. Additionally, any gated structures that are defined within the system (inline, lateral, or between storage areas and/or 2D flow areas) could have the following types of boundary conditions in order to control the gates: time series of gate openings; elevation controlled gate; navigation dam; Rules; or internal observed stage and flow.