Definitions for "Boundary conditions"
Conditions (usually justified by no-arbitrage arguments) that are imposed on the boundary of the domain where the solution of a differential equation is sought. Natural conditions are usually imposed through a surface term after partial integration; essential conditions are imposed explicitly in the linear system by replacing an equation by the condition.
The stage, discharge, or rating curve data needed at one or more terminating branches of an unsteady-flow model in order to solve the equations of flow for the system.
Hydraulic head or mass/heat-transport, flux, transfer and well conditioning values along sections and on single nodes. Along the spatial boundaries of the model the flux boundary is set 0 as default. The boundary is therefore impermeable.
The means of specifying the forcing at boundaries of numerical models (Section 8.2.6)