Drift quality classes simulated in ALGEQUEAU are transported from upstream to downstream, and the input concentrations are therefore needed.
Furthermore, the distribution at a node can be heterogeneous and requires the definition of a distribution coefficient. All these parameters can be set in through the boundary conditions window, accessible through the button or the Tools > Boundary conditions menu.

The first drop-down menu allows to choose on which type of network element we want to intervene :

• Reaches : k on upstream and downstream (in case of flow-inversion) ;
• Cross-structures : k ;
• Node : k for infiltration in the pond ;
• offtake : input (= boundary condition) for inflow and k for outflow.

The second menu allows the user to choose the element, and the third is for the quality class.

The user can then set the required parameters at the bottom of the window.

Distribution coefficients k may be adjustable in order to ensure mass conservation.