Attributes:

VKST [m^1/3 /s] (Manning-Strickler coefficient) (node-wise),

VBRT [m] (wetted perimeter) (node-wise)

VGRD [‰] (bottom slope) (node-wise),

VKNO [m³/TU] (inflow at a watercourse node) (node-wise),

VINZ [-], incidences of the edges defining the watercourse

VSYS [-], incidences of the watercourse systems (horizontal and 3D models only)

SPRING can automatically estimate the water level elevations in watercourses during flow simulations (steady-state and transient).

For this purpose, the individual watercourse sections or the entire meshed watercourse system needs to be parameterised with the wetted perimeter (VBRT), the bottom slope (VGRD) and the Manning-Strickler coefficient (VKST). These three parameters are required to calculate the water level elevations in the watercourses. These attributes each relate to the edges of elements.

The parameter VKNO defines an additional inflow at nodes of a water system. It is taken into account when calculating the flow rate, using the same time unit that is specified in the model file. The VKNO can be defined as a transient boundary condition as well.

The water systems are saved in the same way as 1D fracture systems. The VINZ attribute is used to create an incidence table for the affected edges of the elements, which in turn are grouped into watercourse systems using the VSYS attribute. Attributes are assigned to element edges, i.e. for the 1D elements stored in VINZ.

Where watercourses diverge, the water volumes are automatically divided into equal proportions in the direction of flow. Alternatively, the proportions can be defined by the user in the file sitra_vsys.txt .