Inlet formula (Water Overlay)

The amount flowing in or out of inlets is calculated for the cell the inlet resides on.

When calculating inlets, first the capacities are calculated.

If a T_lower is defined:

C_inthres = max( 0 , T_lower - WL_surface )

If a I_Q is defined:

C_speed = Δt * I_Q

If a C_total is defined:

C_incap = C_used - C_total

After calculating the capacities, the actual water inflow is calculated.

Δw = max( 0 , min( C_inthres , C_speed , C_incap ) ) / cell

If any of the terms are undefined, they are not included.

When calculating outlets, first the capacities are calculated.

If a T_lower is defined:

C_outthres = min( 0 , T_upper - WL_surface )

If a I_Q is defined:

C_speed = Δt * I_Q

If a C_total is defined:

C_outcap = -C_total - C_used

After calculating the capacities, the actual water ouflow is calculated.

Δw = min( 0 , max( C_outthres , C_speed , C_outcap) ) / cell

If any of the terms are undefined, they are not included.

After the water flow (either inflow or outflow) is computed, the capacity is updated.

C_used (new) = C_used (old) + (Δw * cell)

Where:

• Δw = The amount of water flow which takes place.
• Δt = Computational timestep.
• cell = Cell size.

• C_speed = The amount of water inflow (or outflow when negative) possible based on the inlet's INLET_Q attribute.
• C_incap = The amount of water inflow possible based on the total capacity of the inlet.
• C_outcap = The amount of water outflow possible based on the total capacity of the outlet.
• C_inthres = The amount of water inflow desired based on the inlet's LOWER_THRESHOLD attribute.
• C_outthres = The amount of water outflow desired based on the outlet's UPPER_THRESHOLD attribute.

• WL_surface The water level on the surface, relative to datum.
• C_total = The INLET_CAPACITY attribute of the inlet.
• I_Q = The INLET_Q attribute of the inlet.
• T_lower = The LOWER_THRESHOLD attribute of the inlet.
• T_upper = The UPPER_THRESHOLD attribute of the inlet.