Inlet formula (Water Overlay)

Inlets are hydraulic structures can pump water in and out of the project area and are connected with a water body outside the project area.

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

Inlets:
When calculating inlets, first the capacities are calculated.

If a lower threshold T_l is defined:

Q_lth = max( 0 , T_l,t - w_t )

If a positive Inlet q is defined:

Q_t = Δt * q_t

If a capacity Q_total is defined:

Q_c = Q_total- ΣQ_0..t-1

After calculating the capacities, the actual water inflow is calculated. If any of the terms are undefined, they are not included.

Δw = max( 0 , min( Q_lth , Q_t , Q_c ) ) / A

Outlets:
When calculating outlets, first the capacities are calculated.

If an upper threshold T_u is defined:

Q_uth = min( 0 , T_u - w_t )

If a negative Inlet q is defined:

Q_t = Δt * q_t

If a capacity Q_total is defined:

Q_c = -Q_total - ΣQ_0..t-1

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

Δw = min( 0 , max( Q_uth , Q_t , Q_c) ) / A

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.
A = area of the inlet/outlet
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.

See also