Inlet formula (Water Overlay)

Inlets are hydraulic structures that 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.

Case 1: Inlet:
When calculating Inlets, first the capacities are calculated.

If a lower threshold $T_{l, t}$ is defined:

Q_{l t h} = A \cdot m a x (0, T_{l, t} - w_{t})

If a positive inlet $q_{t}$ is defined:

Q_{p} = Δ t \cdot q_{t}

If a capacity $Q_{t o t a l}$ is defined:

Q_{c} = Q_{t o t a l} - \sum_{0.. t - 1} Q_{i}

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

Δ w = \frac{m a x (0, m i n (Q_{l t h}, Q_{p}, Q_{c}))}{A}

Case 2: Outlets:
When calculating outlets, first the capacities are calculated.

If an upper threshold $T_{u, t}$ is defined:

Q_{u t h} = A \cdot m i n (0, T_{u, t} - w_{t})

If a negative inlet $q_{t}$ is defined:

Q_{p} = Δ t \cdot q_{t}

If a capacity $Q_{t o t a l}$ is defined:

Q_{c} = - Q_{t o t a l} - \sum_{0.. t - 1} Q_{i}

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

Δ w = \frac{m i n (0, m a x (Q_{u t h}, Q_{p}, Q_{c}))}{A}

Where:

$Q_{0.. n}$ = The calculated previous amounts of flow.
$Q_{l t h}$ = The volume of water needed to reach the LOWER_THRESHOLD at the Inlet's location.
$Q_{u t h}$ = The volume of water that must be removed to reach the UPPER_THRESHOLD at the outlet's location.
$Q_{p}$ = The amount of water inflow (or outflow when negative) possible based on the INLET_Q of the Inlet and timestep $Δ t$ .
$Q_{c}$ = The total amount of water inflow (or outflow when negative) allowed based on the total capacity of the Inlet.

$A$ = Size of the Inlet/outlet area in m², based on the number of cells and cell size (currently calculated per cell).
$Δ w$ = The amount of water flow which takes place.

The following topics are related to this formula.