Source Node
The Source Node represents a point where water enters the network, functioning as either a head-driven hydraulic source or a flow-driven exogenous inflow.
Depending on your modeling goals, the Source Node can be switched between two distinct operating modes:
- Reservoir (Fixed Head / Water Elevation): A hydraulically driven boundary that maintains a fixed total head (water surface elevation). Flow is governed dynamically by downstream network resistance and can even reverse into the node if system pressures rise.
- Defined Inflow Rate (Flow Injection): A flow-driven exogenous supply that injects a predetermined flow rate ($Q$) directly into the system, regardless of network pressure.
Operating Modes & Hydraulic Behavior
1. Reservoir Mode (Hydraulically Driven)
In Reservoir Mode (synonymous with an EPANET Reservoir), the node establishes the Hydraulic Grade Line (HGL) at a fixed total head.
- How it Works: The node acts as an infinite water source (or sink). The rate of water entering the pipeline is not fixed; instead, it is determined dynamically by the hydraulic gradient, pipe headloss, and pump/valve operations downstream.
- Bi-directional Flow: While placed as a source, water can naturally reverse and flow into the reservoir if network pressures exceed the node's total head (for example, during a pump shut-off surge or high downstream storage).
- Common Real-World Equivalents:
- A large lake, river, or ocean intake.
- A connection to a large, high-capacity municipal supply main with known pressure.
- An open atmospheric forebay or large clearwell.
[!NOTE] In Reservoir Mode, the node does not have a finite volume or dynamic water level geometry like a Storage Tank. It represents an infinite boundary whose head remains constant unless modulated by a Head Pattern.
2. Defined Inflow Mode (Exogenous Flow Injection)
In Defined Inflow Mode (modeled from an EPANET perspective as a Junction with negative demand), the node forces a specified volumetric flow rate into the system.
- How it Works: The inflow rate is treated as an exogenous input. The specified volume of water enters the network every second regardless of the pressure head at the connection point.
- Canvas Interaction: When placed in Defined Inflow Mode, a live slider appears on hover in the modeling canvas, allowing you to manually dial the inflow rate up or down during interactive simulation runs.
- Common Real-World Equivalents:
- A deep well pump discharging a constant flow directly into a manifold.
- A metered tributary, river diversion, or upstream watershed inflow.
- An unmodeled upstream process plant delivering a scheduled flow sequence.
[!TIP] Use Defined Inflow Mode when you know the exact flow rate entering the system (e.g., from flow meter data) rather than the supply pressure.
UI Workflow and Configuration
To add a Source Node to your model: 1. Locate the Source Node icon (a circular node with wave glyphs) in the left toolbar. 2. Drag and drop the icon onto the canvas. 3. Right-click the node and select Properties (or double-click) to open the configuration dialog.
Configuration Fields
Source Mode Selection
At the top of the Properties dialog, select your desired Source Mode:
- Defined Inflow Rate (Flow Injection)
- Reservoir (Fixed Head / Water Elevation)
Fields in Reservoir Mode
| Field | Description |
|---|---|
| Component ID | Unique identifier for the node (e.g., Source_1, Lake_Intake). |
| Total Head | The total baseline hydraulic grade line (elevation + pressure head), measured in feet or meters. |
| Head Pattern | Optional diurnal or seasonal multiplier pattern applied to Total Head (e.g., simulating tidal shifts, seasonal drawdown, or diurnal grid pressure swings). |
| Water Quality | Baseline chemical concentration (e.g., Chlorine mg/L), source water age (hours), or constituent percentage for tracking water propagation through the network. |
Fields in Defined Inflow Mode
| Field | Description |
|---|---|
| Component ID | Unique identifier for the node. |
| Elevation | Physical ground elevation of the injection point (length units). |
| Inflow | Base volumetric flow rate injected into the network (e.g., GPM, L/s, MGD). |
| Min / Max Inflow | Lower and upper bounds for live canvas interactive sliders and batch optimization ranges. |
| Min Pressure | Operational pressure threshold below which low-pressure alerts or cavitation flags trigger. |
| Pattern | Multiplier curve that varies the inflow rate over 24-hour diurnal or extended period cycles. |
| Enable Random Flow | Adds stochastic autocorrelation (Gaussian noise) to simulate real-time turbulent, un-metered flow variability. |
| Water Quality Dosage | Chemical dosage (mg/L) injected proportionally with the inflow stream. |
