GUI

Hydra’s desktop application lets you load, run, and explore simulations without using the command line. It is the front end to every Hydra engine — today that means the water distribution engine; planned engines appear in the app but cannot yet be used.

Download and Install

Download the installer for your platform from the releases page.

macOS — “Hydra is damaged and can’t be opened”

Hydra GUI macOS releases are notarised. If Gatekeeper still shows this warning after dragging Hydra to Applications, run this once in Terminal:

xattr -cr /Applications/Hydra.app

Then open the app normally.

Basic Workflow

Hydra organises work into projects. Each project holds a network model and one or more scenarios — independent parameter sets you can run and compare.

1. Create a project — on the Projects screen, click New Project. The wizard asks for the engine first, then project details, then a review. Choosing the engine up front is deliberate: .inp belongs to both EPANET and SWMM, so the file extension cannot decide the modelling domain on your behalf. Engines marked as planned are shown but cannot be selected. With Water Distribution chosen, either import an existing EPANET .inp file or start from a blank network.
2. Configure and run — press ⌘R (macOS) or Ctrl+R (Windows/Linux), or click the Simulate button in the scenario strip at the bottom of the screen. Select which scenarios to run and confirm.
3. Explore results — after the simulation completes, the network map updates with colour-coded results. Click any node or link to inspect its time-series values (pressure, head, flow, velocity, water age, etc.). Use the timeline scrubber to step through reporting periods.

Press ⌘K (macOS) or Ctrl+K (Windows/Linux) at any time to open the command palette, which lists every action — running simulations, switching views, imports and exports — filtered as you type by substring match. Type # in the palette to find any node or link by ID and zoom to it.

Keyboard Shortcuts

Beyond ⌘R (simulate), ⌘K (command palette), and ⌘Z / ⇧⌘Z (undo/redo), the app has shortcuts for navigation and the canvas. Press ? at any time to open the in-app cheatsheet, or see the full Keyboard Shortcuts reference. Common ones (⌘ on macOS, Ctrl elsewhere):

On the canvas, single-key tools select elements and add or measure geometry (select, edit, add node, add link, measure), and annotations can be placed on the map.

Editing the Network

The Network tab provides editable tables for junctions, reservoirs, tanks, pipes, pumps, and valves, including each pipe’s initial status. Links are drawn as polylines, and their intermediate vertices are preserved and rendered on the canvas; dragging a node moves the link’s endpoint while the intermediate vertices stay fixed. Committed edits can be undone and redone with ⌘Z / ⇧⌘Z (Ctrl+Z / Ctrl+Shift+Z).

The Issues panel collects network validation findings (structural problems detected before a run) and warnings produced by the last simulation run, with links to the affected elements.

Dedicated editors are available for curves, patterns, and controls.

If a model’s coordinates use a projected coordinate system, the CRS picker on the canvas can scan the network’s coordinates and suggest matching coordinate reference systems so the network lines up with the basemap. You can also define and save custom CRS entries.

Scenarios and Comparison

Scenarios let you keep independent parameter sets side by side within one project. On the canvas, a comparison overlay can display the delta between the active scenario’s results and a baseline (the base model or another scenario).

The Analysis tab includes a system summary (key metric chips), result histograms, pipe criticality, pump energy, audit panels, and tank level charts.

Units

Choose between SI (metric) and US customary display units in Settings. This affects how values are shown and entered throughout the app; files and exports (INP, CSV, GeoJSON) always remain in the model’s native units. Settings also offers a light / dark / system theme.

Performance on Large Networks

Hydra GUI is tuned to stay responsive on larger models.

• Opening a project navigates immediately while network data finishes loading.
• Network Inspector node/link lists use virtualized rendering to avoid large DOM slowdowns.
• Basemap switching keeps network overlays attached so features remain visible while the style reloads.

Exporting and Output Files

Hydra saves simulation results inside the project folder on disk. To open the folder for a scenario, go to the Scenarios panel and click the Open in Finder icon next to the scenario name; it reveals the folder in your platform’s file manager (Finder, Explorer, or the Linux equivalent). The folder contains results.out — EPANET-compatible binary output, readable by post-processing tools.

Other formats are available from the command palette (⌘K / Ctrl+K):

• Export INP… — save the current network as an EPANET .inp file
• Export results as CSV… — save node and link result time series as CSV files (shown once results exist)
• Export results to GeoJSON — save nodes/links with attributes, including result values when available

For a plain-text .rpt report, run the exported .inp through the CLI.

Supported Networks

Any EPANET .inp file works directly — any 2.x release, no conversion needed. See INP Format Support for the full coverage list.

Troubleshooting

See the Troubleshooting page for common issues including the macOS Gatekeeper error and Windows Defender prompts.