SWMM Plot (publication spec)

Part of Agentic SWMM — install the project first for the executable toolchain (aiswmm CLI, SWMM solver, MCP servers).

Before calling plot — ask the user

When the user asks to plot, always ask these questions first before calling any plot tool:

1. Which entity? A specific node (junction / outfall) — by name — or a specific link (conduit) — by name?
   • List 3–5 high-peak-flow candidates from the run's RPT Link Flow Summary so the user can pick.
2. Which attribute? Node options: Total_inflow, Depth_above_invert, Volume_stored_ponded, Flow_lost_flooding. Link options: Flow_rate, Velocity, Depth.
3. Time window? Default is the full simulation (24h). Offer to limit to a focus day or HH:MM-HH:MM window if peaks occur in a short period.

Do NOT silently pick defaults. The user needs control — different plots answer different questions (peak inspection vs continuity vs flooding).

What this skill provides

• A plotting script that reads:
  • rainfall TIMESERIES from a SWMM .inp (one named series at a time);
  • flow series from a SWMM .out binary (via swmmtoolbox).
• Renders a paired rainfall + node-flow figure with a fixed publication style:
  • SI units (rain in mm per timestep or mm/h depending on rainKind);
  • rainfall on the top axis, inverted (depth grows downward);
  • flow on the bottom axis;
  • inward ticks, Arial, no auto title;
  • optional focusDay to crop to a single day; optional windowStart/windowEnd (HH:MM, only together with focusDay) for a sub-day window.

When to use this skill

Use after swmm-runner.swmm_run has produced both .inp and .out, and you want a single rainfall-vs-flow figure for one node (typically the model's outfall or the assigned upstream junction of a subcatchment of interest).

Do not use this skill for multi-node ensemble plots, exceedance curves, or sensitivity scans — those would belong to swmm-uncertainty / swmm-calibration (no plot tools there yet).

MCP tools

This skill backs three LLM-facing tools. plot_rain_runoff_si is routed through the MCP server; inspect_plot_options and map_run are direct Python handlers in the tool registry (agentic_swmm/agent/tool_handlers/swmm_plot.py and swmm_map.py).

1. inspect_plot_options — inspect a run directory (or an explicit .inp / .out path) and return the available rainfall series names, node IDs, and node output attributes. Call this before plot_run so you can pass real names instead of placeholders. Required args: run_dir (or inp_path + out_file). Read-only; auto-approved under the QUICK permission profile.

2. map_run — render the spatial network layout (subcatchments + conduits + outfalls) as a PNG. Reads the INP from the run directory automatically; pass inp to override. Required arg: run_dir. Optional: out_png, dpi, no_subcatchments, no_vertices.

3. plot_run (proxies to plot_rain_runoff_si on the MCP server) — create a paired rainfall + node-flow figure from a run directory. Required arg: run_dir. Supply either node or link (mutually exclusive) to select the lower panel. Optional: rain_ts, rain_kind, node_attr, out_png. Day-window cropping: pass focus_day (YYYY-MM-DD) to crop the axis to one calendar day; pass window_start and window_end (both HH:MM) to further narrow to a sub-day window — both require focus_day (the server rejects window_start/window_end without focus_day).

mcp/swmm-plot/server.js exposes one underlying tool:

4. plot_rain_runoff_si — low-level render call used by plot_run. Prefer plot_run (which accepts run_dir) over calling this directly.
   • Args:
     • inp (required): path to the SWMM .inp (the rainfall TIMESERIES is read from here).
     • out (required): path to the SWMM .out binary.
     • outPng (required): where to write the PNG.
     • rainTs (no usable default — the schema ships the self-documenting placeholder \x3Crainfall-series-name>, which fails at render time if not replaced; always supply the actual series name from the .inp [TIMESERIES] section via inspect_plot_options): name of the rainfall TIMESERIES inside the .inp.
     • rainKind (default "depth_mm_per_dt"): one of intensity_mm_per_hr, depth_mm_per_dt, cumulative_depth_mm.
     • dtMin (default 5): timestep of the rainfall series in minutes.
     • node (no usable default — the schema ships the self-documenting placeholder \x3Coutfall-or-junction>, which fails at render time if not replaced; always supply a real outfall or junction name via inspect_plot_options): node ID to plot from the .out.
     • nodeAttr (default "Total_inflow"): which swmmtoolbox attribute (e.g. Total_inflow, Lateral_inflow, Flow_lost_flooding).
     • dpi (default 300).
     • focusDay (optional, YYYY-MM-DD): crop axis to a single day plus padding.
     • windowStart / windowEnd (optional, HH:MM; only valid together with focusDay): sub-day time window within the focus day. Rejected with a clear error if used without focusDay.
     • padHours (default 2).

Recommended orchestration

inspect_plot_options  →  list available series + node names
swmm-runner.run_swmm_inp  →  model.inp + model.out
plot_run              →  outfall_flow.png  (or junction_flow.png)

Call inspect_plot_options first to get the real rainfall series name and outfall node name, then pass those to plot_run. If multiple nodes need to be plotted, call plot_run once per node with a different out_png path.

Conventions

• Strict publication style: do not write a title in the plot; titles belong to the surrounding document.
• SI units only.
• Rainfall axis is always inverted; depth grows downward so it doesn't overlap the flow series visually.

Known limitations

• Only one rainfall series is plotted at a time (rainTs is a single name); multi-gauge inputs need separate figures.