Visualization

Last updated on 2026-06-16 | Edit this page

Overview

Questions

  • How do I visualize my NextGen runs?

Objectives

  • Explain how the Data Visualizer complements NGIAB.
  • Use the Data Visualizer to visualize results of a NextGen run in NGIAB.

Data Visualizer

The Data Visualizer component developed using the Tethys Platform (Swain et al., 2015) complements NGIAB by providing an environment for geospatial and time series visualization of catchments and nexus points (locations where objects in the hydrofabric like streams or water bodies connect). Through a web-based architecture, researchers can explore hydrological data in a spatiotemporal context (CIROH, 2025). In addition to standard map-based displays, this component also supports the visualization of the TEEHR output, including tabular metrics and interactive time series plots.

A screenshot of the NGIAB and DataStream Visualizer web interface. The map displays a the Provo River basin network near Woodland, UT. The gray shaded area represents the basin, dark gray lines represent catchment boundaries, black lines represent major streams, and blue circles with numbers in the middle represent the number of nexus points near that circle.
Figure 1: A map showing the geospatial visualization using the Data Visualizer within the Tethys framework for an entire study area (Provo River near Woodland, UT).

Using the Data Visualizer with NGIAB

ViewOnTethys Script

Like TEEHR, the Data Visualizer can be activated upon execution of the main NGIAB guide script, guide.sh. A separate viewOnTethys.sh script is also available in the NGIAB-CloudInfra repository.

Once a run is complete, users can launch the Data Visualizer through their web browser when prompted by the guide script. Although TEEHR’s outputs can be displayed within the Data Visualizer, this tool is primarily designed to provide a broad overview of model results. Users seeking TEEHR’s more advanced analysis features can still access them outside the Data Visualizer.

One of the advantages of the viewOnTethys.sh script is that it allows the user to keep multiple outputs for the same hydrofabric. It prompts the user if they want to use the same output directory by renaming it and adding it to the collection of outputs or if they want to overwrite it.

BASH 


  ⚠ ~/ngiab_visualizer is not empty.
  → Keep (K) or Fresh start (F)? [K/F]: k
ℹ Reclaiming ownership of ~/ngiab_visualizer  (sudo may prompt)…
  ⚠ Directory exists: ~/ngiab_visualizer/gage-10154200
  → Overwrite (O) or Duplicate (D)? [O/D]: o
  ✓ Overwritten ➜ ~/ngiab_visualizer/gage-10154200
Checking for ~/ngiab_visualizer/ngiab_visualizer.json...

You should be able to see multiple outputs through the UI:

A screenshot of the NGIAB and DataStream Visualizer web interface. The map displays the ability of the visualizer to use multiple outputs
Figure 2: NGIAB Visualizer dropdown for multiple outputs

Visualizer Directory Organization

The Visualizer organizes data using a directory named ngiab_visualizer. This directory stores all the outputs generated by the user and includes a file called ngiab_visualizer.json. This file contains metadata that allows the Visualizer to locate and manage the outputs from different runs executed via the ./guide.sh script. The metadata, specific to the Visualizer, is structured as a simple JSON file. It lists the outputs with details such as a label, the data path, and a unique identifier. The ./ViewOnTethys.sh script handles the creation and management of this metadata.

JSON 

{
  "model_runs": [
    {
      "label": "gage-10154200",
      "path": "/var/lib/tethys_persist/ngiab_preprocess_output/gage-10154200",
      "date": "2025-05-23:13:51:51",
      "id": "61026834-4235-4d39-8a8e-f076a8854148",
      "subset": "",
      "tags": []
    },
    {
      "label": "gage-20454200",
      "path": "/var/lib/tethys_persist/ngiab_visualizer/gage-20454200",
      "date": "2025-05-23:17:00:34",
      "id": "68f6cf78-188c-4e86-b797-6c40ea36e0e6",
      "subset": "",
      "tags": []
    },
    {
      "label": "gage-35054600",
      "path": "/var/lib/tethys_persist/ngiab_visualizer/gage-35054600",
      "date": "2025-05-23:17:01:10",
      "id": "6d0cb736-2dac-4ea0-a3a3-ad26cd45ef36",
      "subset": "",
      "tags": []
    }
  ]
}

The path /var/lib/tethys_persist/ belongs to the $HOME env variable of the container running the visualizer. When the user runs the ./ViewOnTethys.sh, it mounts the directory from the host at ~/ngiab_visualizer to /var/lib/tethys_persist/ngiab_visualizer.

However, if the user wants more control, the user can copy their data directory to ~/ngiab_visualizer on the host (not the container) while the container is stopped:

BASH 

sudo chown -R $USER: ~/ngiab_visualizer
cp -R your/data/path ~/ngiab_visualizer

Alternatively, the user can open the ~/ngiab_visualizer/ngiab_visualizer.json on the host (not the container), and add the specific run to the visualizer:

JSON 

....
    {
      "label": "gage-35054600",
      "path": "/var/lib/tethys_persist/ngiab_visualizer<MY_SPECIFIC_OUTPUT_DIRECTORY_NAME>",
      "date": "2025-05-23:17:01:10",
      "id": "6d0cb736-2dac-4ea0-a3a3-ad26cd45ef36",
      "subset": "",
      "tags": []
    }

The user can then run ./ViewOnTethys.sh script to spin up the container again, or if the user wants more control, they can export the env variables and run the container.

BASH 

export CONFIG_FILE="$HOME/.host_data_path.conf"          \
       TETHYS_CONTAINER_NAME="tethys-ngen-portal"        \
       TETHYS_REPO="awiciroh/tethys-ngiab"               \
       TETHYS_TAG="latest"                               \
       NGINX_PORT=80                                     \
       MODELS_RUNS_DIRECTORY="$HOME/ngiab_visualizer"    \
       DATASTREAM_DIRECTORY="$HOME/.datastream_ngiab"    \
       VISUALIZER_CONF="$MODELS_RUNS_DIRECTORY/ngiab_visualizer.json" \
       TETHYS_PERSIST_PATH="/var/lib/tethys_persist"     \
       SKIP_DB_SETUP=false                               \
       CSRF_TRUSTED_ORIGINS="[\"http://localhost:${NGINX_PORT}\",\"http://127.0.0.1:${NGINX_PORT}\"]"

BASH 

docker run --rm -d \
  -v "$MODELS_RUNS_DIRECTORY:$TETHYS_PERSIST_PATH/ngiab_visualizer" \
  -v "$DATASTREAM_DIRECTORY:$TETHYS_PERSIST_PATH/.datastream_ngiab" \
  -p "$NGINX_PORT:$NGINX_PORT" \
  --name "$TETHYS_CONTAINER_NAME" \
  -e MEDIA_ROOT="$TETHYS_PERSIST_PATH/media" \
  -e MEDIA_URL="/media/" \
  -e SKIP_DB_SETUP="$SKIP_DB_SETUP" \
  -e DATASTREAM_CONF="$TETHYS_PERSIST_PATH/.datastream_ngiab" \
  -e VISUALIZER_CONF="$TETHYS_PERSIST_PATH/ngiab_visualizer/ngiab_visualizer.json" \
  -e NGINX_PORT="$NGINX_PORT" \
  -e CSRF_TRUSTED_ORIGINS="$CSRF_TRUSTED_ORIGINS" \
  "${TETHYS_REPO}:${TETHYS_TAG}"

You should see something like this using docker ps

BASH 

docker ps

CONTAINER ID   IMAGE                          COMMAND                  CREATED          STATUS                             PORTS                                 NAMES
b1818a03de9b   awiciroh/tethys-ngiab:latest   "/usr/local/bin/_ent…"   25 seconds ago   Up 24 seconds (health: starting)   0.0.0.0:80->80/tcp, [::]:80->80/tcp   tethys-ngen-portal

Once it’s healthy, you can access the visualizer at:

http://localhost:${NGINX_PORT}

The ViewOnTethys.sh script automates updating ngiab_visualizer.json and copying your model output into ~/ngiab_visualizer.

Key Points

Key points

  • ViewOnTethys.sh automates adding model outputs to ngiab_visualizer.json and syncing data to ~/ngiab_visualizer.
  • To customize your setup, set environment variables and run the awiciroh/tethys-ngiab Docker image manually.

NGIAB Visualizer UI

The following figures demonstrate several ways the Data Visualizer can be used to visualize model outputs, including geospatial visualization for nexus points, catchment-based visualization, and TEEHR time series representation (hydrographs).

Nexus points can be visualized when the user selects the output that wants to visualize. Time series can be retrieved by clicking on any of the Nexus points, or by changing the select dropdown assigned to the Nexus.

A screenshot of the NGIAB and DataStream Visualizer web interface. The map displays the ability of the visualizer to retrieve time series from Nexus points
Figure 3: NGIAB Visualizer time series visualization from Nexus points

Troute variables time series can also be displayed using the Troute select dropdown.

A screenshot of the NGIAB and DataStream Visualizer web interface. The map displays the ability of the visualizer to retrieve time series from Troute variables
Figure 4: NGIAB Visualizer time series visualization from Troute variables

Catchments time series can be retrieved by clicking on any of the Catchments polygons, or by changing the select dropdown assigned to the Catchments.

A screenshot of the NGIAB and DataStream Visualizer web interface. The map displays the ability of the visualizer to retrieve time series from Catchments variables
Figure 5: NGIAB Visualizer time series visualization for Catchments

The TEEHR evaluation can be visualized when the user hits a point that contains TEEHR evaluation output. The user can also look at a Nexus point on the dropdown assigned and enter the id of the Nexus points that contains TEEHR evaluation output.

A screenshot of the NGIAB and DataStream Visualizer web interface. The left panel contains a "Time Series Menu" where the user can select a Nexus ID, variable (e.g., flow), and TEEHR data source. A map in the center displays a stream reach with a highlighted section representing the drainage basin and a blue point, indicating the selected nexus location. Below the map, a time series plot compares USGS (blue line) and Ngen (orange line) streamflow data from 2017 to 2023.
Figure 6: A map showing the geospatial visualization using the Data Visualizer within the Tethys framework for a selected outlet nexus point as well as displaying a time series plot between observed (labeled “USGS”; blue line) and simulated (labeled “ngen”; orange line)

Similarly, a TEEHR evaluation metric can be visualized by going to the metrics tab

A screenshot of the NGIAB and DataStream Visualizer web interface. The map displays the ability of the visualizer to retrieve the TEEHR metrics on a table."Teehr Metrics" presents performance metrics (e.g., Kling-Gupta Efficiency, Nash-Sutcliffe Efficiency, and Relative Bias) for the selected model versus reference data.
Figure 7: NGIAB Visualizer performance metrics (KGE, NSE, and relative bias). The Visualizer can also show the performance of the NWM 3.0 compared to the observed time series.
Callout

Using Data Visualizer with SSH

To use the Data Visualizer through a Secure Shell (SSH) connection, you will have to set up port forwarding when connecting to the remote machine. Port forwarding will allow you to access a remotely hosted browser session on your local machine. See the instructions under “Using NGIAB through an SSH connection” in the Advanced Topics episode in this training module.

Your Turn

Use the ViewOnTethys.sh script to launch the Data Visualizer in Docker, then open http://localhost:${NGINX_PORT} in your browser. Explore at least three different visualization modes—such as Nexus time series, catchment hydrographs, and TEEHR performance metrics. Next, edit ~/ngiab_visualizer/ngiab_visualizer.json to add a new model run (define its label and path), restart the visualizer, and confirm it appears in the dropdown menu.

Key Points
  • The Data Visualizer (built on the Tethys Platform) provides interactive geospatial maps and time series plots for NextGen model outputs in NGIAB.
  • It integrates seamlessly with NGIAB via guide.sh or ViewOnTethys.sh.
  • Model outputs reside under ~/ngiab_visualizer, with metadata stored in ngiab_visualizer.json.
  • You can visualize Nexus points, catchment summaries, Troute variables, and TEEHR hydrographs and performance metrics.