User Guide | Illinois GW Monitoring Network

Groundwater is the invisible lifeblood of Illinois, supplying water to millions of people, industries, and acres of farmland. However, you can't manage what you don't measure!

The Illinois State Water Survey (ISWS) maintains a network of dedicated monitoring wells to observe the health of our aquifers in real-time. This dashboard allows scientists, drillers, and the public to visualize the pulse of our water resources instantly.

Located at the top of the dashboard, the Executive Summary provides a plain-English interpretation of the most recent data. It answers the question: "Is the water level normal for this time of year?"

It compares the latest reading against the well's entire history (often 20+ years of data) to assign a Condition ranking:

Much Above Normal: Water levels are higher than 90% of historical readings (Top 10%).
Above Normal: Higher than 75% of readings.
Normal: Between the 25th and 75th percentiles (The typical range).
Below Normal: Lower than 25% of readings.
Much Below Normal: Lower than 90% of readings (Bottom 10%).

Note: Conditions are calculated both for the "Overall" period of record and specifically for the current "Month," accounting for seasonal fluctuations.

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The centerpiece of the dashboard is the hydrograph, a chart which plots water levels over time. It is designed to be interactive, allowing you to interrogate the data rather than just look at a static image.

1. Two Ways to View Water: Elevation vs. Depth

Hydrogeologists and well owners often speak different languages. We've included a toggle button below the hydrograph to translate:

Groundwater Elevation (GWE): This is the default scientific view. It measures water height relative to Mean Sea Level (MSL). This is critical for determining which direction groundwater is flowing (always high to low).
Depth to Water (DTW): By clicking Convert to Depth to Water, the hydrograph flips. This measures how far down you would have to drop a tape measure from the surface to hit water. This is the practical number most well owners care about.

2. Navigating Time (The Time Slicer)

You don't need to squint at the entire history of the well at once.

Quick Ranges: Use the buttons at the top left of the hydrograph (1w, 1m, 1y) to instantly zoom into the most recent week, month, or year.
The Slider: At the very bottom of the hydrograph is a smaller "navigator" series. You can drag the handles on the left and right of this slider to focus on a specific drought event, season, or year of interest.

3. Telemetry vs. Field Measurements

You will notice two different data series on the hydrograph:

Telemetry (Blue Line): This data is collected by automated pressure transducers that wake up every hour, take a reading, and radio it back to ISWS servers in Champaign. They are relentless, but occasionally drift.
Field Measurements (Orange Dots): These represent when an ISWS hydrogeologist manually measures the depth to water in the monitoring well with an electric water level meter or a steel tape measure. These are our "ground truth" calibration points to ensure that the transducer readings are not drifting.

Tip: You can click on the names "Telemetry" or "Field Measurement" in the legend to toggle them on or off. This is useful if the hydrograph looks cluttered.

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Below the hydrograph, we have organized the context data into collapsible sections to keep the interface clean—especially on mobile devices.

Well Metadata: Click this header to reveal the well's "specifications", such as its depth, the aquifer it monitors, and its ISWS ID number.
Location Map: Click this header to verify where the well is located. The map is fully interactive; feel free to zoom out to see the regional context.

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For users who need deep context, this panel provides rigorous statistical analysis calculated on-the-fly using the entire historical record of the well.

The methodology used to calculate percentiles and medians strictly follows the standards established by the USGS National Ground-Water Monitoring Network.

1. Overall Statistics

This table displays the absolute lowest, highest, and median water levels ever recorded at this site. It also calculates the "Period of Record" in years.

2. Monthly Statistics

Groundwater levels are naturally seasonal. This table breaks down the data by month to show typical seasonal behavior. We highlight the Current Month row so you can easily compare today's reading against the historical average for this specific time of year.

Criteria: To ensure statistical validity, monthly statistics are only calculated for months where the well has at least 10 individual years with at least one measurement in the given month AND the well has been measured at least once in the preceding 406 days. If a month has insufficient history, those cells will remain empty.

Dynamic Updates: Both statistical tables automatically update based on your view settings. If you click Convert to Depth to Water, the statistics will recalculate to show depths instead of elevations.

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Science relies on transparency. If you are a researcher or consultant who needs the raw numbers, expand the Well Metadata section. At the bottom of the table, you will find a [ JSON ] link. This provides the raw data feed directly from our API.

Additionally, in the top right corner of the hydrograph, you will see a small menu icon (three horizontal lines). This allows you to print the hydrograph, download an image (PNG/JPEG), or enter "Full Screen" mode for your own reports or presentations.

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