USGS Tracks Your Groundwater — The Data

Data source: ZipCheckup analysis of USGS National Water Information System (NWIS), daily values, parameter 72019 (depth to water level)

Beneath your house, your yard, and the street you drive on every day, there's water. Sometimes it's 10 feet down. Sometimes it's 900. The U.S. Geological Survey has been measuring exactly how deep it is — well by well, day by day — and all of that data is public.

ZipCheckup mapped the entire USGS groundwater monitoring network to ZIP codes. Here's what the data shows.

The Scale of Monitoring

The USGS tracks 506,398 wells across 3,050 ZIP codes through its National Water Information System. Each well reports depth-to-water-level measurements — how far below the surface the water table sits at any given time.

The national average well depth is 58.3 feet. The median is just 27 feet — meaning half of all monitored wells find water less than three stories underground.

But those averages mask enormous variation.

The Deepest Wells in America

Some parts of the country have to reach remarkably far to find water:

Idaho, Arizona, Nevada, and New Mexico dominate this list — arid states where groundwater sits deep beneath the desert floor. ZIP 16013 in Idaho has a monitoring well reaching nearly 1,000 feet below the surface.

For context, the Statue of Liberty from base to torch tip is 305 feet. Some of these wells go more than three times that deep just to reach water.

Where Water Is Rising Above Ground

On the opposite end, four ZIP codes show negative depth-to-water measurements — the water table has risen above the land surface:

• 13033 (GA) — Water at -21 feet (above ground), 4 wells
• 13039 (GA) — Water at -15 feet, 7 wells
• 13127 (GA) — Water at -1.5 feet, 25 wells
• 29143 (MO) — Water at -2.5 feet, 1 well

Negative readings indicate artesian conditions — underground pressure pushes water above the surface. In coastal Georgia, this is a known phenomenon tied to the Upper Floridan Aquifer, one of the most productive (and most stressed) aquifers in the southeastern United States.

These aren't just geological curiosities. Areas with rising water tables face increased flooding risk, foundation damage, and septic system failures.

The States With the Most Monitoring

Not all states have equal groundwater surveillance. Here are the most heavily monitored:

Washington state has only 39 monitored ZIP codes but leads in raw well count with 65,412 wells — heavily concentrated in the agricultural regions of eastern Washington where irrigation depends on groundwater.

California, despite its well-documented water struggles, monitors just 58 ZIP codes through USGS — but those wells average 123.4 feet deep, more than double the national average. New Mexico averages even deeper at 142 feet.

Why Groundwater Depth Matters for Your Home

Groundwater depth directly affects several things homeowners care about:

Shallow water tables (under 10 feet):

• Higher risk of basement flooding
• Septic systems may fail or require special engineering
• Foundation settling and soil instability
• Contaminants from surface can reach groundwater faster

Deep water tables (over 200 feet):

• Well drilling costs increase substantially
• Drought vulnerability — if the aquifer drops, your well goes dry
• May indicate declining water availability in the region

Changing water levels:

• Rising water tables can signal increased precipitation — or failing drainage infrastructure
• Falling water tables often indicate over-pumping, urbanization reducing recharge, or climate shifts

Whether your tap depends on those wells matters: across the 5,572 public utilities tracked in the CCR Rich Dataset, each system discloses its source-water type — groundwater, surface water, blended, or purchased — and groundwater-sourced systems are the ones most directly exposed to falling or rising water tables.

The Data Gap

One important limitation: USGS monitors 3,050 ZIP codes out of roughly 41,000 in the United States. That's about 7.4% coverage. If your ZIP code isn't monitored, it doesn't mean your groundwater is fine — it means nobody's measuring it.

The monitoring network is concentrated in areas with known groundwater issues or active research programs. Large swaths of the country, particularly in the Northeast and parts of the Midwest, have sparse coverage.

Check Your ZIP

ZipCheckup integrates USGS groundwater data alongside EPA water quality records, lead risk assessments, flood data, and dozens of other environmental factors. Enter your ZIP code to see what federal agencies know about the water beneath your feet — and flowing from your tap.

Check your ZIP code on ZipCheckup