Decoding Official USGS Hydrology Telemetry
The U.S. Geological Survey (USGS) operates the world's most extensive, reliable network of freshwater streamgages and lake monitoring stations. However, visiting an official USGS monitoring page can be intimidating. The interface is packed with five-digit parameter codes, cryptic data qualifiers, and multiple vertical datums.
This guide walks you through every essential element on an official USGS station page so you can extract water levels, assess data quality, and evaluate flood trends with confidence.
---
1. Finding and Confirming the Station ID
Every USGS monitoring location is assigned a unique permanent 8- to 15-digit numeric identifier:
- Stations starting with `0` (e.g., `08154500` for Lake Travis nr Austin, TX) represent standard hydrologic basins numbered from east to west.
- Look for the official Site Name and Location Coordinates. Ensure the station measures the lake pool itself and not a tributary stream miles upstream.
---
2. Deciphering Essential USGS Parameter Codes
USGS stations record diverse environmental variables. When checking lake and reservoir conditions, look for these specific 5-digit parameter codes:
| Parameter Code | Description | Standard Unit |
| :--- | :--- | :--- |
| 62614 | Lake or reservoir water surface elevation | Feet above NGVD29 / NAVD88 |
| 62615 | Lake surface elevation | Meters |
| 00062 | Elevation of reservoir water surface | Feet (local or arbitrary datum) |
| 00065 | Gauge height (stream stage) | Feet |
| 00054 | Reservoir storage | Acre-feet |
| 00060 | Stream discharge / outflow | Cubic feet per second (cfs) |
If you are evaluating boat clearances, always look for 62614 (elevation) rather than 00065 (stage).
---
3. Understanding Data Qualifiers: Approved vs. Provisional
Beside every numeric reading in a USGS table, you will see a status qualifier letter:
- P (Provisional Data): The observation was transmitted automatically via satellite radio from an unmonitored electronic sensor. It has not yet been audited by a human hydrologist. While generally accurate, provisional data can occasionally reflect temporary sensor drift or debris fouling.
- A (Approved Data): The record has undergone rigorous quality-assurance review by USGS scientists and is considered official historical fact.
- e (Estimated Data): Assigned when sensor failure required hydrologists to interpolate values using neighboring stations or mathematical models.
At WaterLakeLevel, our server indicates whether each reading is approved or provisional right on the lake dashboard.
---
4. Checking the Vertical Datum
Look immediately beneath the parameter table for the Vertical Datum designation:
- NGVD 1929: National Geodetic Vertical Datum of 1929.
- NAVD 1988: North American Vertical Datum of 1988.
If you are comparing USGS elevation numbers against a property survey or boat ramp blueprint, ensure both figures use the same datum. A survey benchmark in NAVD88 will not match an NGVD29 lake reading without applying an adjustment offset!
---
5. How to Interpret the Hydrograph Trend Line
The graphical chart (hydrograph) on a USGS station page illustrates water changes over time:
- Steep Upward Slope: Indicates rapid watershed inflow from heavy storm runoff.
- Plateau / Flat Line: Reflects steady-state equilibrium where reservoir inflow matches downstream discharge.
- Gradual Downward Slope: Characteristic of seasonal dry periods driven by municipal water withdrawals and solar evaporation.