How the USGS Measures Water

Learn how river "stage" relates to streamflow and discharge, and how the USGS calculates them.

The USGS collects data about the country's water resources including the quantity and quality of water in our streams, rivers, groundwater, and more.

"Hydro" comes from the Greek word for... water. Hydrology is the study of water and hydrologists are scientists who study water. Read on to learn more.

If you have to spend time in other people's shoes before judging them, you'd have to do a lot more than walk a mile to understand a USGS water scientist. For example, if you were Hydrologic Technician, or "Hydrotech," John Jastram, you would be perched 40 feet above a river as you made water-quality measurements from a swaying cable car. And if you were Hydrotech Karl Dydak, you would actually be...

There are many pieces of equipment, both mechanical and electronic, that are installed at stream-monitoring sites all around the world to measure, record, and transmit both water-quantity and water-quality information. The U.S. Geological Survey (USGS) monitors "real-time" streamflow and water-quality conditions for thousands of streams nationwide.

The maximum height rivers reach during storms and floods is an important "data point" to document. In places where there are not dedicated monitoring equipment, the U.S. Geological Survey (USGS) often uses "crest stage gages" to record a one-time measurement of the flood peak.

At places where the U.S. Geological Survey (USGS) does not have real-time monitoring equipment, we use high-water marks to measure the maximum height (stream stage) of a flood or high-water event.