09/02/2026
Ever wonder how USGS keeps streamflow data accurate? 💧
📏One of the unsung heroes of our streamgages is the staff plate—the vertical ruler that shows the water level (or “gage height”). To make sure those readings stay trustworthy, we routinely run levels at our gages, which is a process using a levels rod to check elevation at designated object points around the site.
Object points comprise each point that is surveyed during a levels run: reference marks (specific, permanent locations we’ve identified as references for maintaining gage datum), reference points, gages, water surface, and other points. They can be t‑posts, rebar, bolts on larger structures, or even large, stable rocks. Some of these points are installed in the most secure spots we can find and help us confirm that the staff plate hasn’t shifted over time. Others act as backup reference points—helping us obtain a reliable gage height when the staff plate is damaged or inaccessible after storms or floods.
By validating both staff plates and object points, we ensure our gage heights—and ultimately our published streamflow data—are as accurate as possible. It’s careful work that keeps the nation’s water information dependable.
📷1: Hydrologic technician, Liam Mccann, verifies the staff plate is level.
📷2: A closer look at the verification process Liam is doing.
📷3: Liam uses a levels rod to check elevation at designated object points around the site.
Credit: Cory Rogaczewski
