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Why doesn’t USGS measure gage height from the bottom of the stream?

Streams are like living things and are constantly changing. Sometimes streams erode, becoming deeper, while other times streams deposit sediment, becoming shallower. To understand how those changes can affect streamflow, we need to measure from a reference point that does not change over time, which is why gage datums are chosen to be below the base of a streambed. This means that the gage datum is a uniquely selected reference point for each gage site.


Gage Datum

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