Real-time streamflow data available on USGS pages are PROVISIONAL data that have not been reviewed or edited. These data may be subject to significant change and are not citable until reviewed and approved by the U.S. Geological Survey.
The term "100-year flood" is used to describe the recurrence interval of floods. The 100-year recurrence interval means that a flood of that magnitude has a one percent chance of occurring in any given year.
Why is the discharge reported at a particular stage sometimes different in different years or at certain times in the same year?
A relationship is developed by USGS hydrographers between stage (usually expressed as feet) and discharge (usually expressed as cubic feet per second).
Why are there sometimes differences between river stages as reported by the National Weather Service and by USGS?
At some USGS stream-gage installations, NWS maintains a separate stage sensor that is serviced by NWS technicians.
Stream stage is an important concept when analyzing how much water is moving in a stream at any given moment.
Not directly. You cannot say that because a stream rises (doubles) from a 10-foot stage to a 20-foot stage that the amount of water flowing also doubles. Think of a cereal bowl with a rounded bottom. Pour one inch of milk in it.
Each reach is a continuous piece of surface water with similar hydrologic characteristics, such as a stretch of stream between two confluences or a lake.
Where does the USGS monitor stream water quality in real time? How can I see these sites on a map and get to the data?
Continuous real-time water quality information is at Water Quality Watch Real-Time Water Temperature.
The National Hydrography Dataset (NHD) is the culmination of cooperative efforts of the U.S. Environmental Protection Agency (EPA) and U.S. Geological Survey (USGS).
The idea is to combine spatial accuracy with detailed features, attributes, and values. Information such as flow paths, permanent reach IDs, and hydrologic ordering can now be used in modeling.