gaging

Gaging, also spelled gauging in some regions, refers to the measurement of a quantity, and in hydrology specifically to measuring water level and flow in rivers, streams, and other bodies of water. A gaging program collects data at fixed sites, known as gaging stations, to produce time series of stage (gage height) and discharge (Q) that are used to characterize hydrologic behavior.

Field methods include direct discharge measurements using current meters and velocity-area methods, as well as fixed structures like weirs or flumes that relate water depth to flow. Automated gages employ sensors such as pressure transducers, ultrasonic or radar level sensors, and Doppler devices to record stage continuously, with the discharge estimate derived from a stage-discharge rating curve or, in some cases, real-time hydrographs.

Data products from gaging networks support flood forecasting, dam safety assessments, water resources planning, environmental and ecological studies, and climate research. Gaging stations are maintained by national or regional agencies, and data are typically archived in central databases with varying levels of real-time accessibility.

Quality and interpretation depend on site selection, instrument calibration, and the validity of stage-discharge relationships. Gaging can be temporary for short-term studies or long-term for ongoing monitoring. Data gaps or sensor issues can affect records, requiring quality control and gap-filling techniques.

Prominent examples of gaging programs include the U.S. Geological Survey's stream gaging network and similar national programs worldwide that provide baseline hydrological data for research and public safety.