Most of us perceive water flow as the speed or rate at which water appears to be moving, referred to as "current". Hydrologists and other environmental scientists use a more exact measure for rivers and streams, called "discharge" or "flow". It is defined as the volume of water moving past a particular point during a given time period. Discharge or flow (either term is acceptable) applies to rivers and streams and is reported as cubic feet per second (cfs) or cubic meters per second (cms).
The data presented on the Water Atlas represent how the current discharge of a river in cubic feet per second (cfs) compares to the historical average. Tables provide discharge values summarized for the entire river, and from individual stations along the river. The latter is more meaningful, since water flow/discharge can vary considerably in different parts of a stream, particularly in major river systems.
History: Measuring water flow began at the turn of the 19th century in response to the demand for water as large populations centers developed around streams. As in current times, these communities were using, and over-using, vast amounts of water for drinking, industry, transportation and waste disposal. Flow gages are also used in predicting flood events, protecting lives and property. The first federally-funded gaging station (flow monitoring station) was established on the Rio Grande in 1889, and the first flow gaging network (seven stations) was established in Kansas in 1895. Since this time, hundreds of gaging stations have been established by federal, state, county and municipal agencies, and by private organizations for purposes of water resource planning, flood control, irrigation, environmental restoration and navigation. In fact, stream gaging has become the backbone of virtually every water resource and water quality management program worldwide.