What does hydrograph mean?
A hydrograph is a graph or plotted record showing how the level, flow, or discharge of water changes over time. It is commonly used in hydrology and civil engineering to represent conditions in a river, stream, lake, reservoir, or drainage system. A flood hydrograph, for example, may show the rise and fall of river discharge following heavy rainfall, while a streamflow hydrograph tracks changes through a particular measurement point. The term is also closely associated with hydrograph analysis, in which the timing, magnitude, and shape of the flow curve are examined. Although hydrographs can make complex water behavior easier to interpret, the word remains specialized and is not normally used in everyday conversation. Its importance lies in helping scientists and engineers compare events, assess flood risk, study watershed responses, and plan water-management infrastructure.
nounA graph or plotted record showing changes in the level, discharge, or flow of water in a river, stream, lake, or similar body of water over time.
- A graph or plotted record showing changes in the level, discharge, or flow of water in a river, stream, lake, or similar body of water over time.
"The flood hydrograph showed how quickly the river's discharge rose after the storm."
"The streamflow hydrograph records the daily volume of water passing through the gauging station."
"Engineers used the flood hydrograph to estimate how quickly runoff would reach the downstream reservoir."
Plural form used when referring to multiple graphs or plotted records of water-level or flow measurements.
"The researchers compared hydrographs from several rivers across the watershed."
A river's hydrograph is essentially its pulse chart, turning storms and water releases into a curve of changing flow over time.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does hydrograph come from?
Hydrograph combines hydro-, from Greek hýdōr meaning “water,” with -graph, ultimately from Greek graphein meaning “to write” or “to draw.” The formation reflects the original sense of a written or graphical representation of water-related measurements. Its close relatives, including hydrography, hydrometer, hydraulic, and hydrogen, likewise derive from the same ancient Greek element associated with water.
Related word forms
How hydrograph is actually used
This is chiefly a technical term used in hydrology, flood analysis, water-resource engineering, and related environmental sciences. In ordinary English, it should not be used for a graph of rainfall, which is normally called a hyetograph.
Easily confused with hydrograph
A hydrograph records changes in water level or flow, whereas a hyetograph records rainfall or other precipitation over time.