The variability in discharge over the course of a year is commonly represented by a hydrograph with mean monthly discharge variations plotted over the annual time scale.
Making this assumption can greatly simplify the analysis involved in constructing a unit hydrograph, and it is necessary for the creation of a geomorphologic instantaneous unit hydrograph.
However, land management patterns that change the hydrograph and/or vegetation cover can act to increase or decrease channel migration rates.
In storm hydrology, an important consideration is the stream's discharge hydrograph, a record of how the discharge varies over time after a precipitation event.
More precisely, it produces the surface runoff hydrograph as a response to a rainfall hydrograph as input.
Another application involves the separation of groundwater flow and baseflow from streamflow in the field of catchment hydrology (i.e. a method of hydrograph separation).
The record of flow over time is called a hydrograph.
Although the pattern of the annual hydrograph is fairly predictable, its magnitude is not.
