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Runoff is the flow of water across the earth, and is a major component in the hydrological cycle. Runoff that flows over land before reaching a watercourse is referred to as surface runoff or overland flow. Once in a watercourse, runoff is referred to as streamflow, channel runoff, or river runoff. Urban runoff is surface runoff created by ...
A runoff models or rainfall-runoff model describes how rainfall is converted into runoff in a drainage basin (catchment area or watershed). More precisely, it produces a surface runoff hydrograph in response to a rainfall event, represented by and input as a hyetograph. Rainfall-runoff models need to be calibrated before they can be used.
Runoff: The variety of ways by which water moves across the land. This includes both surface runoff and channel runoff. As it flows, the water may seep into the ground, evaporate into the air, become stored in lakes or reservoirs, or be extracted for agricultural or other human uses.
Surface runoff often occurs because impervious areas (such as roofs and pavement) do not allow water to soak into the ground. Furthermore, runoff can occur either through natural or human-made processes. [1] Surface runoff is a major component of the water cycle. It is the primary agent of soil erosion by water.
In hydrology, run-on refers to surface runoff from an external area that flows on to an area of interest. A portion of run-on can infiltrate once it reaches the area of interest. Run-on is common in arid and semi-arid areas with patchy vegetation cover and short but intense thunderstorms. In these environments, surface runoff is usually ...
Surface-water hydrology is the sub-field of hydrology concerned with above-earth water (surface water), in contrast to groundwater hydrology that deals with water below the surface of the Earth. Its applications include rainfall and runoff , the routes that surface water takes (for example through rivers or reservoirs ), and the occurrence of ...
The reason unimpaired runoff is important is because long-term hydrologic records are often used to develop relationships between precipitation, runoff, and water supply. By removing changes in the timing between precipitation and runoff due to human influences, the long-term relationships will be more useful.
This equation requires the system to be closed, and where it is not (for example when surface runoff contributes to a different basin), this must be taken into account. Extensive water balances are discussed in agricultural hydrology. A water balance can be used to help manage water supply and predict where there may be water shortages.