The runoff is a stream of water, which can come from rain , melting of snow or other sources, flowing over the surface of the earth when it has already exceeded the capacity of evaporation and infiltration that has land and is a main component of the water cycle . It can also be known as a runoff or spillway . Runoff has the ability to travel through the ground and expand freely, which is very important for humans because it allows, mainly, to collect water .

What is runoff?

It is an important phase of the hydrological cycle and it is the waters that can remain in constant movement on the surface of the earth due to the fall of the rain or the melting of snow, creating drainage systems .

  • What does it consist of
  • Surface runoff
  • Underground runoff
  • Hypodermic runoff
  • Effects edit
  • Prevention

What does it consist of

Runoff consists of a stream of water that originates from the different precipitations that occur and that circulates and spreads over the ground when the existing capacity for evaporation and infiltration of water into the ground has been exceeded and the ground it can no longer absorb it. It is for this reason that runoff goes through the soil and has the ability to expand with freedom .

This water that runs through the soil also feeds rivers, lakes, seas and oceans and also produces, as a negative effect, soil erosion .

Surface runoff

Surface runoff is the fastest type of runoff that exists in nature and is at the same time the one that mainly causes the process of soil erosion , as well as being an important part of the water cycle . It originates or derives from precipitation , from the melting of snow and glaciers . These runoffs are the ones that most frequently reach the waters of the oceans, rivers and seas and have the capacity to generate various damages to crops, trees, plants and vegetables.

It is important to mention that surface runoff can be affected many times by the different activities carried out by human beings , and for this reason it is that some of these waters that run freely through the soil also transport large amounts of garbage , chemicals and other wastes that negatively affect water and the environment .

Underground runoff

Groundwater runoff happens below ground after water has infiltrated through it. The water then circulates horizontally and then has the ability to flow outward again in the form of a spring . This type produces waters that can be used and that are available in periods of drought , but it must be remembered that they are not a renewable resource, so if these waters are extracted without control, there will be a depletion of the water resource. The speed at which the water moves in the underground runoff is very slow but its resistance timeis considerably high .

Hypodermic runoff

Hypodermic runoff is part of the precipitation that is able to infiltrate into the ground and that can circulate in the subsoil and this does so at a very shallow depth and at distances that are short, until it reaches the surface when it finds a flow channel through medium from which to rise, and then it becomes part of the surface runoff after the rain has passed, and does not get to feed the groundwater .

Effects edit

The main effects of runoff are as follows:


It is important to remember that soil is the surface layer of the earth’s surface that is made up of a series of organic and inorganic materials . One of the peculiarities of soils is that they are full of materials that are not consolidated , for example, clays, silts, sands, gravels, etc. And it is precisely this characteristic that makes soils so susceptible to erosion , mainly water erosion that occurs when runoff cannot be controlled.

Environmental impact

The main environmental problems that are associated with runoff are the impacts suffered by surface , groundwater and soil through the transport of water pollutants to these systems. These consequences produce risks to human health, disturbances of the ecosystem and the aesthetic impact on water resources .

Some of the pollutants that affect surface waters and that are derived from runoff are substances that come from oil , herbicides and fertilizers . In the case of surface waters, the impacts turn into water pollution , as streams and rivers have received chemicals . When surface water is a supply of drinking water , they are engaged causing risks for health .

Polluted surface waters run the risk of altering the metabolic processes of the aquatic species they harbor; producing the death of fish, or altering the balance of the populations present. It can also affect the mating of animals, spawning, viability of eggs and larvae, survival and productivity of water plants.


Some preventive measures against runoff are:

  • Public education to inform about ways to avoid contamination of rainwater.
  • Public participation in the implementation of local programs .
  • Detection and elimination of illegal downloads .
  • Runoff controls at construction sites .
  • Post-construction stormwater management controls .
  • Pollution prevention measures .

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