# Subsurface flow

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**Subsurface flow**, in [hydrology](/source/Hydrology), is the flow of water beneath Earth's surface as part of the [water cycle](/source/Water_cycle).

In the water cycle, when [precipitation](/source/Precipitation_(meteorology)) falls on the Earth's land, some of the water flows on the surface forming [streams](/source/Stream) and [rivers](/source/River). The remaining water, through [infiltration](/source/Infiltration_(hydrology)), penetrates the soil traveling underground, hydrating the [vadose zone](/source/Vadose_zone) soil, [recharging](/source/Groundwater_recharge) [aquifers](/source/Aquifer), with the excess flowing in subsurface runoff. In [hydrogeology](/source/Hydrogeology) it is measured by the [Groundwater flow equation](/source/Groundwater_flow_equation).

## Runoff

Water flows from areas where the [water table](/source/Water_table) is higher to areas where it is lower. This flow can be either [surface runoff](/source/Surface_runoff) in rivers and streams, or subsurface runoff infiltrating rocks and soil. The amount of runoff reaching surface and groundwater can vary significantly, depending on rainfall, soil moisture, [permeability](/source/Permeability_(earth_sciences)), groundwater storage, evaporation, upstream use, and whether or not the ground is frozen. The movement of subsurface water is determined largely by the water gradient, type of substrate, and any barriers to flow. The groundwater flow may be through either confined or phreatic aquifers, with smaller flow systems overlying or within. The residence time generally ranges from several decades to many centuries, implying the establishment of a complete chemical equilibrium with the aquifer. Mapping scales are between 1:250,000 and 1:2,000,000. (see, for example, Engelen et al. 1988).[1]

## Surface return

Subsurface water may return to the surface in [groundwater flow](/source/Groundwater_flow), such as from a [spring](/source/Spring_(hydrosphere)), [seep](/source/Seep_(hydrology)), or a [water well](/source/Water_well), or subsurface return to [streams](/source/Stream), [rivers](/source/River), and [oceans](/source/Ocean). Water returns to the land surface at a lower elevation than where infiltration occurred, under the force of gravity or gravity induced pressures. Groundwater tends to move slowly, and is replenished slowly, so it can remain in aquifers for thousands of years. Mainly, water flows through the ground which leads to the ocean where the cycle begins again.

## Subsurface flow

Flow within the soil body may take place under unsaturated conditions, but faster subsurface flow is associated with localized soil saturation.

## See also

- [Artesian aquifer](/source/Artesian_aquifer)
- [Ecohydrology](/source/Ecohydrology)
- [Groundwater](/source/Groundwater)
- [Groundwater energy balance](/source/Groundwater_energy_balance)
- [Groundwater flow](/source/Groundwater_flow)
- [Groundwater recharge](/source/Groundwater_recharge)
- [Vadose zone](/source/Vadose_zone)
- [Water cycle](/source/Water_cycle)

## References

1. Klijn, Frans & Witte, Jan-Philip M. (1999-02-01). ["Eco-hydrology: Groundwater flow and site factors in plant ecology"](https://doi.org/10.1007/s100400050180). *Hydrogeology Journal*. **7** (1): 65–77. [Bibcode:1999HydJ....7...65K](https://ui.adsabs.harvard.edu/abs/1999HydJ....7...65K). [doi:10.1007/s100400050180](https://doi.org/10.1007/s100400050180). [ISSN 1435-0157](https://www.worldcat.org/issn/1435-0157). [S2CID 140589530](https://api.semanticscholar.org/CorpusID:140589530)

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- [tutor.com](http://www.tutor.com)/
- Huggett, J. (2005) Fundamentals of Geomorphology, Routeledge, Oxon.

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Adapted from the Wikipedia article [Subsurface flow](https://en.wikipedia.org/wiki/Subsurface_flow) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Subsurface_flow?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.