Does the forest have an impact on water storage and hydrology?
Rain falling on forested land is intercepted by the foliage of the canopy. Some of the rainwater that penetrates to the land surface flows into rivers, lakes and oceans. Some water penetrates the soil before resurfacing to join the surface flow, while some water becomes part of underground reserves of water or aquifers.
Forest cover plays a role in regulating hydrology (cycles of water flow). Since variables such as density of foliage, temperature, the humus (or decomposed vegetation) layer on the forest floor, permeability of soils, slope and geology all affect the flow of water, it is not possible to state categorically that forests increase or decrease water flow. It would be accurate to say, however, that forest cover does mitigate the effects of events such as tropical rainstorms or rapid snowmelt, reducing the likelihood of downstream flooding and extending the time during which water flows can recharge underground reserves.
The International Panel on Climate Change (IPCC) considers that water cycling is one of the most important environmental services provided by forests.
"Water cycling is another major environmental service of forests. One of the expected impacts that would result from a significant expansion of the extent of deforestation in Amazonia and other parts of Brazil would be a reduction in rainfall, especially during the dry season (Lean et al., 1996). Similar effects have been calculated for the effects of forests on rainfall in the Indian subcontinent (Harding, 1992), and tropical forest protection has been shown to generate drought mitigation and flood mitigation benefits in Indonesia (Pattanayak and Kramer, 2000) and Madagascar (Kramer et al., 1997)
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