The process by which precipitation is caught and held by vegetation canopy or other surface cover before reaching the ground. Intercepted water eventually evaporates back to the atmosphere.
Interception is the portion of precipitation that is captured by vegetation canopy, litter layers, or other surface covers and subsequently evaporated back to the atmosphere without reaching the soil surface. It includes canopy interception by leaves and branches, litter interception by dead organic material on the forest floor, and stem flow that channels water down tree trunks. In forested environments, interception losses can account for 10-40% of total precipitation, depending on forest type, canopy density, and storm characteristics. The process is most significant for light, short-duration rainfall events, where a larger proportion of total precipitation is retained by the canopy. Interception reduces the amount of water available for infiltration and runoff, thereby affecting the overall water balance of a catchment. Measurement typically involves comparing precipitation in the open (above canopy) with throughfall and stemflow beneath the canopy. Changes in interception due to deforestation, afforestation, or forest management can have measurable effects on streamflow and groundwater recharge at the catchment scale.