The region beneath and alongside the bed of a stream or river where the stream water and groundwater mix. Water can flow through the hyporheic zone as a consequence of upwelling of groundwater or seepage of stream water, giving rise to hyporheic (or interstitial) flow. This zone sees continual interchange of material between stream water and groundwater, which can impact on the quality of both, for example in terms of water chemistry and pollutant load. It is also important as a habitat, especially for microbial and invertebrate communities, and for fish spawning.
Subjects: Biological Sciences.