Hyporheic zone

The hyporheic zone is the region of sediment and porous space beneath and alongside a stream bed, where there is mixing of shallow groundwater and surface water.

The term hyporheic was originally coined by Traian Orghidan[3] in 1959 by combining two Greek words: hypo (below) and rheos (flow).

The hyporheic zone is the area of rapid exchange, where water is moved into and out of the stream bed and carries dissolved gas and solutes, contaminants, microorganisms and particles with it.

[12] Researchers use tools such as wells and piezometers, conservative and reactive tracers,[13] and transport models that account for advection and dispersion of water in both the stream channel and the subsurface.

The hyporheic zone is an ecotone between the stream and subsurface: it is a dynamic area of mixing between surface water and groundwater at the sediment-water interface.

[15] As interface region between the main stream and the groundwater the hyporheic zone is subjected to physic-chemical gradients generating biochemical reactions able to regulate the behavior of the chemical compounds and the aquatic organisms within the exchange area.

[16] The hyporheic zone provides an important contribution to the attenuation of contaminants dissolved in the channel water[17] and to the cycle of energy, nutrients and organic compounds.