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Concept
Hyporheic zone
Summary
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 flow dynamics and behavior in this zone (termed hyporheic flow or underflow) is recognized to be important for surface water/groundwater interactions, as well as fish spawning, among other processes. As an innovative urban water management practice, the hyporheic zone can be designed by engineers and actively managed for improvements in both water quality and riparian habitat.
The assemblages of organisms that inhabits this zone are called .
The term hyporheic was originally coined by Traian Orghidan in 1959 by combining two Greek words: (below) and (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. Depending on the underlying geology and topography, the hyporheic zone can be only several centimeters deep, or extend up to tens of meters laterally or deep.
The conceptual framework of the hyporheic zone as both a mixing and storage zone are integral to the study of hydrology. The first key concept related to the hyporheic zone is that of residence time; water in the channel moves at a much faster rate compared to the hyporheic zone, so this flow of slower water effectively increases the water residence time within the stream channel. Water residence times influence nutrient and carbon processing rates. Longer residence times promote dissolved solute retention, which can be later released back into the channel, delaying or attenuating the signals produced by the stream channel.
The other key concept is that of hyporheic exchange, or the speed at which water enters or leaves the subsurface zone. Stream water enters the hyporheic zone temporarily, but eventually the stream water reenters the surface channel or contributes to groundwater storage.
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Fresh water
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include non-salty mineral-rich waters such as chalybeate springs. Fresh water may encompass frozen and meltwater in ice sheets, ice caps, glaciers, snowfields and icebergs, natural precipitations such as rainfall, snowfall, hail/sleet and graupel, and surface runoffs that form inland bodies of water such as wetlands, ponds, lakes, rivers, streams, as well as groundwater contained in aquifers, subterranean rivers and lakes.
Surface water
Surface water is water located on top of land, forming terrestrial (surrounding by land on all sides) waterbodies, and may also be referred to as blue water, opposed to the seawater and waterbodies like the ocean. The vast majority of surface water is produced by precipitation. As the climate warms in the spring, snowmelt runs off towards nearby streams and rivers contributing towards a large portion of human drinking water. Levels of surface water lessen as a result of evaporation as well as water moving into the ground becoming ground-water.
Water resources
Water resources are natural resources of water that are potentially useful for humans, for example as a source of drinking water supply or irrigation water. 97% of the water on Earth is salt water and only three percent is fresh water; slightly over two-thirds of this is frozen in glaciers and polar ice caps. The remaining unfrozen freshwater is found mainly as groundwater, with only a small fraction present above ground or in the air. Natural sources of fresh water include surface water, under river flow, groundwater and frozen water.