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 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.[1]

The assemblage of organisms which inhabits this zone are called hyporheos.

The term hyporheic was originally coined by Traian Orghidan[2] in 1959 by combining two Greek words: hypo (below) and rheos (flow).

Hyporheic Zone and Hydrology

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 [3]. Depending on the underlying geology and topography, the hyporheic zone can be only several centimeters deep, or extend up to 10s 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 [4].

The other key concept is that of hyporheic exchange [5][6], 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. The rate of hyporheic exchange is influenced by streambed structure, with shorter water flow paths created by streambed roughness [7][8]. Longer flowpaths are induced by geomorphic features, such as stream meander patterns, pool-riffle sequences, large woody debris dams, and other features.

The hyporheic zone and its interactions influence the volume of stream water is moved downstream. Gaining reaches indicate that groundwater is discharged into the stream as water moves downstream, so that the volume of water in the main channel increases from upstream to downstream. Conversely, when water infiltrates into the groundwater zone resulting in a net loss of surface water, the stream reach is considered to be "losing" water.

Studying the Hyporheic Zone

A stream or river ecosystem is more than just the flowing water that can be seen on the surface: rivers are connected to the adjacent riparian areas [9]. Therefore, streams and rivers include the dynamic hyporheic zone that lies below and lateral to the main channel. Because the hyporheic zone lies underneath the surface water, it can be difficult to identify, quantify, and observe. However, the hyporheic zone is a zone of biological and physical activity, and therefore has functional significance for stream and river ecosystems [10]. Research scientists use tools such as wells and piezometers, conservative and reactive tracers [11], and transport models that account for advection and dispersion of water in both the stream channel and the subsurface [12]. These tools can be used independently to study water movement through the hyporheic zone and to the stream channel, but are often complimentary for a more accurate picture of water dynamics in the channel as a whole.

Biogeochemical Significance

The hyporheic zone is an ecotone between the stream and subsurface: it is dynamic area of mixing between surface water and groundwater at the sediment-water interface. From a biogeochemical perspective, groundwater is often low in dissolved oxygen but carries dissolved nutrients. Conversely, stream water from the main channel contains higher dissolved oxygen and lower nutrients. This creates a biogeochemical gradient, which can exist at varying depths depending on the extent of the hyporheic zone. Often, the hyporheic zone is dominated by heterotrophic microorganisms that process the dissolved nutrients exchanged at this interface.


  1. ^ Lawrence, J.E.; M. Skold; F.A. Hussain; D. Silverman; V.H. Resh; D.L. Sedlak; R.G. Luthy; J.E. McCray (14 August 2013). "Hyporheic Zone in Urban Streams: A Review and Opportunities for Enhancing Water Quality and Improving Aquatic Habitat by Active Management". Environmental Engineering Science. 47: 480–501. doi:10.1089/ees.2012.0235.
  2. ^ Orghidan, T. (1959). "Ein neuer Lebensraum des unterirdischen Wassers: Der hyporheische Biotop". Archiv für Hydrobiologie. 55: 392–414.
  3. ^ Bencala, Kenneth E. (2000). "Hyporheic zone hydrological processes". Hydrological Processes. 14 (15): 2797–2798. doi:10.1002/1099-1085(20001030)14:153.0.CO;2-6. ISSN 1099-1085.
  4. ^ Grimm, Nancy B.; Fisher, Stuart G. (1984-04-01). "Exchange between interstitial and surface water: Implications for stream metabolism and nutrient cycling". Hydrobiologia. 111 (3): 219–228. doi:10.1007/BF00007202. ISSN 1573-5117.
  5. ^ Findlay, Stuart (1995). "Importance of surface-subsurface exchange in stream ecosystems: The hyporheic zone". Limnology and Oceanography. 40 (1): 159–164. doi:10.4319/lo.1995.40.1.0159. ISSN 1939-5590.
  6. ^ Bencala, Kenneth E. (2006), "Hyporheic Exchange Flows", Encyclopedia of Hydrological Sciences, American Cancer Society, doi:10.1002/0470848944.hsa126, ISBN 9780470848944, retrieved 2019-03-15
  7. ^ Kasahara, Tamao; Wondzell, Steven M. (2003). "Geomorphic controls on hyporheic exchange flow in mountain streams". Water Resources Research. 39 (1): SBH 3–1–SBH 3-14. doi:10.1029/2002WR001386. ISSN 1944-7973.
  8. ^ Harvey, Judson W.; Bencala, Kenneth E. (1993). "The Effect of streambed topography on surface-subsurface water exchange in mountain catchments". Water Resources Research. 29 (1): 89–98. doi:10.1029/92WR01960. ISSN 1944-7973.
  9. ^ "An ecosystem perspective of alluvial rivers: connectivity and the hyporheic corridor | Scinapse | Academic search engine for paper". Scinapse. Retrieved 2019-03-15.
  10. ^ Boulton, Andrew J.; Findlay, Stuart; Marmonier, Pierre; Stanley, Emily H.; Valett, H. Maurice (1998-11-01). "The functional significance of the hyporheic zone in streams and rivers". Annual Review of Ecology and Systematics. 29 (1): 59–81. doi:10.1146/annurev.ecolsys.29.1.59. ISSN 0066-4162.
  11. ^ Mulholland, Patrick J.; Tank, Jennifer L.; Sanzone, Diane M.; Wollheim, Wilfred M.; Peterson, Bruce J.; Webster, Jackson R.; Meyer, Judy L. (2000). "Nitrogen Cycling in a Forest Stream Determined by a 15n Tracer Addition". Ecological Monographs. 70 (3): 471–493. doi:10.1890/0012-9615(2000)070[0471:NCIAFS]2.0.CO;2. ISSN 1557-7015.
  12. ^ Bencala, Kenneth E.; Walters, Roy A. (1983). "Simulation of solute transport in a mountain pool-and-riffle stream: A transient storage model". Water Resources Research. 19 (3): 718–724. doi:10.1029/WR019i003p00718. ISSN 1944-7973.

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Aquatic ecosystem

An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.


Benthos is the community of organisms that live on, in, or near the seabed, river, lake, or stream bottom, also known as the benthic zone. This community lives in or near marine or freshwater sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths.

Many organisms adapted to deep-water pressure cannot survive in the upperparts of the water column. The pressure difference can be very significant (approximately one atmosphere for each 10 metres of water depth).Because light is absorbed before it can reach deep ocean-water, the energy source for deep benthic ecosystems is often organic matter from higher up in the water column that drifts down to the depths. This dead and decaying matter sustains the benthic food chain; most organisms in the benthic zone are scavengers or detritivores.

The term benthos, coined by Haeckel in 1891, comes from the Greek noun βένθος "depth of the sea". Benthos is used in freshwater biology to refer to organisms at the bottom of freshwater bodies of water, such as lakes, rivers, and streams. There is also a redundant synonym, benthon.

Brown's Creek (St. Croix River)

Brown's Creek is a 9.7-mile-long (15.6 km) stream which originates about 5.5 miles northwest of the city of Stillwater and flows south for about half its length then east to its confluence with the St. Croix River just north of Stillwater in Washington County, Minnesota, United States. It is one of few creeks in the Minneapolis – Saint Paul "Twin Cities" metropolitan area that supports a fishable trout population.


The Capniidae, the small winter stoneflies, are a family of insects in the stonefly order (Plecoptera). It constitutes one of the largest stonefly families, containing some 300 species distributed throughout the holarctic. Their closest relatives are the rolled-winged stoneflies (Leuctridae).Many species are endemic to small ranges, perhaps due to the family's tendency to evolve tolerance for cold (isolating populations in mountain valleys) and winglessness (inhibiting dispersal). Indeed, some wingless Capniidae – e.g. the Lake Tahoe benthic stonefly ("Capnia" lacustra, Capnia is not monophyletic and this species is suspected to belong elsewhere) or Baikaloperla spp. – spend their entire lifecycles under water and do not disperse from their native lakes at all.

Drought refuge

A drought refuge is a site that provides permanent fresh water or moist conditions for plants and animals, acting as a refuge habitat when surrounding areas are affected by drought and allowing ecosystems and core species populations to survive until the drought breaks. Drought refuges are important for conserving ecosystems in places where the effects of climatic variability are exacerbated by human activities.

Emily Stanley

Emily Stanley is an American professor of limnology at the University of Wisconsin–Madison. She was named a 2018 Ecological Society of America Fellow and her research focuses on the ecology of freshwater ecosystems.

Floodplain restoration

Floodplain restoration is the process of fully or partially restoring a river's floodplain to its original conditions before having been affected by the construction of levees (dikes) and the draining of wetlands and marshes.

The objectives of restoring floodplains include the reduction of the incidence of floods, the provision of habitats for aquatic species, the improvement of water quality and the increased recharge of groundwater.

Fresh water

Fresh water (or freshwater) is any naturally occurring water except seawater and brackish water. Fresh water includes water in ice sheets, ice caps, glaciers, icebergs, bogs, ponds, lakes, rivers, streams, and even underground water called groundwater. Fresh water is generally characterized by having low concentrations of dissolved salts and other total dissolved solids. Though the term specifically excludes seawater and brackish water, it does include mineral-rich waters such as chalybeate springs.

Fresh water is not the same as potable water (or drinking water). Much of the earth's fresh water (on the surface and groundwater) is unsuitable for drinking without some treatment. Fresh water can easily become polluted by human activities or due to naturally occurring processes, such as erosion.

Water is critical to the survival of all living organisms. Some organisms can thrive on salt water, but the great majority of higher plants and most mammals need fresh water to live.

Freshwater environmental quality parameters

Freshwater environmental quality parameters are the natural and man-made chemical, biological and microbiological characteristics of rivers, lakes and ground-waters, the ways they are measured and the ways that they change. The values or concentrations attributed to such parameters can be used to describe the pollution status of an environment, its biotic status or to predict the likelihood or otherwise of a particular organisms being present. Monitoring of environmental quality parameters is a key activity in managing the environment, restoring polluted environments and anticipating the effects of man-made changes on the environment.

Freshwater environmental quality parameters are those chemical, physical or biological parameters that can be used to characterise a freshwater body. Because almost all water bodies are dynamic in their composition, the relevant quality parameters are typically expressed as a range of expected concentrations.

Limnodrilus hoffmeisteri

Limnodrilus hoffmeisteri, also known as red worm, is one of the most widespread and abundant oligochaetes in the world.


Limnology ( lim-NOL-ə-jee; from Greek λίμνη, limne, "lake" and λόγος, logos, "knowledge"), is the study of inland aquatic ecosystems.

The study of limnology includes aspects of the biological, chemical, physical, and geological characteristics and functions of inland waters (running and standing waters, fresh and saline, natural or man-made). This includes the study of lakes, reservoirs, ponds, rivers, springs, streams, wetlands, and groundwater. A more recent sub-discipline of limnology, termed landscape limnology, studies, manages, and seeks to conserve these ecosystems using a landscape perspective, by explicitly examining connections between an aquatic ecosystem and its watershed. Recently, the need to understand global inland waters as part of the Earth System created a sub-discipline called global limnology. This approach considers processes in inland waters on a global scale, like the role of inland aquatic ecosystems in global biogeochemical cycles.Limnology is closely related to aquatic ecology and hydrobiology, which study aquatic organisms and their interactions with the abiotic (non-living) environment. While limnology has substantial overlap with freshwater-focused disciplines (e.g., freshwater biology), it also includes the study of inland salt lakes.

List of watershed topics

This list embraces topographical watersheds and drainage basins and other topics focused on them.

Particle (ecology)

In marine and freshwater ecology, a particle is a small object. Particles can remain in suspension in the ocean or freshwater. However, they eventually settle (rate determined by Stokes' law) and accumulate as sediment. Some can enter the atmosphere through wave action where they can act as cloud condensation nuclei (CCN). Many organisms filter particles out of the water with unique filtration mechanisms (filter feeders). Particles are often associated with high loads of toxins which attach to the surface. As these toxins are passed up the food chain they accumulate in fatty tissue and become increasingly concentrated in predators (see bioaccumulation). Very little is known about the dynamics of particles, especially when they are re-suspended by dredging. They can remain floating in the water and drift over long distances. The decomposition of some particles by bacteria consumes a lot of oxygen and can cause the water to become hypoxic.

Photic zone

The photic zone, euphotic zone (Greek for "well lit": εὖ "well" + φῶς "light"), or sunlight (or sunlit) zone is the uppermost layer of water in a lake or ocean that is exposed to intense sunlight. It corresponds roughly to the layer above the compensation point, i.e. depth where the rate of carbon dioxide uptake, or equivalently, the rate of photosynthetic oxygen production, is equal to the rate of carbon dioxide production, equivalent to the rate of respiratory oxygen consumption, i.e. the depth where net carbon dioxide assimilation is zero.

It extends from the surface down to a depth where light intensity falls to one percent of that at the surface, called the euphotic depth. Accordingly, its thickness depends on the extent of light attenuation in the water column. Typical euphotic depths vary from only a few centimetres in highly turbid eutrophic lakes, to around 200 meters in the open ocean. It also varies with seasonal changes in turbidity.

Since the photic zone is where almost all of the photosynthesis occurs, the depth of the photic zone is generally proportional to the level of primary production that occurs in that area of the ocean. About 90% of all marine life lives in the photic zone. A small amount of primary production is generated deep in the abyssal zone around the hydrothermal vents which exist along some mid-oceanic ridges.

The zone which extends from the base of the euphotic zone to about 200 metres is sometimes called the disphotic zone. While there is some light, it is insufficient for photosynthesis, or at least insufficient for photosynthesis at a rate greater than respiration. The euphotic zone together with the disphotic zone coincides with the epipelagic zone. The bottommost zone, below the euphotic zone, is called the aphotic zone. Most deep ocean waters belong to this zone.

The transparency of the water, which determines the depth of the photic zone, is measured simply with a Secchi disk. It may also be measured with a photometer lowered into the water.

Ramsar site

A Ramsar site is a wetland site designated to be of international importance under the Ramsar Convention.The Convention on Wetlands, known as the Ramsar Convention, is an intergovernmental environmental treaty established in 1971 by UNESCO, which came into force in 1975. It provides for national action and international cooperation regarding the conservation of wetlands, and wise sustainable use of their resources.Ramsar identifies wetlands of international importance, especially those providing waterfowl habitat.

As of 2016, there were 2,231 Ramsar sites, protecting 214,936,005 hectares (531,118,440 acres), and 169 national governments are currently participating.


A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases a river flows into the ground and becomes dry at the end of its course without reaching another body of water. Small rivers can be referred to using names such as stream, creek, brook, rivulet, and rill. There are no official definitions for the generic term river as applied to geographic features, although in some countries or communities a stream is defined by its size. Many names for small rivers are specific to geographic location; examples are "run" in some parts of the United States, "burn" in Scotland and northeast England, and "beck" in northern England. Sometimes a river is defined as being larger than a creek, but not always: the language is vague.Rivers are part of the hydrological cycle; water generally collects in a river from precipitation through a drainage basin from surface runoff and other sources such as groundwater recharge, springs, and the release of stored water in natural ice and snowpacks (e.g., from glaciers). Potamology is the scientific study of rivers, while limnology is the study of inland waters in general. Most of the major cities of the world are situated on the banks of rivers, as they are, or were, used as a source of water, for obtaining food, for transport, as borders, as a defensive measure, as a source of hydropower to drive machinery, for bathing, and as a means of disposing of waste.

Stream bed

A stream bed or streambed is the channel bottom of a stream or river, the physical confine of the normal water flow. The lateral confines or channel margins are known as the stream banks or river banks, during all but flood stage. Under certain conditions a river can branch from one stream bed to multiple stream beds. A flood occurs when a stream overflows its banks and flows onto its flood plain. As a general rule, the bed is the part of the channel up to the normal water line, and the banks are that part above the normal water line. However, because water flow varies, this differentiation is subject to local interpretation. Usually, the bed is kept clear of terrestrial vegetation, whereas the banks are subjected to water flow only during unusual or perhaps infrequent high water stages and therefore might support vegetation some or much of the time.

The nature of any stream bed is always a function of the flow dynamics and the local geologic materials, influenced by that flow. With small streams in mesophytic regions, the nature of the stream bed is strongly responsive to conditions of precipitation runoff. Where natural conditions of either grassland or forest ameliorate peak flows, stream beds are stable, possibly rich, with organic matter and exhibit minimal scour. These streams support a rich biota. Where conditions produce unnatural levels of runoff, such as occurs below roads, the stream beds will exhibit a greater amount of scour, often down to bedrock and banks may be undercut. This process greatly increases watershed erosion and results in thinner soils, upslope from the stream bed, as the channel adjusts to the increase in flow. The stream bed is very complex in terms of erosion. Sediment is transported, eroded and deposited on the stream bed. With global warming there is a fear that the size and shape of riverbeds will change due to increased flood magnitude and frequency. However, one study has shown that the majority of sediment washed out in floods is "near-threshold" sediment that has been deposited during normal flow and only needs a slightly higher flow to become mobile again. This shows that the stream bed is left mostly unchanged in size and shape.Beds are usually what would be left once a stream is no longer in existence; the beds are usually well preserved even if they get buried, because the walls and canyons made by the stream usually have hard walls, usually soft sand and debris fill the bed. Dry stream beds are also subject to becoming underground water pockets (buried stream beds only) and flooding by heavy rains and water rising from the ground and may sometimes be part of the rejuvenation of the stream.

Sustainable gardening

Sustainable gardening includes the more specific sustainable landscapes, sustainable landscape design, sustainable landscaping, sustainable landscape architecture, resulting in sustainable sites. It comprises a disparate group of horticultural interests that can share the aims and objectives associated with the international post-1980s sustainable development and sustainability programs developed to address the fact that humans are now using natural biophysical resources faster than they can be replenished by nature.Included within this compass are those home gardeners, and members of the landscape and nursery industries, and municipal authorities, that integrate environmental, social, and economic factors to create a more sustainable future.

Organic gardening and the use of native plants are integral to sustainable gardening.

Water resources

Water resources are natural resources of water that are potentially useful. Uses of water include agricultural, industrial, household, recreational and environmental activities. All living things require water to grow and reproduce.

97% of the water on the 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.Fresh water is a renewable resource, yet the world's supply of groundwater is steadily decreasing, with depletion occurring most prominently in Asia, South America and North America, although it is still unclear how much natural renewal balances this usage, and whether ecosystems are threatened. The framework for allocating water resources to water users (where such a framework exists) is known as water rights.

Aquatic ecosystems

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