Freshwater inflow

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Environmental flows can be broken down into instream flow, freshwater inflow, and outflow, as shown in the depiction below. Instream flow is the freshwater water flowing in rivers or streams. Freshwater inflow is the freshwater that flows into an estuary. Outflow is the flow from an estuary to the ocean. This article's focus is upon freshwater inflow.

Contents

Estuaries

Freshwater inflow: Freshwater flows into an estuary and mixes with the marine water of the estuarine ecosystem. The mixing of freshwater inflow and the marine water of the estuarine ecosystem occurs spatially and temporally from climatic influences including tidal action, seasonal variability and storms. [1] Mixing is affected by the amount of estuarine system. The tides and the volume of the receiving estuary govern the volume of seawater. Tides are defined as the periodic rise and fall of the surface of the sea along the coast that are driven by the gravitational pull of the moon and of the sun. [2] Although estuaries are influenced by the tides, they are often somewhat protected from storms and tidal action by buffers further offshore including barrier islands and peninsulas. [1]

The low-salinity conditions of the marine water are created when freshwater mixes with the saltwater of the estuarine system. Average [salinity] for freshwater is around 0.5 parts per thousand (ppt) whereas average salinity of the ocean is 35 ppt. [3] The salinity will not be consistent throughout a particular estuary and will be differ from one estuary to the next but its level will range from 0.5 ppt to 35 ppt. [3] In estuaries, primary producers take up nutrients such as nitrogen and phosphorus. [4] Freshwater inflows carry estuaries, replenishing the stock for phytoplankton use. [4] Sediments settling out and form banks, offshore peninsulas, and barrier islands that protect the estuary from strong tidal action and currents. The sediment also supports beaches and provision the inter-tidal wetlands. Organic material delivered to estuaries by freshwater inflows the primary energy source for organisms living in the estuary. [5] Estuarine ecosystems need freshwater inflow to maintain their productivity, or to continue to produce biomass.

Estuarine ecosystems are fundamentally important and necessary to protect through the management of freshwater inflow because of the many ecosystem services they produce. An ecosystem service is something provided by nature that is of value to humans. Estuarine ecosystems are among the most productive ecosystems on the planet. Estuaries house such species as the blue crab, red fish, flounder, spotted seatrout, and many others for some point of the species’ life cycle. Marine habitats, such as those found in estuarine ecosystems, are valued at providing an estimated US14$ trillion worth of ecosystem goods and services annually, or 43% of the global total. [6] Some economically important estuarine habitats include tidal flats, salt marshes, sea grass beds, oyster reefs, and mangroves. This is why estuaries are important to protect and conserve.

Global change

Global changes caused largely by anthropogenic influences, or human impacts, are altering the amount of freshwater inflows to estuaries. [7] Humans are diverting water from rivers and streams, decreasing the amount of flows making it to estuarine ecosystems. Since the 1960s dewatering, or removal of water from streams and rivers, has doubled and around 60% of the Earth’s runoff is captured. [8] The removal of freshwater from rivers and streams for anthropogenic use before it reaches the coast is having a negative impact on many estuaries. Half of the world’s major cities are within 50 km of the coast, and coastal populations are 2.6 times denser than those further inland. [9] Technological advances in the collection of freshwater is continually improving, further straining available freshwater resources. As the human population grows and the strain on water resources continues, the ability to effectively manage freshwater inflows into estuaries is becoming a priority worldwide. [1]

Dewatering

Changes in freshwater inflow have resulted in losses of habitat, biodiversity, and productivity. [10] Studies also found changes in bioindicator species community’s biomass correlated with changing freshwater inflows, which indicates secondary production changes with altered inflows. [11] These studies suggest the health of the estuary depends on freshwater inflow.

Below is an example of how an upstream human diversion creates cascading effects downstream.

Freshwater inflow management

Many different methodologies aimed at freshwater inflow management to maintain an estuary have been implemented throughout the world. Studies are aimed at determining the freshwater inflow amount necessary to maintain an estuarine ecosystem. One common methodology implemented in studies in several U.S. states including Texas, Florida, and California is to indirectly link estuarine resources (i.e. integrity- species composition, biomass, diversity; function- primary production, secondary production, nutrient recycling; sustainability- habitats, valued resources, ecosystem services) to freshwater inflow (i.e. quantity- timing, frequency, duration, extent; quality; tidal connections) through estuarine conditions (i.e. salinity; sediment; dissolved material; particulate material). [1] [12] In the Mtata Estuary of South Africa, an Estuarine Health Index is used to compare the current state of the estuary to a predicted reference state. [13] In the Caloosahatchee Estuary in Florida, the range of inflow that protects key biota, or the animal and plant life of a region, determines the necessary amount of freshwater inflow. [14] The methodologies for managing freshwater inflow differ slightly but the main goal is to ultimately create or maintain a sustainable estuary.

Using ecosystem-based management (EBM) strategies for freshwater inflow oversight

Freshwater inflow management strategies require an all-encompassing approach that incorporates a large amount of data on multiple levels. This type of approach is called an ecosystem-based management strategy. Ecosystem-based management (EBM) strategies require a comprehensive approach to incorporate land, energy, and natural resource use and allocation, involving species management, natural commodities, and humans as components. [15] EBM also incorporates data analysis of various interactions over different amounts of time and space. [16] This may be directed at the maintenance or enhancement of the entire riverine ecosystem, including its various aquatic and riparian biota and components from source to sea. [17] Below are some examples of current ecosystem-based management freshwater inflow resources from Texas.

Ecosystem-Based Management Freshwater Inflow Resources from Texas

ResourcesOrganizationOverview
Freshwater Inflow Tool HRIProvides information for understanding and managing freshwater inflow
TX Environmental Flow Program (SB3)TCEQProvides links to all existing reports regarding freshwater inflow
Senate Bill 3 Nueces BBASC BBASCExplains SB3 process and provides specific Nueces applications (BBEST and BBASC reports)
NERR Science Collaborative MANERRProject to address climate change by helping to establish freshwater inflow requirements
Freshwater Inflows and Estuaries TPWDCase studies of methodologies to estimate changes, impacts, and needs of freshwater inflows
Environmental Flows Information System for Texas CRWRData models and database to determine environmental flow needs

Related Research Articles

Estuary A partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea

An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea.

Lagoon A shallow body of water separated from a larger body of water by barrier islands or reefs

A lagoon is a shallow body of water separated from a larger body of water by barrier islands or reefs. Lagoons are commonly divided into coastal lagoons and atoll lagoons. They have also been identified as occurring on mixed-sand and gravel coastlines. There is an overlap between bodies of water classified as coastal lagoons and bodies of water classified as estuaries. Lagoons are common coastal features around many parts of the world.

Wetland A land area that is permanently or seasonally saturated with water

A wetland is a distinct ecosystem that is flooded by water, either permanently or seasonally, where oxygen-free processes prevail. The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play a number of functions, including water purification, water storage, processing of carbon and other nutrients, stabilization of shorelines, and support of plants and animals. Wetlands are also considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life. Whether any individual wetland performs these functions, and the degree to which it performs them, depends on characteristics of that wetland and the lands and waters near it. Methods for rapidly assessing these functions, wetland ecological health, and general wetland condition have been developed in many regions and have contributed to wetland conservation partly by raising public awareness of the functions and the ecosystem services some wetlands provide.

River delta Silt deposition landform at the mouth of a river

A river delta is a landform created by deposition of sediment that is carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or another river that cannot carry away the supplied sediment. The size and shape of a delta is controlled by the balance between watershed processes that supply sediment, and receiving basin processes that redistribute, sequester, and export that sediment. The size, geometry, and location of the receiving basin also plays an important role in delta evolution. River deltas are important in human civilization, as they are major agricultural production centers and population centers. They can provide coastline defense and can impact drinking water supply. They are also ecologically important, with different species' assemblages depending on their landscape position.

Salt marsh A coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides

A salt marsh or saltmarsh, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is dominated by dense stands of salt-tolerant plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh in trapping and binding sediments. Salt marshes play a large role in the aquatic food web and the delivery of nutrients to coastal waters. They also support terrestrial animals and provide coastal protection.

Narragansett Bay Bay in the state of Rhode Island

Narragansett Bay is a bay and estuary on the north side of Rhode Island Sound covering 147 mi2 (380 km2), 120.5 mi2 (312 km2) of which is in Rhode Island. The Bay forms New England's largest estuary, which functions as an expansive natural harbor and includes a small archipelago. Small parts of it extend into Massachusetts.

Tidal marsh Marsh subject to tidal change in water

A tidal marsh is a marsh found along rivers, coasts and estuaries which floods and drains by the tidal movement of the adjacent estuary, sea or ocean. Tidal marshes experience many overlapping persistent cycles, including diurnal and semi-diurnal tides, day-night temperature fluctuations, spring-neap tides, seasonal vegetation growth and decay, upland runoff, decadal climate variations, and centennial to millennial trends in sea level and climate. They are also impacted by transient disturbances such as hurricanes, floods, storms, and upland fires.

Aquatic ecosystem An ecosystem in a body of water

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.

Yaquina Bay small bay partially within Newport, Oregon, United States

Yaquina Bay is a coastal estuarine community found in Newport, Oregon, United States. Yaquina Bay is a semi-enclosed body of water, approximately 8 km² (3.2 mi²) in area, with free connection to the Pacific Ocean, but also diluted with freshwater from the Yaquina River land drainage. The Bay is traversed by the Yaquina Bay Bridge. There are three small communities that border the Yaquina River and Bay; Newport, Toledo and Elk City. The Yaquina Bay in Newport is a popular tourist destination along the Pacific Coast Highway. It is also an important estuary for the ecology and economy of the area.

Jacques Cousteau National Estuarine Research Reserve

The Jacques Cousteau National Estuarine Research Reserve, located in southeastern New Jersey, encompasses over 110,000 acres (450 km²) of terrestrial, wetland and aquatic habitats within the Mullica River-Great Bay Ecosystem.

St. Lucie River River in the United States of America

The St. Lucie River is a 7-mile-long (11 km) estuary linked to a coastal river system in St. Lucie and Martin counties in the Florida, United States. The St. Lucie River and St. Lucie Estuary are an "ecological jewel" of the Treasure Coast, central to the health and well-being of the surrounding communities. The river is part of the larger Indian River Lagoon system, the most diverse estuarine environment in North America with more than 4,000 plant and animal species, including manatees, oysters, dolphins, sea turtles and seahorses.

Lake Connewarre lake in Victoria, Australia

Lake Connewarre, a shallow estuarine 880-hectare (2,200-acre) lake on the Barwon River, is located on the Bellarine Peninsula southeast of Geelong in the Australian state of Victoria.

Ecology of the San Francisco Estuary

The San Francisco Estuary together with the Sacramento–San Joaquin River Delta represents a highly altered ecosystem. The region has been heavily re-engineered to accommodate the needs of water delivery, shipping, agriculture, and most recently, suburban development. These needs have wrought direct changes in the movement of water and the nature of the landscape, and indirect changes from the introduction of non-native species. New species have altered the architecture of the food web as surely as levees have altered the landscape of islands and channels that form the complex system known as the Delta.

A tidal prism is the volume of water in an estuary or inlet between mean high tide and mean low tide, or the volume of water leaving an estuary at ebb tide.

Eprapah Creek is a sub-tropical stream located in Redland City close to Brisbane in South East Queensland, Australia.

Estuarine water circulation is controlled by the inflow of rivers, the tides, rainfall and evaporation, the wind, and other oceanic events such as an upwelling, an eddy, and storms. Estuarine water circulation patterns are influenced by vertical mixing and stratification, and can affect residence time and exposure time.

Marine habitats A habitat that supports marine life

Marine habitats are habitats that support marine life. Marine life depends in some way on the saltwater that is in the sea. A habitat is an ecological or environmental area inhabited by one or more living species. The marine environment supports many kinds of these habitats.

Tidal barrage dam-like structure used to capture the energy from masses of water

A tidal barrage is a dam-like structure used to capture the energy from masses of water moving in and out of a bay or river due to tidal forces.

Estuarine acidification happens when the pH balance of water in coastal marine ecosystems, specifically those of estuaries, decreases. Water, generally considered neutral on the pH scale, normally perfectly balanced between alkalinity and acidity.While ocean acidification occurs due to the ongoing decrease in the pH of the Earth's oceans, caused by the absorption of carbon dioxide (CO2) from the atmosphere, pH change in estuaries is more complicated than in the open ocean due to direct impacts from land run-off, human impact, and coastal current dynamics. In the ocean, wave and wind movement allows carbon dioxide (CO2) to mixes with water (H2O) forming carbonic acid (H2CO3). Through wave motion this chemical bond is mixed up, allowing for the further break of the bond, eventually becoming carbonate (CO3) which is basic and helps form shells for ocean creatures, and two hydron molecules. This creates the potential for acidic threat since hydron ions readily bond with any Lewis Structure to form an acidic bond. This is referred to as an oxidation-reduction reaction.

Nutrient cycling in the Columbia River Basin involves the transport of nutrients through the system, as well as transformations from among dissolved, solid, and gaseous phases, depending on the element. The elements that constitute important nutrient cycles include macronutrients such as nitrogen, silicate, phosphorus, and micronutrients, which are found in trace amounts, such as iron. Their cycling within a system is controlled by many biological, chemical, and physical processes.

References

  1. 1 2 3 4 Montagna, P.A.; Palmer, T.; Pollack, J. (2013). Hydrological Changes and Estuarine Dynamics. SpringerBriefs in Environmental Science. 8. p. 94. doi:10.1007/978-1-4614-5833-3. ISBN   978-1-4614-5832-6.
  2. ↑ Sumich, J.L. (2004). An Introduction to the Biology of Marine Life, Sixth Edition. Jones and Bartlett Learning. p. 449. ISBN   9780763733131.
  3. 1 2 National Oceanic and Atmospheric Administration (NOAA). "Estuaries". NOAA.
  4. 1 2 D'Elia, C.F.; Sanders, J.G.; Boynton, W.R. (1986). "Nutrient Enrichment Studies in a Coastal Plain Estuary: Phytoplankton Growth in Large-Scale, Continuous Cultures". Canadian Journal of Fisheries and Aquatic Sciences. 43 (2): 397–406. doi:10.1139/f86-050.
  5. ↑ Keith R. Dyer & Robert Joseph Orth (1994). The influence of Atchafalaya River discharge on Fourleague Bay, Louisiana (USA) found in:Changes in Fluxes in Estuaries. Fredensborg, Denmark: Olsen and Olsen. pp. 151–160. ISBN   9788785215222.
  6. ↑ Costanza, R.; d'Arge, R.; de Groot, R.; Farber, S.; Grasso, M.; Hannon, B.; Limburg, K.; Naeem, S.; O'Neill, R. V.; Paruelo, J.; Raskin, R. G.; Sutton, P.; van den Belt, M. (1997). "The Value of the World's Ecosystem Services and Natural Capital" (PDF). Nature. 387 (6630): 253–260. doi:10.1038/387253a0. Archived from the original (PDF) on 2012-07-30.
  7. ↑ "Comparative Analysis of Marine Ecosystems Organization (CAMEO)". CAMEO.
  8. ↑ Crossland, C.J.; et al. (2005). Coastal Fluxes in the Anthropocene. Global Change - the IGBP Series. Berlin, Germany: Springer-Verlag. p. 232. ISBN   978-3-540-27851-1.
  9. ↑ Montagna, P.A.; Kalke, R. D.; Ritter, C. (2002). "Effect of Restored Freshwater Inflow on Macrofauna and Meiofauna in Upper Rincon Bayou, Texas, USA". Estuaries. 25 (6): 1436–1447. doi:10.1007/bf02692237. JSTOR   1352870.
  10. ↑ Kim, H. C.; Montagna, P. A. (2009). "Implications of Colorado River Freshwater Inflow to Benthic Ecosystem Dynamics: A Modeling Study". Estuarine, Coastal and Shelf Science . 83 (4): 491–504. doi:10.1016/j.ecss.2009.04.033.
  11. ↑ Alber, Merryl (December 2002). "A Conceptual Model of Estuarine Freshwater Inflow Management" (PDF). Estuaries. 25 (6B): 1246–1261. doi:10.1007/bf02692222.
  12. ↑ Adams, J.B.; Bate, C. G.; Harrison, T.D.; Huizinga, P.; Taljaard, S.; Niekerk, L. V.; Plumstead, E. E.; Whitfield, A.K.; Wooldridge, T. H. (December 2002). "Estuaries and Application to the Mtata Estuary, South Africa". Estuaries. 25 (6B): 1382–1393. doi:10.1007/bf02692232.
  13. ↑ Chamberlain, R.H.; Doering, P.H. (1998). "Preliminary Estimate of Optimum Freshwater Inflow to the Caloosahatchee Estuary: A Resource Based Approach. In S. F. Treat (ed.), Proceedings of the 1997 Charlotte Harbor Public Conference and Technical Symposium" (PDF). South Florida Water Management District and Charlotte Harbor National Estuary Program. Technical Report No. 98-02: 121–130. Archived from the original (PDF) on 2010-06-17.
  14. ↑ Arkema, K.K.; Abramson, S.C.; Dewsbury, B.M. (2006). "Marine Ecosystem-Based Management: From Characterization to Implementation" (PDF). Frontiers in Ecology and the Environment. 4 (10): 525–532. doi:10.1890/1540-9295(2006)4[525:memfct]2.0.co;2.
  15. ↑ Hutchison, L.M. (2011). Master's Thesis: Stakeholder Perceptions of Ecosystem Services of Coastal Habitats. Corpus Christi, TX: Texas A&M University- Corpus Christi. p. 107.
  16. ↑ Tharme, R.E. (2003). "A Global Perspective on Environmental Flow Assessment: Emerging Trends in the Development and Application of Environmental Flow Methodologies for Rivers". River Research and Applications. 19 (5–6): 397–441. doi:10.1002/rra.736.
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