Estuary freshwater inflow is the freshwater that flows into an

estuary 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. Estuaries form a transition zone between river environments and maritime environm ...

. Other types of

environmental flow Environmental flows describe the quantity, timing, and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and well being that depend on these ecosystems. In the Indian context river flows requir ...

s include ''instream flow'', the freshwater water flowing in rivers or streams, and ''estuary outflow'', the outflow from an estuary to the

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

Estuaries

Freshwater inflow: Freshwater flows into an

and mixes with the marine water of the estuarine ecosystem. The mixing of freshwater inflow and the

marine water Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appr ...

of the estuarine ecosystem occurs spatially and temporally from climatic influences including tidal action, seasonal variability and storms. Mixing is affected by the amount of estuarine system. The

tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables ...

s 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. Although estuaries are influenced by the tides, they are often somewhat protected from storms and tidal action by buffers further offshore including

barrier island Barrier islands are coastal landforms and a type of dune system that are exceptionally flat or lumpy areas of sand that form by wave and tidal action parallel to the mainland coast. They usually occur in chains, consisting of anything from ...

s and peninsulas. The low-salinity conditions of the

are created when freshwater mixes with the saltwater of the estuarine system. Average alinityfor freshwater is around 0.5 parts per thousand (ppt) whereas average salinity of the ocean is 35 ppt. 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. In estuaries, primary producers take up

nutrients A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excre ...

such as

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

and

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

. Freshwater inflows carry estuaries, replenishing the stock for phytoplankton use.

Sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

s 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. 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 Ecosystem services are the many and varied benefits to humans provided by the natural environment and healthy ecosystems. Such ecosystems include, for example, agroecosystems, forest ecosystem, grassland ecosystems, and aquatic ecosystems. ...

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. 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 change Global change in broad sense refers to planetary-scale changes in the Earth system. It is most commonly use to encompass the variety of changes connected to the rapid increase in human activities which started around mid-20th century, i.e. the ...

s caused largely by anthropogenic influences, or human impacts, are altering the amount of freshwater inflows to

estuaries 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. Estuaries form a transition zone between river environments and maritime environmen ...

. 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. The removal of freshwater from rivers and streams for anthropogenic use before it reaches the coast is having a negative impact on many

. 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. 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

is becoming a priority worldwide.

Dewatering

Changes in freshwater inflow have resulted in losses of habitat, biodiversity, and productivity. Studies also found changes in bioindicator species community’s biomass correlated with changing freshwater inflows, which indicates secondary production changes with altered inflows. 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

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). In the Mtata Estuary of South Africa, an Estuarine Health Index is used to compare the current state of the

to a predicted reference state. 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. The methodologies for managing freshwater inflow differ slightly but the main goal is to ultimately create or maintain a sustainable

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 Ecosystem-based management is an environmental management approach that recognizes the full array of interactions within an ecosystem, including humans, rather than considering single issues, species, or ecosystem services in isolation. It can be ...

(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. EBM also incorporates data analysis of various interactions over different amounts of time and space. 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. Below are some examples of current

ecosystem-based management Ecosystem-based management is an environmental management approach that recognizes the full array of interactions within an ecosystem, including humans, rather than considering single issues, species, or ecosystem services in isolation. It can be ...

freshwater inflow resources from Texas. Ecosystem-Based Management Freshwater Inflow Resources from Texas

References

* * * * * {{cite book, last=Montagna, first=P.A. , author2=Palmer, T. , author3=Pollack, J., title=Hydrological Changes and Estuarine Dynamics, journal=SpringerBriefs in Environmental Science, year=2013, volume=8, page=94, doi=10.1007/978-1-4614-5833-3, url=https://www.springer.com/life+sciences/ecology/book/978-1-4614-5832-6, isbn=978-1-4614-5832-6 , s2cid=38695060

External links

* http://www.epa.gov/roe/publications.htm Aquatic ecology Rivers