Tidal irrigation

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Tidal irrigation is the subsurface irrigation of levee soils in coastal plains with river water under tidal influence. It is applied in (semi) arid zones at the mouth of a large river estuary or delta where a considerable tidal range (some 2 m) is present. The river discharge must be large enough to guarantee a sufficient flow of fresh water into the sea so that no salt water intrusion occurs in the river mouth.

Irrigation artificial application of water to the land or soil

Irrigation is the application of controlled amounts of water to plants at needed intervals. Irrigation helps to grow agricultural crops, maintain landscapes, and revegetate disturbed soils in dry areas and during periods of less than average rainfall. Irrigation also has other uses in crop production, including frost protection, suppressing weed growth in grain fields and preventing soil consolidation. In contrast, agriculture that relies only on direct rainfall is referred to as rain-fed or dry land farming.

Levee Ridge or wall to hold back water

A levee, dike, dyke, embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels. It is usually earthen and often parallel to the course of a river in its floodplain or along low-lying coastlines.

A coastal plain is flat, low-lying land adjacent to a sea coast. One of the largest coastal plains is located in southeastern United States. The Gulf Coastal Plain of North America extends northwards from the Gulf of Mexico along the Lower Mississippi River to the Ohio River, which is a distance of about 500 miles (800 km).

The irrigation is effectuated by digging tidal canals from the river shore into the main land that will guide the river water inland at high tide.

For the irrigation to be effective the soil must have a high infiltration capacity to permit the entry of sufficient water in the soil to cover the evapotranspiration demand of the crop.

Evapotranspiration

Evapotranspiration (ET) is the sum of evaporation and plant transpiration from the Earth's land and ocean surface to the atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies. Transpiration accounts for the movement of water within a plant and the subsequent loss of water as vapor through stomata in its leaves. Evapotranspiration is an important part of the water cycle. An element that contributes to evapotranspiration can be called an evapotranspirator.

At low tide, the canals and the soil drain out again, which promotes the aeration of the soil.

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Strait A naturally formed, narrow, typically navigable waterway that connects two larger bodies of water

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

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Tidal River (Victoria) perennial river of the West Gippsland catchment, located in the Wilsons Promontory region of the Australian state of Victoria

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Tidal bore A hydrodynamic phenomenon in which the leading edge of the incoming tide forms a wave (or waves) of water that travels up a river or narrow bay against the direction of the river or bays current.

A tidal bore, often simply given as bore in context, is a tidal phenomenon in which the leading edge of the incoming tide forms a wave of water that travels up a river or narrow bay against the direction of the river or bay's current.

Jetty Low bank stretching from the shore into a water span

A jetty is a structure that projects from the land out into water. Often, "jetty" refers to a walkway accessing the centre of an enclosed waterbody. The term is derived from the French word jetée, "thrown", and signifies something thrown out.

Slack water, also known as 'the stand of the tide', is a short period in a body of tidal water when the water is completely unstressed, and there is no movement either way in the tidal stream, and which occurs before the direction of the tidal stream reverses. Slack water can be estimated using a tidal atlas or the tidal diamond information on a nautical chart. The time of slack water, particularly in constricted waters, does not occur at high and low water, and in certain areas, such as Primera Angostura, the ebb may run for up to three hours after the water level has started to rise, and the flood may run for three hours after the water has started to fall. Thornton Lecky, writing in 1884, illustrates the phenomenon with an inland basin of infinite size, connected to the sea by a narrow mouth. Since the level of the basin is always at mean sea level, the flood in the mouth starts at half tide, and its velocity is at its greatest at the time of high water, with the strongest ebb occurring conversely at low water.

Zhengguo Canal canal

The Zhengguo Canal, Zhengguoqu or Chengkuo Canal, named after its designer, Zheng Guo, is a large canal located in Shaanxi province, China. The canal irrigates the Guanzhong plain, north of Xi'an. Together with the Dujiangyan Irrigation System and Lingqu Canal, it is one of the three biggest water conservation projects built before the Qin dynasty in ancient China. The canal connects the Jing river and Luo river, northern tributaries of the Wei River.

Suisun Marsh

Located in northern California the Suisun Marsh is the largest brackish water marsh on west coast of the United States of America. The marsh land is part of the San Francisco Bay tidal estuary, and subject to tidal ebb and flood. The marsh is home to many species of birds and other wildlife, and is formed by the confluence of the Sacramento and San Joaquin rivers between Martinez and Suisun City, California and several other smaller, local watersheds. Adjacent to Suisun Bay, the marsh is immediately west of the legally defined Sacramento-San Joaquin Delta as well as part of the San Francisco Bay estuary.

Couesnon river running from the département of Mayenne in north-western France

The Couesnon is a river running from the département of Mayenne in north-western France, forming an estuary at Mont Saint-Michel. It is 97.8 km (60.8 mi) long, and its drainage basin is 1,124 km2 (434 sq mi). Its final stretch forms the border between the historical duchies of Normandy and Brittany. Its historically irregular course, alternating between two beds on the north and south of the Mont Saint-Michel but eventually definitely settling to the south bed, inspired the saying "The Couesnon in its madness placed the Mont in Normandy", as the Mont is just to the Norman side of the river's current mouth. However, the administrative boundary separating the two regions does not depend on the course of the river, and is about six kilometers west of the Mont.

A tidal river is a river whose flow and level are influenced by tides. A section of a larger river affected by the tides is a tidal reach, although it may sometimes be considered a tidal river if it has been given a separate name. The Brisbane River, which flows into the Pacific Ocean from the east coast of Australia, is also a tidal river.

Rhine–Meuse–Scheldt delta river delta in the Netherlands and Belgium

The Rhine–Meuse–Scheldt delta or Helinium is a river delta in the Netherlands formed by the confluence of the Rhine, the Meuse and the Scheldt rivers. The result is a multitude of islands, branches and branch names that may at first sight look bewildering, especially as a waterway that appears to be one continuous stream may change names as many as seven times, e.g. Rhine → Bijlands Kanaal → Pannerdens Kanaal → Nederrijn → Lek → Nieuwe Maas → Het Scheur → Nieuwe Waterweg. Since the Rhine contributes most of the water, the shorter term Rhine Delta is commonly used. However, this name is also used for the river delta where the Rhine flows into Lake Constance, so it is clearer to call the larger one Rhine–Meuse delta, or even Rhine–Meuse–Scheldt delta, as the Scheldt ends in the same delta. By some calculations, the delta covers 25,347 km2 (9,787 sq mi), making it the largest in Europe.

Irrigation in Iran covers 89,930 km2 making it the fifth ranked country in terms of irrigated area.

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.

Barrage (dam) type of dam

A barrage is a type of low-head, diversion dam which consists of a number of large gates that can be opened or closed to control the amount of water passing through. This allows the structure to regulate and stabilize river water elevation upstream for use in irrigation and other systems. The gates are set between flanking piers which are responsible for supporting the water load of the pool created. The term barrage is borrowed from the French word "barrer" meaning "to bar".

Muthupet Lagoon

Muthupet Lagoon is located at the southern end of the Cauvery river delta on the Bay of Bengal, covering an area of approximately 6,803.01 ha of which only 4% is occupied by well-grown mangroves. The rivers Paminiyar, Koraiyar, Kilaithankiyar, Marakkakoraiyar and other tributaries of the river Cauvery flow through Muthupet and adjacent villages. At the tail end, they form a lagoon before meeting the sea. The northern and western borders of the lagoon are occupied by muddy silt ground which is devoid of mangroves. The mangroves beyond Muthupet lagoon are discontinuously found along the shore and extended up to Point Calimere. Muthupet mangrove forest was under the control of Chatram Department from 1853 to 1912. The Government of the Presidency of Madras Gazette (1937) shows, from 1923 to 1936, half of the revenue obtained from selling mangrove products was paid to the revenue department and the remaining half was spent to maintain the “Chatrams”. The Government declared the Muthupet mangrove forest as revenue forest in February 1937 and accordingly the mangrove forest was handed over to the forest department of the Madras Presidency.

Ennore creek is a backwater located in Ennore, Chennai along the Coromandel Coast of the Bay of Bengal. It is located in the zone comprising lagoons with salt marshes and backwaters, submerged under water during high tide and forming an arm of the sea with the opening to the Bay of Bengal at the creek. The zone is spread over an area of 4 km2, and the creek covers an area of 2.25 km2. It is located 20 km north of the city centre and 2.6 km south of the Ennore Port, and the creek area stretches 3 km into the sea and 5 km along the coast. The creek is nearly 400 m wide, elongated in northeast-southwest direction and merging with the backwater bodies. Once a flourishing mangrove swamp, the creek has been degraded to patches in the fringes mainly due to human activities in the region. The depth of the creek varies from 1 to 2 m and is shallow near the mouth. The north–south trending channels of the creek connect it with the Pulicat Lake to the north and to the distributaries of the Kosasthalaiyar River in the south. The northwestern part of the creek merges with the tidal flats. The soil in the region is of loamy and alluvial types. Most of the area consists of tracts of alluvial soil and the eastern region comprises beach dunes, tidal flats and creek. The creek is oriented from west to east and opens into the Bay of Bengal to the east at Ennore. The creek acts as an outlet for the excess water from the Poondi Reservoir. The creek separates the town of Ennore from the Ennore Port located in the north and the Kattupalli Shipyard located further north. The North Chennai Thermal Power Station is located at the north of the creek and the Ennore Thermal Power Station is located to the south. The creek is part of the Pulicat water system, including the Pulicat lagoon and the Buckingham Canal. As per the 1991 Coastal Regulation Zone notification, the entire Pulicat water system is designated CRZ I. The creek is experiencing siltation due to emergence of the Ennore Port.

Floating dock (impounded)

A floating dock, floating harbour or wet dock is a dock alongside a tidal waterway which maintains a 'constant' level, despite the changing tides.

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