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Canal

Canal

, France]] France] Canals are man-made waterways, usually connecting existing lakes, rivers, or oceans. Irrigation canals are man-made waterways for the delivery of water and preceded the use of transportation canals used by barges or narrowboats on smaller canals, and by ships on ship canals that connect to the ocean. The oldest-known canals were built in Mesopotamia, c. 4000 BC. Ancient canals in the West were dwarfed by the Grand Canal of China, the longest canal built in ancient times. In Europe and then in the young United States, inland canals preceded the development of railroads during the earliest phase of the Industrial Revolution; some canals were later drained and used as railroad rights-of-way. Navigable canals reached into previously isolated areas and brought them in touch with the world economy. The Erie Canal, for instance, opened up a connection from the populated Northeast to the fertile Great Plains. Erie Canal] The pace of draining of fenland and polder in the Low Countries quickened in the 14th century and canalization made the village of Amsterdam a port. Canals are so deeply identified with Venice that many cities that have canals used as waterways have been called "the Venice of..." Some rivers have also been 'canalised' to make them navigable. Competition from the railroad network made many canals obsolete for commercial transportation, and many fell into decay. A movement that began in Britain and France to use the picturesque early industrial canals for pleasure boats has spurred rehabilitation of stretches of historic canals. Canals have found another use in the 21st century, as wayleaves for fibre optic telecommunications networks.

Miscellaneous

For a time in the early 20th century, it was believed that there were canals on Mars. canals on Mars

Famous canals and lists

- List of waterways
- Canals of Ireland
- List of canals in the United States
- Canals of the United Kingdom
- Suez Canal
- Panama Canal
- Corinth Canal
- Venice
- Amsterdam
- Welland Canal - Central Canada
- Saint Lawrence Seaway - Quebec, Ontario, Canada
- Rideau Canal - Ottawa, Ontario, Canada
- Shubie Canal - Nova Scotia, Canada

Lake

A Lake is a body of water surrounded by land. The majority of lakes are fresh water, and most lie in the northern hemisphere at higher latitudes. Large lakes are sometimes referred to as "inland seas" and small seas are sometimes referred to as lakes. The term lake is also used to describe a feature such as Lake Eyre, which is dry most of the time but becomes filled under seasonal conditions of heavy rainfall. Many lakes are artificial and are constructed for hydro-electric power supply, recreation (swimming, wind surfing,...), water supply, etc. Finland is known as The Land of the Thousands Lakes (actually there are 187,888 lakes in Finland, 60,000 of them are big ones) and Minnesota is known as The Land of Ten Thousand Lakes. The Great Lakes of North America originated in the ice age. Over 60% of the world's lakes are in Canada; this is because of the deranged drainage system that dominates the country.

Origin of natural lakes

Most lakes are young, as the natural results of erosion will tend to wear away one of the basin sides containing the lake. There are a number of natural processes that can form lakes. A recent tectonic uplift of a mountain range can create bowl-shaped depressions that accumulate water and form lakes. The advance and retreat of glaciers can scrape depressions in the surface where lakes accumulate. Such lakes are common in Scandinavia, Siberia and Canada. Lakes can also form by means of landslides or by glacial blockages. An example of the latter occurred during the last ice age in the state of Washington, when a huge lake formed behind a glacial flow. When the ice retreated, the result was an immense flood that created the Dry Falls Monument at Sun Lakes, Washington. Saline lakes can form where there is no natural outlet or the water evaporates rapidly, and the drainage surface of the water table has a higher than normal salt content. Examples of salt lakes include the Great Salt Lake, the Caspian Sea and the Dead Sea. Small, crescent-shaped lakes called oxbow lakes can form in river valleys as the result of meandering. The slow-moving river forms a sinuous shape as the outer side of bends is torn away more rapidly than the inner side. Eventually a horseshoe bend is formed and the river cuts through the narrow neck. This gap now forms the main passage for the river and the ends of the bend become silted up. Lake Vostok is an under-ice lake in Antarctica, possibly the largest in the world. The pressure from ice and the internal chemical composition means that if the lake were drilled into, it may result in a fissure and spraying in the same manner as a shaken can of soda. Some lakes, like Lake Baikal and Lake Tanganyika are volcanic in origin, and lie on geological fault lines. The Crater Lake in Oregon is a lake located within the caldera of an extinct volcano. Some lakes come into existence as a result of sinkhole activity.

Characteristics

The change in level of a lake is controlled by the difference between the sources of inflow and outflow, compared to the total volume of the lake. The significant input sources are precipitation onto the lake; runoff carried by streams and channels from the lake's catchment area; groundwater channels and aquifers, and man-made sources from outside the catchment area. Output sources are evaporation from the lake; surface and groundwater flows, and any extraction of lake water by humans. As climate conditions and human water requirements vary, these will create fluctuations in the lake level. Lakes can be categorized on the basis of their richness of nutrients, which typically effects plant growth. Nutrient poor lakes are said to be oligotrophic, and are generally clear, having a low concentration of plant life. Mesotropic lakes have good clarity and an average level of nutrients. Eutrophic lakes are enriched with nutrients, resulting in good plant growth and possible algal blooms. A hypertrophic lake is a water body that has been highly enriched with nutrients. These lakes typically have poor clarity and are subject to algal blooms. Lakes typically reach this condition due to human activities, such as heavy use of fertilizers in the lake catchment area. Such lakes are of little use, and have a poor ecosystem.

Types of lakes

A periglacial lake is one in which part of its margin is formed by an ice sheet, ice cap or glacier, the ice having obstructed the natural drainage of the land. A subglacial lake is one which is permanently covered by ice. They can occur under glaciers and ice caps or ice sheets. There are many such lakes, but Lake Vostok in Antarctica is by far the largest. The are kept liquid because the overlying ice acts as a thermal insulator retaining energy introduced to its underside by friction, water percolating through crevasses, by the pressure from the mass of the ice sheet above or by geothermal heating below. Because of the unusual relationship between water's temperature and its density, the water in lakes in temperate climates mixes twice a year. Fresh water is most dense at about 4 degrees Celsius. When the temperature of the water at the surface of a lake reaches the temperature at which water is most dense all the water in the lake can mix, bringing oxygen starved water up from the depths, and bringing oxygen down to decomposing sediments. When the density of surface water differs from that of the deeper water there is a marked barrier layer, the thermocline, that prevents mixing. Deep Temperate lakes can maintain a reservoir of cold water year-round. The reservoir of deep, cold water allows cities to tap that reservoir for deep lake water cooling. Since the water of deep tropical lakes never reaches the temperature where water reaches its maximum density, there is no process that makes the water mix. The deeper layer becomes oxygen starved, and can become saturated with carbon dioxide, and possibly other gases, like sulfur dioxide, if there is even a trace of volcanic activity. Exceptional events, like earthquakes or landslides, which do cause mixing, that brings up the deep layers, can release a vast cloud of toxic gas. The amount of gas that can be dissolved in water is pressure related. As the water surfaces, and the pressure drops, a vast amount of gas cab comes out of solution. Under these circumstances even carbon dioxide is toxic. Carbon dioxide is heavier than air, and the released carbon dioxide flows down the river valley.

Artificial lakes

A reservoir (French: réservoir) is an artificial lake created by flooding land behind a dam. Some of the world's largest lakes are reservoirs. Artificial lakes can also be made deliberately by digging one or by flooding an open-pit mine.

Abiotic and biotic limnology

mine Limnology divides lakes in three zones: littoral zone, which is a sloped area that is close to land; open-water zone, where sunlight is abundant; and deep-water zone, where little sunlight can reach. The depth which light can reach in lakes depends on the density and motion of particles. These particles can be sedimentary or biological in origin and are responsible for the color of the water. Decaying plant matter for instance is responsible for a yellow or brown color, while algae result in greenish water. In very shallow water bodies, iron oxides make water reddish brown. Biological particles are algae and detritus. A sediment particle is in suspension if its weight is less than the random turbidity forces acting upon it. The turbidity is a decisive factor in the transparency of the water. Bottom-dwelling detritivorous fish are responsible for turbid waters, because they stir the mud in search for food. Piscivorous fish eat plant-eating (planktonivorous) fish, thus increasing the number of algae (see aquatic trophic cascade). The light depth or transparency is measured by using a Secchi disk. This is a 20 cm disk with alternating white and black quadrants. The depth at which the disk is no longer visible, is the Secchi depth, and is a measure for transparency. It is commonly used to test eutrophication. A lake moderates the surrounding region's temperature and climate because water has a very high specific heat capacity (4186). In the daytime, the lake can cool the land beside it with local winds, resulting in a sea breeze; in the night, it can warm it, forming a land breeze.

How lakes disappear

A lake may be infilled with deposited sediment, and gradually, the lake becomes a wetland, such as a swamp or marsh. An important difference exists between lowland and highland lakes: lowland lakes are more placid, are less rocky/more sedimentary, have a less sloping bottom, and generally contain more plant life. Large water plants (typically reeds) accelerate this closing process significantly because they trap sediment. Turbid lakes, and lakes with much plant-eating fish, tend to disappear slower. A "disappearing" lake (barely noticeable on a human timescale) typically has a water's edge with extensive plant mats. They become a new habitat for other plants (like peat moss, when conditions are right) and animals, many of which are very rare. Gradually, the lake closes, and young peat may form, forming a fen. In lowland river valleys (allowing the river to meander), the presence of peat is explained by the closing of historical oxbow lakes. In the very last stages of succession, more trees would grow in, eventually turning the wetland into a forest. Some lakes can also disappear seasonally; they are called Intermittent lakes and are typical of karstic terrain. A prime example of this is Lake Cerknica in Slovenia. On June 3, 2005 in Bolotnikovo, Russia, a lake called White Lake vanished in a short period of time (minutes). News sources reported government officials theorized that this strange phenomena may have been caused by a shift on soil underneath the lake which drained water to channels leading to Oka River. Neusiedler See, located in Austria and Hungary, dried up several times for a of number years during the past centuries. As of 2005, it is again rapidly losing water, giving rise to the fear that it will be completely dried up by 2010.

Extraterrestrial lakes

At present the surface of the planet Mars is too cold to permit pooling of liquid water on the surface. However geologic evidence appears to confirm that ancient lakes once formed on the surface. It is also possible that volcanic activity on Mars will occasionally melt the subsurface ice, forming large lakes. Under current conditions this water will quickly evaporate or freeze unless insulated in some manner, such as by a coating of volcanic ash. Jupiter's small moon Io is volcanically active due to tidal stresses, and as a result sulfur deposits have accumulated on the surface. Some photographs taken during the Galileo mission appear to show lakes of liquid sulfur on the surface. There are dark basaltic plains on the Moon, similar to lunar maria but smaller, that are called lacus (singular lacus, Latin for "lake"). They were once thought by early astronomers to be literal lakes.

Notable lakes

- The largest lake in the world by surface area is the Caspian Sea. With a surface area of 394,299 sq. km., it has a surface area greater than the next six largest lakes combined.
- The largest freshwater lake, and second largest lake altogether is Lake Superior with a surface area of 82,414 sq. km. It is also the largest lake in North America and is a part of the Great Lakes.
- The deepest lake is Lake Baikal in Siberia, with a bottom at 1,741 m (5,712 ft.) and is the world's largest freshwater lake by volume.
- The highest navigable lake is lake Titicaca, at 3821 m above sea level. It is also the second largest lake in South America.
- The world's highest lake is Lhagba Pool in Tibet at 6,368 m.
- The world's lowest lake is the Dead Sea, at 396 m (1,302 ft.) below sea level. It is also the lake with the highest salt concentration.
- The largest freshwater-lake island is Manitoulin Island on Lake Huron, with a surface area of 2,766 square km.
- The largest lake located on an island is Nettilling Lake on Baffin Island.
- Lake Toba on the island of Sumatra is located in what is probably the largest resurgent caldera on Earth.
- The largest freshwater lake in Europe is Lake Balaton, followed by Lake Geneva.
- Lake Victoria is the largest lake in Africa. It is a part of the Great Lakes of Africa.
- Lake Maracaibo is the largest lake in South America. Lake Titicaca is the largest freshwater lake in South America.
- The largest lake located completely within the boundaries of a single city is Lake Wanapitei in the city of Greater Sudbury, Ontario, Canada. Before the current city boundaries came into effect in 2001, this status was held by Lake Ramsey, also in Sudbury.
- Saimaa is the largest lake in Finland (the land of 187,888 lakes).

External links

- [http://www.highestlake.com/ Lists of the highest lakes in the US and the world]
- [http://www.mlswa.org/lkclassif1.htm Lake Classification Systems]
- [http://www.uklakes.net/ UKLakes Database]
- [http://www.midwestlakes.org/ Midwest Lakes Policy Center] Category:Bodies of water Category:Landforms ko:호수 ja:湖 simple:Lake th:ทะเลสาบ

Ocean

:For other uses see Ocean (disambiguation) Ocean (disambiguation)] Ocean (from Okeanos, Greek for river, the ancient Greeks noticed that a strong current flowed off Gibraltar, and assumed it was a great river); covers almost three quarters (71%) of the surface of the Earth, and nearly half of the world's marine waters are over 3000 m deep. This global, interconnected body of salt water, called the World Ocean, is divided by the continents and archipelagos into the following four bodies, from the largest to the smallest: the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, and the Arctic Ocean, and, according to some authorities such as International Hydrographic Organization(IHO), a fifth ocean, the Southern Ocean. Some geographers and some governments but not the US, recognize the IHO as defining official water body names and boundaries. (The US authority is the United States Board on Geographic Names.) The IHO officially sanctioned the Southern Ocean name only in 2000, but its definition by a line of latitude (with IHO members widely disputing which line of latitude) has left its acceptance as a fifth ocean open to question. The National Geographic Society and some other leading geographers and cartographers continue to use "South Pacific", "South Atlantic", and "Indian" Ocean for the waters around Antarctica. A few Oceanographers recognize only four oceans also, treating the Arctic Ocean (or the Arctic Sea) as a part of the Atlantic Ocean. Smaller regions of the oceans are called seas, gulfs, straits and other names. Geologically, an ocean is an area of oceanic crust covered by water. Oceanic crust is the thin layer of solidified volcanic basalt that covers the Earth's mantle where there are no continents. From this point of view, there are three "oceans" today: the World Ocean, and the Black and Caspian Seas that were formed by the collision of Cimmeria with Laurasia. The Mediterranean Sea is very nearly its own "ocean", being connected to the World Ocean through the Strait of Gibraltar, and indeed several times over the last few million years movement of the African Continent has closed the strait off entirely, making the Mediterranean a fourth "ocean". (The Black Sea is connected to the Mediterranean through the Bosporus, but this is in effect a natural canal, cut through continental rock some 7000 years ago, rather than a piece of oceanic sea floor like the Strait of Gibraltar.) The area of the World Ocean is 361 million km², its volume is 1370 million km³, and its average depth is 3790 m. Nearly half of the world's marine waters are over 3000 m deep. This does not include seas not connected to the World Ocean, such as the Caspian Sea. The total mass of the hydrosphere is about 1.4 × 10²¹ kg, ca. 0.023 % of the Earth's total mass. See sea water for a detailed discussion of ocean water composition, most notably its salinity.

Origins

The Oceans of the world most likely originated by comets striking the Earth.

Exploration

salinity Travel on the surface of the ocean through the use of boats dates back to prehistoric times, but only in modern times has extensive underwater travel become possible. The deepest point in the ocean is the Mariana Trench located in the Pacific Ocean near the Northern Mariana Islands. It has a maximum depth of 10,923 m (35,838 ft) [http://www.rain.org/ocean/ocean-studies-challenger-deep-mariana-trench.html]. It was fully surveyed in 1951 by the British naval vessel, "Challenger II" which gave its name to the deepest part of the trench, the "Challenger Deep". Much of the bottom of the world's oceans is unexplored and unmapped. A global image of many underwater features larger than 10 km was created in 1995 based on gravitational distortions of the nearby sea surface.

Climate

One of the most dramatic forms of weather occurs over the oceans: tropical cyclones (also called "typhoons" and "hurricanes" depending upon where the system forms). Ocean currents greatly affect Earth's climate by transferring warm or cold air and precipitation to coastal regions, where they may be carried inland by winds. The Antarctic Circumpolar Current encircles that continent, influencing the area's climate and connecting currents in several oceans.

Ecology

The oceans are home to the majority of plant and animal life on Earth. These lifeforms include:
- fish
- cetacea such as whales, dolphins and porpoises,
- cephalopods such as the octopus
- crustaceans such as lobsters and shrimp
- marine worms
- plankton
- krill

Economy

The oceans are essential to transportation: a huge portion of the world's goods are moved by ship between the world's seaports. Important ship canals include the Saint Lawrence Seaway, Panama Canal, and Suez Canal.

Ancient oceans

Continental drift has reconfigured the Earth's oceans, joining and splitting ancient oceans to form the current oceans. Ancient oceans include:
- Panthalassa, the vast world ocean that surrounded the Pangaea supercontinent.
- Tethys Ocean, the ocean between the ancient continents of Gondwana and Laurasia.
- Iapetus Ocean, the southern hemisphere ocean between Baltica and Avalonia.

Ocean rowing

Extraterrestrial oceans

Earth is the only known planet with liquid water on its surface, and is certainly the only such in our own solar system. However, liquid water is thought to be present under the surface of several natural satellites, particularly the Galilean moons of Europa, and, with less certainty, its fellows Callisto and Ganymede. Other icy moons may have once had internal oceans that have now frozen, such as Triton. The planets Uranus and Neptune may also possess large oceans of liquid water under their thick atmospheres, though their internal structure is not well understood at this time. There is currently much debate over whether Mars once had an ocean of water in its northern hemisphere, and over what happened to it if it did; recent findings by the Mars Exploration Rover mission indicate it had some long-term standing water in at least one location, but its extent is not known. Liquid hydrocarbons are thought to be present on the surface of Titan, though it may be more accurate to describe them as "lakes" rather than an "ocean". The distribution of these liquid regions will hopefully be better known after the full analysis of data from the Huygens probe of the Cassini-Huygens space mission, which dropped onto Titan's surface in January 2005. Titan is also thought likely to have a subterranean water ocean under the mix of ice and hydrocarbons that forms its outer crust.

Oceans in film

- In the movie Muppet Treasure Island, a non-specific ocean is featured, and referred to as the "Big Blue Wet Thing". Oceans have also been featured in many other movies such as Free Willy. To list more, click edit beside "Oceans on Film"

External links

- [http://www.oceanexplorer.noaa.gov/ Ocean Explorer] - An educational and reference resource from NOAA
- [http://news.bbc.co.uk/2/hi/science/nature/4033555.stm Science taps into ocean secrets]
- [http://www.palomar.edu/oceanography/salty_ocean.htm Why is the ocean salty?]
- [http://ioc.unesco.org/oceanteacher/resourcekit/M3/Formats/Geography/OceansSeas.htm Official IHO boundaries of Oceans and Seas]
- [http://www.thehydrogenexpedition.com The Hydrogen Expedition] The first circumnavigation of the globe in a hydrogen fuel cell powered boat
- [http://www.coreocean.org Coreocean]
- [http://www.nopp.org/ NOPP - The National Oceanographic Partnership Program] Category:Bodies of water Category:Oceanography zh-min-nan:Hái-iûⁿ ko:대양 ms:Lautan ja:大洋 simple:Ocean th:มหาสมุทร

Irrigation

] Irrigation (in agriculture) is the replacement or supplementation of rainfall with water from another source in order to grow crops. In contrast, agriculture that relies only on direct rainfall is sometimes referred to as dryland farming.

Overview

The water source for irrigation may be a nearby or distant body of liquid or frozen water such as a river, spring, lake, aquifer, well, or snowpack. Depending on the distance of the source and the seasonality of rainfall, the water may be channelled directly to the agricultural fields or stored in reservoirs or cisterns for later use. In addition, the "harvesting" of local rain that falls on the roofs of buildings or on nearby unfarmed hills and its use to supplement the rain that falls directly on farmed fields also involves irrigation. Various types of irrigation techniques differ in how the water obtained from the source is distributed within the field. In general, the goal is to supply the entire field uniformly with water, so that each plant has the amount of water it needs, neither too much nor too little.

Types of irrigation

Flood (furrow) irrigation

Ditches can be dug with hand tools, turned with a plow pulled by an animal or tractor, or precisely fashioned using laser-guided instruments depending on economic and physical factors such as the size of the field, the types of technology available, and the cost of manpower. Plants are grown in raised beds or listed rows. Water is distributed throughout the field via canals, unlined ditches, or furrows, between the rows or beds by use of rigid gated plastic or aluminum pipe, layflat plastic with holes punched at each furrow, concrete or plastic lined ditches, or unlined ditches. Where ditches are used, siphon tubes move water from the main ditch to the furrow. When pipes are used, water flow can be controlled by turning it on or off at the local source or by using automatic or manually controlled gates to transfer it from one set of ditches to another. Unless the field is small or very level, parts of it may suffer from water-logging while other parts may be too dry. Depending on heat, wind, and soil permeability, much water may be lost before it can benefit the plants. Automatic valves, also known as surge valves, can increase the efficiency of furrow irrigation because they alternately wet the furrows and allow the soil infiltration rate to slow prior to using the furrow for actual irrigation. Once common in the United States, many ditch irrigation systems have been replaced because of high labor costs and increasing demands on water resources. Furrow irrigation also has a tendency to raise the water table in some areas and cause soil salination, requiring drainage. These types of systems are still common in other parts of the world.

Terracing

Terracing is a form of irrigation in which large steps are cut into hillsides and supported by stone or concrete walls. The level parts are used as garden plots or small fields. As water flows down the hillside it is channelled to each plot (probably most often by ditch irrigation). Terracing is usually very labor-intensive, since fields are small and access to them may be steep and narrow making it difficult to mechanize the work. In addition, the walls need constant maintenance, especially in rainy climates. However, terracing does allow steep mountainsides to be used to grow plants (although it may be more cost-effective to use them only for animal pasturage).

Overhead (sprinkler) irrigation

animal pasturage]] In overhead or sprinkler irrigation, water is piped to one or more central locations within the field and distributed by overhead high-pressure sprinklers or guns or by lower-pressure sprays. A system utilizing sprinklers, sprays, or guns mounted overhead on permanently installed risers is often referred to as a solid-set irrigation system. Some sprinklers can also be hidden below ground level, if aesthetics is a concern, and pop up in response to increased water pressure. This type of system is commonly used in lawns, golf courses, cemeteries, parks, and other turf areas. Sprinklers that spray in a fixed pattern are generally called sprays or spray heads. Sprays are not usually designed to operate at pressures above 30 lbf/in² (200 kPa), due to misting problems that may develop. Higher pressure sprinklers that rotate are called rotors and are driven by a ball drive, gear drive, or impact mechanism. Rotors can be designed to rotate in a full or partial circle. Guns are similar to rotors, except that they generally operate at very high pressures of 40 to 130 lbf/in² (275 to 900 kPa) and flows of 50 to 1200 US gal/min (3 to 76 L/s), usually with nozzle diameters in the range of 0.5 to 1.9 inches (10 to 50 mm). Guns are used not only for irrigation, but also for industrial applications such as dust suppression and logging. Sprinklers may also be mounted on movable platforms connected to the water source by a hose. At the high-tech end, computerized, automatically moving wheeled systems may irrigate large areas unattended. At the low end, such as in a small greenhouse or landscape, a person may be watering each plant individually with a hose end sprinkler or even a watering can. One drawback of overhead irrigation is that much water can be lost because of high winds or evaporation, and irrigating the entire field uniformly can be difficult or tedious if the system is not properly designed. Water remaining on plants' leaves may promote fungal and other diseases. If fertilizers are included in the irrigation water, plant leaves can be burned, especially on hot, sunny days. Overhead irrigation is generally the best solution for watering lawns and golf courses, although drip irrigation is gaining in popularity in some lawn applications. (See also center pivot irrigation.) Manually assembled systems of piping that are broken down to permit tillage and harvesting are sometimes called "hand set" or "hand move pipe". These are also commonly used on athletic fields where permanently installed sprinklers or outlets are not desired or where low initial costs are a factor. harvesting

Center pivot irrigation

Central pivot irrigation is a form of overhead irrigation consisting of several segments of pipe (usually galvanized steel or aluminum) joined together and supported by trusses, mounted on wheeled towers with sprinklers positioned along its length. The system moves in a circular pattern and is fed with water from the pivot point at the center of the arc. These systems are common in parts of the United States where terrain is flat. Most center pivot systems now have drops hanging from a u-shaped pipe called a gooseneck attached at the top of the pipe with sprinkler heads that are positioned a few feet (at most) above the crop, thus limiting evaporative losses. Drops can also be used with drag hoses or bubblers that deposit the water directly on the ground between crops. The crops are planted in a circle to conform to the center pivot. This type of system is known as LEPA (Low Energy Precision Application). Low Energy Precision Application Originally, most center pivots were water powered. These were replaced by hydraulic systems (T-L) and electric motor driven systems (Lindsay, Reinke, Valley). Most systems today are driven by an electric motor mounted at each tower. Center pivot equipment can also be configured to move in a straight line, where the water is pulled from a central ditch. In this scenario, the system is called a linear move irrigation system.

Lateral move (Side roll, Wheel line) irrigation

A series of pipes, each with a wheel of about 1.5 m diameter permanently affixed to its midpoint and sprinklers along its length, are coupled together at one edge of a field. Water is supplied at one end using a large hose. After sufficient water has been applied, the hose is removed and the remaining assembly rotated either by hand or with a purpose-built mechanism, so that the sprinklers move 10m across the field. The hose is reconnected. The process is repeated until the opposite edge of the field is reached. This system is less expensive to install than a center pivot, but much more labor intensive to operate, and it is limited in the amount of water it can carry. Most systems utilize 4 or 5 inch diameter aluminum pipe. One feature of a lateral move system is that it consists of sections that can be easily disconnected. They are most often used for small or oddly-shaped fields, such as those found in hilly or mountainous regions, or in regions where labor is inexpensive.

Drip, or trickle irrigation

Low Energy Precision Application :See main article at drip irrigation Water is delivered at or near the root zone of plants, drop by drop. This type of system can be the most water-efficient method of irrigation, if managed properly, since evaporation and runoff are minimized. In modern agriculture, drip irrigation is often combined with plastic mulch, further reducing evaporation, and is also the means of delivery of fertilizer. The process is known as fertigation. Deep percolation, where water moves below the root zone, can occur if a drip system is operated for too long of a duration. Drip irrigation methods range from very high-tech and computerized to low-tech and relatively labor-intensive. Lower water pressures are usually needed than for most other types of systems, with the exception of low energy center pivot systems and surface irrigation systems, and the system can be designed for uniformity throughout a field or for precise water delivery to individual plants in a landscape containing a mix of plant species. Although it is difficult to regulate pressure on steep slopes, pressure compensating emitters are available, so the field does not have to be level. High-tech solutions involve precisely calibrated emitters located along lines of tubing that extend from a computerized set of valves. Both pressure regulation and filtration to remove particles are important. The tubes are usually black (or buried under soil or mulch) to prevent the growth of algae and to protect the polyethylene from degradation due to ultraviolet light. But drip irrigation can also be as low-tech as a porous clay vessel sunk into the soil and occasionally filled from a hose or bucket. Subsurface drip irrigation has been used successfully on lawns, but it is more expensive than a more traditional sprinkler system. Surface drip systems are not cost-effective (or esthetically pleasing) for lawns and golf courses.

Subirrigation

Used in commercial greenhouse production, usually for potted plants, water is delivered from below, absorbed upwards, and the excess collected for recycling. Typically, a solution of water and nutrients floods a container or flows through a trough for a short period of time, 10-20 minutes, and is then pumped back into a holding tank for reuse. Subirrigation requires fairly sophisticated, expensive equipment and management. Advantages are water and nutrient conservation, and labor-saving through lowered system maintenance and automation. It is similar in principle and action to subsurface drip irrigation. The same concept of subsurface flooding and drainage is also being experimented with as an outdoor subirrigation method.great system of irrigation is on indus river

How an irrigation system works

Most commercial and residential irrigation systems are "in ground" systems, which means that everything is buried in the ground. With the pipes, sprinklers, and irrigation valves being hidden, it makes for a cleaner, more presentable landscape without garden hoses or other items having to be moved around manually. The beginning of a sprinkler system is the water source. This is usually a tap into an existing (city) water line or a pump that pulls water out of a well or a pond.

History of irrigation

Evidence exists of irrigation in Mesopotamia and Egypt as far back as the 6th millennium BC. There is also evidence of ancient Egyptian pharaohs of the twelfth dynasty using the natural lake of the Fayûm as a reservoir to store surpluses of water for use during the dry seasons, as the lake swelled annually as caused by the annual flooding of the Nile. Ancient visitors reported the appearance of "an artificial excavation, as reported by classic geographers and travellers" ([http://www.newadvent.org/cathen/05329b.htm CATHOLIC ENCYCLOPEDIA: Egypt: I. GENERAL DESCRIPTION: Flora and Agriculture]). In the Zana Valley of the Andes Mountains in Peru, archaeologists found remains of 3 irrigation canals radiocarbon dated from the 4th millennium BC, the 3rd millennium BC and the 9th century. These canals are the earliest record of irrigation in the New World. Traces of a canal possibly dating from the 5th millennium BC were found under the 4th millenium canal.(Dillehay, et al., 2005) By the middle of the 20th century, the advent of diesel and electric motors led for the first time to systems that could pump groundwater out of major aquifers faster than it was recharged. This can lead to permanent loss of aquifer capacity, decreased water quality, ground subsidence, and other problems. The future of food production in such areas as the North China Plain, the Punjab, and the Great Plains of the US is threatened.

Problems in irrigation

- Competition for surface water rights.
- Depletion of underground aquifers.
- Ground subsidence (e.g. New Orleans, Louisiana)
- Buildup of toxic salts on soil surface in areas of high evaporation.

References

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- PMID 16284247

External links

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- Category:Agriculture Category:Agronomy Category:Water Category:Environmental science ja:灌漑 simple:Irrigation

Transport

:For other article subjects named transport, see Transport (disambiguation). Transportation redirects here, for other uses, see Transportation (disambiguation). Transport or transportation is the movement of people, goods, signals and information from one place to another. The term is derived from the Latin trans ("across") and portare ("to carry").

Aspects of transport

The field of transport has several aspects: loosely they can be divided into a triad of infrastructure, vehicles, and operations. Infrastructure includes the transport networks (roads, railways, airways, canals, pipelines, etc.) that are used, as well as the nodes or terminals (such as airports, railway stations, bus stations and seaports). The vehicles generally ride on the networks, such as automobiles, bicycles, buses, trains, airplanes. The operations deal with the control of the system, such as traffic signals and ramp meters, railroad switches, air traffic control, etc, as well as policies, such as how to finance the system (for example, the use of tolls or gasoline taxes). Broadly speaking, the design of networks are the domain of civil engineering and urban planning, the design of vehicles of mechanical engineering and specialized subfields such as nautical engineering and aerospace engineering, and the operations are usually specialized, though might appropriately belong to operations research or systems engineering.

Modes of transport

Modes are combinations of networks, vehicles, and operations, and include walking, the road transport system, rail transport, ship transport and modern aviation.

Transport and communications

Transport and communication are both substitutes and complements. Though it might be possible that sufficiently advanced communication could substitute for transport, one could telegraph, telephone, fax, or email a customer rather than visiting them in person, it has been found that those modes of communication in fact generate more total interactions, including interpersonal interactions. The growth in transport would be impossible without communication, which is vital for advanced transportation systems, from railroads which want to run trains in two directions on a single track, to air traffic control which requires knowing the location of aircraft in the sky. Thus, it has been found that the increase of one generally leads to more of the other.

Transport and land use

There is a well-known relationship between the density of development, and types of transportation. Intensity of development is often measured by area of Floor Area Ratio (FAR), the ratio of useable floorspace to area of land. As a rule of thumb, FARs of 1.5 or less are well suited to automobiles, those of six and above are well suited to trains. The range of densities from about two up to about four is not well served by conventional public or private transport. Many cities have grown into these densities, and are suffering traffic problems. Personal rapid transit could provide a solution to this problem. Land uses support activities. Those activities are spatially separated. People need transport to go from one to the other (from home to work to shop back to home for instance). Transport is a "derived demand," in that transport is unnecessary but for the activities pursued at the ends of trips. Good land use keeps common activities close (e.g. housing and food shopping), and places higher-density development closer to transportation lines and hubs. Poor land use concentrates activities (such as jobs) far from other destinations (such as housing and shopping). There are economies of agglomeration. Beyond transportation some land uses are more efficient when clustered. Transportation facilities consume land, and in cities, pavement (devoted to streets and parking) can easily exceed 20 percent of the total land use. An efficient transport system can reduce land waste.

Transport, energy, and the environment

Transport is a major use of energy, and transport burns most of the world's petroleum. Hydrocarbon fuels produce carbon dioxide, a greenhouse gas widely thought to be the chief cause of global climate change, and petroleum-powered engines, especially inefficient ones, create air pollution, including nitrous oxides and particulates (soot). Although vehicles in the United States have been getting cleaner because of environmental regulations, this has been offset by an increase in the number of vehicles and more use of each vehicle. Other environmental impacts of transport systems include traffic congestion, toxic runoff from roads and parking lots that can pollute water supplies and aquatic ecosystems, and automobile-oriented urban sprawl, which can consume natural habitat and agricultural lands. Low-pollution fuels can reduce pollution. Low pollution fuels may have a reduced carbon content, and thereby contribute less in the way of carbon dioxide emissions, and generally have reduced sulfur, since sulfur exhaust is a cause of acid rain. The most popular low-pollution fuel at this time is liquified natural gas. Hydrogen is an even lower-pollution fuel that produces no carbon dioxide, but producing and storing it economically is currently not feasible. Other alternative renewable energy sources such as biodiesel are being researched heavily. Another strategy is to make vehicles more efficient, which reduces pollution and waste by reducing the energy use. Electric vehicles use efficient electric motors, but their range is limited by either the extent of the electric transmission system or by the storage capacity of batteries. Electrified public transport generally uses overhead wires or third rails to transmit electricity to vehicles, and is used for both rail and bus transport. Battery electric vehicles store their electric fuel onboard in a battery pack. Another method is to generate energy using fuel cells, which may eventually be two to five times as efficient as the internal combustion engines currently used in most vehicles. Another effective method is to streamline ground vehicles, which spend up to 75% of their energy on air-resistance, and to reduce their weight. Regenerative braking is possible in all electric vehicles and recaptures the energy normally lost to braking, and is becoming common in rail vehicles. In internal combustion automobiles and buses, regenerative braking is not possible, unless electric vehicle components are also a part of the powertrain, these are called hybrid electric vehicles. Shifting travel from automobiles to well-utilized public transport can reduce energy consumption and traffic congestion. Use of non-motorized modes walking and bicycling also reduces the consumption of fossil fuels. However, as most areas get wealthier, the use of these modes declines. There are a few wealthy cities where bicycling comprises a significant share of trips, including Copenhagen, Denmark and Groningen, Netherlands. A number of other cities, including London, Paris, New York, Bogotá, Chicago, and San Francisco, are creating networks of bicycle lanes and bicycle paths to encourage bicycling by increasing safety from traffic.

Transport Research

Transport research facilities are mainly attached to universities or are steered by the state. In most countries (not in France and Spain) one can see now how laboratories are brought into PPP-operation, where industry takes over part of the share. Some major players in Europe:
- Transport Research Laboratory [http://www.trl.co.uk/ TRL UK]
- [http://www.vtt.fi/transport/ VTT FI]
- [http://www.lcpc.fr LCPC FR]
- [http://www.inrets.fr INRETS FR]
- [http://www.certu.fr CERTU FR]
- [http://www.dlr.de/dlr/Verkehr DLR DE]
- [http://www.crf.it CRF IT]
- [http://www.vv.tno.nl TNO NL]
- [http://www.cedex.es/ CEDEX ES]
- [http://www.cemt.org/jtrc/ Joint OECD-ECMT Transport Research Centre]
- [http://www.cemt.org/index.htm European Conference of Ministers of Transport] USA:
- http://www.its.berkeley.edu Institute of Transportation Studies, University of California, Berkeley
- National Transportation Research Center
- [http://www.trb.org/ Transportation Research Board] The European Commission supports the co-operation and collaboration amongst the transport laboratories by funding projects like EXTR@Web and [http://www.intransnet.org Intransnet]. Especially the transition from planned economy to achieving a stable position on the market will be a challenge for laboratories in the new member states. Another EU-project [http://www.etra.cc etra.cc]is coping with those problems.

Narrowboat

A narrowboat is a boat or small barge used on narrow beam canals in Britain. Modern narrowboats are made about six feet ten inches (about 208 cm) wide. They are typically up to 72 feet (22 metres) long, although some locks are restricted to boats 60 feet (18 m) long and a few to only 40 feet (12 m).

History

Narrowboats are descendants of the working boats used during the Industrial Revolution. The first boats were wooden, horse-drawn, and designed for cargo rather than passengers. The canals went into economic decline in the 1830s as the new railways took away their business, and the impoverished boat-operators began to live on their boats as a way of saving money. Large families of 'boat people' were squeezed into tiny cabins, which were often ornately painted with traditional designs, usually of roses and castles. There are many enthusiasts dedicated to restoring these old boats, and new 'narrowboats' are built to similar designs. The original boats are sometimes called narrow boats to distinguish them from the modern narrowboats.

Modern narrowboats

Modern narrowboats have steel bodies and diesel engines, and are used as homes and for recreation. Some boats are replicas of the old working boats, complete with traditional paintwork. The number of licensed boats on British Waterways is estimated at about 48,000 (British Waterways, 2004), of which most are narrowboats. There are perhaps another 5,000 legitimately unlicensed boats kept in private moorings or on other waterways.

National organisations

- National Association of Boat Owners (NABO) - 3,000 members in 2004

Ship

vessel Amerigo Vespucci in New York Harbor, 1976]] A ship is a large, sea-going watercraft, sometimes with multiple decks. A ship usually has sufficient size to carry its own boats, such as lifeboats, dinghies, or runabouts. A rule of thumb saying (though it doesn't always apply) goes: "a boat can fit on a ship, but a ship can't fit on a boat". Often local law and regulation will define the exact size (or the number of masts) which a boat requires to become a ship. (Note that one refers to submarines as "boats"). Compare vessel. During the age of sail, ship signified a ship-rigged vessel, that is, one with three or more masts, usually three, all square-rigged. Such a vessel would normally have one fore and aft sail on her aftermost mast which was usually the mizzen. Almost invariably she would also have a bowsprit but this was not part of the definition. The same economic pressures which increased sizes to the point of carrying four or five masts, also introduced the fore and aft rig to larger vessels, so few ship-rigged vessels were built with more than three masts. The five-masted Preussen was the outstanding example but the big German ships and barques were built partly for prestige reasons. Nautical means related to sailors, particularly customs and practices at sea. Naval is the adjective pertaining to ships though in common usage, it has come to be more particularly associated with the noun 'navy'.

Measuring ships

One can measure ships in terms of overall length, length of the waterline, beam (breadth), depth (distance between the crown of the weather deck and the top of the keelson), draft (distance between the highest waterline and the bottom of the ship) and tonnage. A number of different tonnage definitions exist; most measure volume rather than weight and are used when describing merchant ships.
- Gross tonnage is a measure of the total internal volume of the ship.
- Net tonnage is expresses a merchant vessel's earning capacity and gives the internal capacity of that part of the ship available for cargo or passengers.
- Thames measurement tonnage was used for smaller vessels and worked to a formula: (length - beam) x beam x ½beam / 94
- Displacement tonnage is normally applied to warships and equals the actual weight of a ship complete with crew, fuel, stores and water.
- Light ship tonnage measures the actual weight of the ship with no fuel, no persons, no cargo, no water on board is not usually quoted.
- Deadweight tonnage is the weight of cargo, stores, passengers etc. which when added to the weight of the ship's structure and equipment, will bring the vessel down to her designed waterline. The word "displacement" arises from the basic physical law, discovered by Archimedes, that the weight of a floating object equates exactly to that of the water which would otherwise occupy the "hole in the water" displaced by the ship. In Britain until the Merchant Shipping Act of 1876, ship-owners could load their vessels until their decks were almost awash, resulting in a dangerously unstable condition. Additionally, anyone who signed onto such a ship for a voyage and, upon realizing the danger, chose to leave the ship, could end up in jail. Samuel Plimsoll, a member of Parliament, realised the problem and engaged some engineers to derive a fairly simple formula to determine the position of a line on the side of any specific ship's hull which, when it reached the surface of the water during loading of cargo, meant the ship had reached its maximum safe loading level. To this day, that mark, called the "Plimsoll Mark", exists on ships' sides, and consists of a circle with a horizontal line through the center. Because different types of water, (summer, fresh, tropical fresh, winter north Atlantic) have different densities, subsequent regulations required painting a group of lines forward of the Plimsoll mark to indicate the safe depth (or freeboard above the surface) to which a specific ship could load in water of various densities. Hence the "ladder" of lines seen forward of the Plimsoll mark to this day.

Propulsion

Until the application of the steam engine to ships in the early 19th century, oars propelled galleys or the wind propelled sailing ships. Before mechanisation, merchant ships always used sail, but as long as naval warfare depended on ships closing to ram or to fight hand-to-hand, galleys dominated in marine conflicts because of their maneuverability and speed. The Greek navies that fought in the Peloponnesian War used triremes, as did the Romans contesting the Battle of Actium. The use of large numbers of cannon from the 16th century meant that maneuverability took second place to broadside weight; this led to the dominance of the sail-powered warship. The development of the steamship became a complex process, the first commercial success accruing to Robert Fulton's North River Steamboat (often called Clermont) in the USA in 1807, followed in Europe by the 45-foot PS Comet of 1812. Steam propulsion progressed considerably over the rest of the 19th century. Notable developments included the condenser, which reduced the requirement for fresh water, and the multiple expansion engine, which improved efficiency. As the means of transmitting the engine's power, the paddle wheel gave way to the more efficient screw propeller. The marine steam turbine developed by Sir Charles Algernon Parsons, brought the power to weight ratio down. He had achieved publicity by demonstrating it unofficially in the 100-foot Turbinia at the Spithead Naval Review in 1897. This facilitated a generation of high-speed liners in the first half of the 20th century and rendered the reciprocating steam engine out of date, in warships. The marine diesel engine first came into use around 1912: either the Vulcanus or the Selandia (depending upon who you talk to) first deployed it. It soon offered even greater efficiency than the steam turbine but for many years had an inferior power-to-space ratio. About this period too, heavy fuel oil came into more general use and began to replace coal as the fuel of choice in steamships. Its great advantages were the convenience and the reduction in manning owing to the removal of the need for trimmers and of stokers in the old-fashioned numbers. Most ships built since around 1960 have used diesel power or motors; one exception, Queen Elizabeth 2 of 1968, started with steam turbines but subsequently converted to diesel as a cost-saving measure. A few ships have used nuclear reactors, but this is not a separate form of propulsion. It merely makes steam to drive the turbines. Nonetheless, it has caused concerns about safety and waste disposal. It has become usual only in large aircraft carriers and in submarines, where the ability to run submerged for long periods holds obvious advantage. In such long-endurance vessels, the saving in bunkerage too, is an important consideration.

General terminology

Ships may occur collectively as fleets, flotillas or squadrons. Convoys of ships commonly occur. A collection of ships for military purposes may compose a navy or a task force. In the past, people counting or grouping disparate types of ship may refer to the individual vessels as bottoms. Groups of sailing ships could constitute, say, a fleet of 40 sail. Groups of submarines (particularly German U-boats in the 1940s) may hunt in packs (often erroneously called wolf packs).

Shipboard terminology

See also: Glossary of nautical terms. The complexity of ships, particularly of sailing ships, led to the development of a rich and various vocabulary. Many of the following terms link to more detailed discussions of nautical terminology.
- Amidships - toward the middle of the vessel.
- Bow - strictly, one of the two curved structures where the hull broadens out from the stem (the pointed end). The bows is a term for the head of the vessel or front of the ship. Compare prow, a more poetical term for the ship's head.
- Stern - the after end of the ship.
- Aft - towards the stern when the relationship is within the ship.
- Astern beyond the stern where the relationship is outside the vessel.
- Starboard - the side of the ship which lies to the right when an observer within the ship faces forward.
- Port - the side of the ship which lies to the left when an observer within the ship faces forward. (A mnemonic to distinguish port and starboard notes that left and port both have four letters. Another incorporates the navigation light: Is there any red port left?)
- (Navigation) Bridge - A structure above the weather deck, extending the full width of the vessel, which houses a command centre, itself called by association, the bridge. A bridge usually extends a little beyond the ship's side to enable observation of boats alongside, or the proximity of a dock or lock gate; these projections are called bridge wings. In big vessels, a docking bridge used to be found aft. (See Lord, Walter. A Night to Remember (1976) p.96). It enabled an officer to observe docking manoeuvres before giving orders. RMS Titanic had one but they have been superseded by closed circuit television cameras.
- Bulkheads - internal "walls" in a ship. Bulkheads are the vertical equivalent of decks. They have a structural function as well as dividing spaces. They serve to prevent collapse of the hull under stress, to maintain stability, in the event of flooding, and to contain fire. Many bulkheads feature watertight doors which, in the case of certain types of ships, the crew may close remotely. An internal "wall" that is not load-bearing is usually referred to as a "partition". It is to a bulkhead as a flat is to a deck.
- Cabin - an enclosed room on a deck or flat.
- Capstan - a winch with a vertical axis.
- Coaming - Raised edges of hatches in decks for keeping water and articles free on the deck from falling into the hold.
- Decks - the structures forming the approximately horizontal surfaces in the ship's general structure. Unlike flats, they are a structural part of the ship.
- Deck Head - The under-side of the deck above. Sometimes panelled over to hide the pipe work. This panelling, like that lining the bottom and sides of the holds, is the ceiling.
- Draft - The vertical distance from the current waterline to the lowest point of the ship or in the part of the ship under consideration.
- Figurehead - symbolic image at the head of a traditional sailing ship or early steamer.
- Forecastle - a partial deck, above the upper deck and at the head of the vessel; traditionally the sailors' living quarters.
- Freeboard - The vertical distance from the current waterline to the highest continuous watertight deck. This usually varies from one part to another.
- Galley - the kitchen of the ship
- Gunwale - Formerly a fabricated band placed for strengthening around the ship at the main or upper deck level to accommodate the stresses imposed by the use of artillery. In later use it is the angle between the ship’s side and upper deck. It remained as a structural member, in wooden boats where it was mounted inboard of the sheer strake regardless of the need for gunnery.
- Bulwark - the extension of the ship's side above the level of the weather deck.
- Hold - In earlier use, below the orlop deck, the lower part of the interior of a ship's hull, especially when considered as storage space, as for cargo. In later merchant vessels it extended up through the decks to the underside of the weather deck.
- Hull - the shell and framework of the basic flotation-oriented part of a ship
- Keel - the central structural basis of the hull
- Kelson - the timber immediately above the keel of a wooden ship.
- Mast - a spar (in a ship, a very heavy one stepped in the keelson) formerly designed for the support of one or more sails. In modern ships, it is a steel or aluminium fabrication which carries navigation lights, radar antennae etc.
- Prow - a poetical alternative term for bows.
- Scupper - a drainage waterway at the edge of a deck, is drained by a pipe or, on the weather deck, a small opening in the bulwarks, leading overboard. It is called a scupper which is distinct from larger openings with hinged covers on the bulwarks, designed for relieving the ship of large quantities of water in a seaway. These are called freeing ports or wash ports..
- Windlass - A winch mechanism, usually with a horizontal axis. used where mechanical advantage greater than that obtainable by block and tackle was needed.
- Weather deck - whichever deck is that exposed to the weather – usually either the main deck or, in larger vessels, the upper deck.

Some types of ships and boats

- Aircraft carrier
- Auto carrier
- Bulk carrier
- Cable Layer
- Capital ship
- Cargo ship
- Catamaran
- Coaster
- Commerce raider
- Container ship
- Corvette
- Cruise ship
- Cruiser
- Cutter
- Destroyer
- Diving support vessel
- Ferry
- Frigate
- Guided missile cruiser
- Icebreaker
- Junk
- Laker
- Lugger
- Minesweeper
- Minehunter
- Ocean liner
- Panamax
- Reefer (refrigerated ship)
- Research vessel
- RO-RO ship (roll on, roll off)
- Sailing ship
- Sloop
- Submarine
- Supertanker
- Tanker
- Tender
- Train ferry
- Tugboat
- Shipyard
- Yacht

Some historical types of ships and boats

Yacht
- Barque A sailing vessel with three or more masts, fore-and-aft rigged on only the aftermost.
- Barquentine A sailing vessel with three or more masts, square-rigged only on the foremast.
- Battle cruiser A light battleship.
- Battleship a large, heavily-armoured and heavily-gunned warship. A term which generally post-dates sailing warships.
- Bilander
- Bireme An ancient vessel, propelled by two banks of oars.
- Birlinn
- Blockade runner A ship whose current business is to slip past a blockade.
- Brig A two-masted, square-rigged vessel.
- Brigantine A two-masted vessel, square-rigged on the foremast and fore-and-aft rigged on the main.
- Caravel
- Carrack
- Clipper
- Cog
- Collier A vessel designed for the coal trade.
- Dreadnought An early twentieth century class of battleship.
- Dromons are the precursors to galleys.
- East Indiaman An armed merchantman belonging to one of the East India companies (Dutch, British etc.)
- Fire ship A vessel of any sort, set on fire and sent into an anchorage with the aim of causing consternation and destruction. The idea is generally that of forcing an enemy fleet to put to sea in a confused, therefore vulnerable state.
- Galleass A sailing and rowing warship, equally well suited to sailing and rowing.
- Galleon A sixteenth century sailing warship.
- Galley A warship propelled by oars with a sail for use in a favourable wind.
- Galliot
- Ironclad A wooden warship with external iron plating.
- Knarr A type of Viking trade ship
- Liberty ship An American merchant ship of the late Second World War period, designed for rapid building in large numbers. (The earliest class of welded ships.)
- Longship A Viking raiding ship
- Man of war A sailing warship.
- Monitor A small, very heavily gunned warship with shallow draft. Designed for land bombardment.
- Paddle steamer A steam-propelled, paddle-driven vessel, a name commonly applied to nineteenth century excursion steamers.
- Pantserschip A Dutch ironclad. By the end of the nineteenth century, the name was applied to a heavy gunboat designed for colonial service.
- Penteconter An ancient warship propelled by 50 oars, 25 on each side.
- Pram A small dinghy, originally of a clinker construction and called in English, as in Danish, a praam. The Danish orthography has changed so that it would now be a pråm in its original language. It has a transom at both ends, the forward one usually small and steeply raked in the traditional design.
- Q-ship A commerce raider camouflaged as a merchant vessel.
- Quinquereme An ancient warship propelled by three banks of oars. On the upper row three rowers hold one oar, on the middle row - two rowers, and on the lower row - one man to an oar.
- Schooner A fore and aft-rigged vessel with two or more masts of which the foremast is shorter than the main.
- Shallop A large, heavily built, sixteenth century boat. Fore and aft rigged. More recently it has been a poetically frail open boat.
- Small Waterplane Area Twin Hull (SWATH) A modern ship design used for Research Vessels and other purposes needing a steady ship in rough seas.
- Steamship A ship propelled by a steam engine.
- Ship of the line A sailing warship of first, second or third rate. That is, with 64 or more guns. Before the late eighteenth century, fourth rates (50-60 guns) also served in the line of battle.
- Torpedo boat A small, fast surface vessel designed for launching torpedoes.
- Tramp steamer A steamer which takes on cargo when and where it can find it.
- Trireme An ancient warship propelled by three banks of oars.
- Xebec
- Victory ship

Quotations

:I must go down to the sea again, to the lonely sea and the sky, :And all I ask is a tall ship, and a star to steer her by... :-John Masefield

External links

- [http://www.shipsystems.net.tf - Reference page]
- [http://www.shipspotting.com/ ShipSpotting.com - shipping image archive]
- Category:Water transport Category:Transportation ja:船舶 ms:Kapal

Mesopotamia

, ca. 24th century BC]] Mesopotamia (Greek: Μεσοποταμία, translated from Old Persian Miyanrudan "between rivers"; Aramaic name being Beth-Nahrain "House of Two Rivers") is a region of Southwest Asia. Strictly speaking, it is the alluvial plain lying between the Tigris and Euphrates rivers, composing parts of Iraq, Turkey and Syria. More commonly, the term includes these river plains in totality as well as the surrounding lowland territories bounded by the Syrian Desert to the west, the Arabian Desert to the south, the Persian Gulf to the southeast, the Zagros Mountains to the east and the Caucasus mountains to the north. Mesopotamia is famous for the site of some of the oldest civilizations in the world. Writings from Mesopotamia (Uruk, modern Warka) are among the earliest known in the world, giving Mesopotamia a reputation of being the "Cradle of Civilization". The age of Sumerian writing is about on a par with Egyptian hieroglyphs, and some yet older inscriptions are known, probably ranking as proto-writing (Old European script, Naqada [http://www.touregypt.net/ebph5.htm].

City states and Imperial glory

Mesopotamia was settled, and conquered, by numerous ancient civilizations:
- Mesopotamia was home to some of the oldest major ancient civilizations, including the Sumerians, Akkadians, Babylonians and Assyrians.
- In 5000 BC, the Sumerians arrived in Mesopotamia. The Semites arrived in 2900 BC and by 2000 BC they had mixed peacefully with the Sumerians and had assumed political dominance.
- The Mitanni were an eastern Indo-European people (belonging to the linguistic "satem" group) who settled in northern Mesopotamia circa 1600 BC South-East of Turkey and by circa 1450 BC established a medium-size empire east, north and west, and temporarily made tributary vassals out of kings in the west, even as far as Kafti (minoic Crete) and making them a major threat for the Pharaoh.
- By 1300 BC they had been reduced to their homeland and the status of vassal of the Hatti (the Hittites), a western Indo-European people (belonging to the linguistic "kentum" group) who dominated most of Asia Minor from their capital of Hattutshash (modern Turkey) and threatened Egypt even more.
- Meanwhile the Kassites established a strong realm, Sangar, in southern Mesopotamia, with Babel as its capital, not touched by Mitanni or Hittites. But the Elamites threatened or invaded them.
- Chaldaean New Babylonia circa 600 BC.

Later history

Elamites
- The region ceased to be a major power house since its inclusion in the Persian Empire of the Achaemenids, apparently as two satrapies, Babylonia in the south and Athura (from Assyria) in the north.
- After the conquest of all Persia by the Hellenizing Macedonian king Alexander the Great, the satrapies were part of the major diadochy, the Seleucid Empire, almost until its elimination by Greater Armenia in 83 BC.
- Most of Mesopotamia then became part of the Parthian Empire of the Arsakides. However part, in the northwest, became Roman. Under the Tetrarchy, this was divided into two provinces, called Osrhoene (around Edessa; roughly the modern-day border between Turkey and Syria) and Mesopotamia (a bit more northeast).
- During the time of the Persian Empire of Sassanids, their much larger share of Mesopotamia was called Dil-i Iranshahr meaning "Iran's Heart" and the metropol Ctesiphon (facing ancient Seleukia across the Tigris), the capital of Persia, was situated in Mesopotamia.
- Since the early caliphs annexed all Persia and advanced even further, Mesopotamia was reunited, but governed as two provinces: northern Mesopotamia (with Mosul) and southern Iraq (with Baghdad, the later caliphal capital). Add education

List of links

Baghdad These civilizations arose from earlier settlements and cultures which were among the first to make use of agriculture.
- Neolithic settlements e.g., Jarmo, Tell Abu Hureyra
- Hassuna period
- Halaf period (or Halafian)
- Samarra period (or Samarran), e.g., Choga Mami
- Ubaid period, e.g., Eridu
- Uruk period, named after the city Uruk.
- Sumerian Early Dynastic period Early cities in this region include:
- lower Mesopotamia / Sumer
- Uruk
- Isin
- Lagash
- Akkad
- Agade
- Babylon
- Kish
- Nippur
- upper Mesopotamia / Assyria
- Assur
- Nineveh
- Mari
- Aleppo

Right-of-way

The phrase Right-of-way is used in two main ways: 1. with reference to the question of which of two or more moving vehicles has priority:
- for right of way among boats and ships on the water, refer to International Regulations for Preventing Collisions at Sea.
- similar rules apply on land to determine priority at a crossing or in traffic. A vehicle must yield either to pedestrians or to other vehicles that have priority. It is not an absolute right as it must be exercised in a reasonable manner with respect for the due care for one's self and for the care of others involved. See also priority signs, yield sign, stop sign.
- the term is used by analogy in the rules of fencing, requiring a fencer to parry an opponent's attack before making a riposte. It gives priority to the person making the first attack. 2. with reference to the legal status of land used in transit:
- the property along the sides of, and including, railroad tracks. Most railroad rights-of-way within the US are called an "exclusive right-of-way". Persons entering the trackway are either Qualified Roadway Workers or trespassers.
- the legal right of a government, public utility, or private business to build and maintain a transport route, pipeline, or electrical line (usually granted with government authorization or expropriation); also the land through which such construction passes;
- the legal right (usually termed an easement in common law jurisdictions) allowing a particular person, the owners or licensees of adjacent land or the general public to walk, cross, and/or drive across certain parcel of land. Usually to gain access to another parcel of land that may be enclosed or may not have easy access to a roadway; see also trespass.
- In the United Kingdom, a public right of way exists under common law if it has been used for 20 years. After hundreds of years of history, an enormous network of rights of way across private land exists with definitive maps maintained by local authorities. Apart from public roads, public rights of way in the UK can be classified as:
- footpaths,
- bridlepaths,
- roads used as public paths (RUPP) or
- Byways . category:disambiguation Category:Traffic law Category:Real property law Category:Rights of way

Polder

]] A polder is a low-lying tract of land that forms an artificial hydrological entity, enclosed by embankments known as dikes. Some need drainage by pumps to prevent the water table within it from rising too high. Some can be drained by opening sluices at low tide. The best-known examples are those polders that constitute areas of land reclaimed from a body of water, such as a lake or the sea, and are consequently below the surrounding water level. Polders are most commonly found, though not exclusively so, in the

Canal

Miscellaneous

Famous canals and lists

See also

Lake

Origin of natural lakes

Characteristics

Types of lakes

Artificial lakes

Abiotic and biotic limnology

How lakes disappear

Extraterrestrial lakes

Notable lakes

See also

External links

Ocean

Origins

Exploration

Climate

Ecology

Economy

Ancient oceans

Ocean rowing

Extraterrestrial oceans

Oceans in film

See also

External links

Irrigation

Overview

Types of irrigation

Flood (furrow) irrigation

Terracing

Overhead (sprinkler) irrigation

Center pivot irrigation

Lateral move (Side roll, Wheel line) irrigation

Drip, or trickle irrigation

Subirrigation

How an irrigation system works

History of irrigation

Problems in irrigation

See also

References

External links

Transport

Aspects of transport

Modes of transport

Categories of transport

Transport and communications

Transport and land use

Transport, energy, and the environment

Transport Research

See also

Narrowboat

History

Modern narrowboats

National organisations

See Also

Ship

Measuring ships

Propulsion

General terminology

Shipboard terminology

Some types of ships and boats

Some historical types of ships and boats

See also

Quotations

External links

Mesopotamia

City states and Imperial glory

Later history

List of links

Further reading

Right-of-way

Polder