drainage(redirected from Subsurface drainage)
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drainage,in agriculture, the removal of excess water from the soil, either by a system of surface ditches, or by underground conduits if required by soil conditions and land contour. Diesel or centrifugal pumps are sometimes used to drain large areas. Drainage was practiced in the Nile basin c.400 B.C. and in ancient Rome. Today drain pipes of clay, concrete, or plastic, laid several feet underground, are much used in the United States, where c.110 million farm acres (44.5 million hectares) were artificially drained in 1987. Proper drainage improves soil structure; increases efficiency of phosphorus fertilizer; conserves soil nitrogen; and controls waterlogging, leaching, and salinization of soils caused by irrigationirrigation,
in agriculture, artificial watering of the land. Although used chiefly in regions with annual rainfall of less than 20 in. (51 cm), it is also used in wetter areas to grow certain crops, e.g., rice.
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drainage,in mining, removal of water seeping into shafts and other underground mine workings from the surrounding ground. Unless seeping water is removed continually, it may endanger haulage and mining equipment, weaken supporting structures, and, in some instances, flood the mine completely. Water in a mine is drained into sumps, or reservoirs, usually excavated below the lowest working level of the mine, and is then removed by pumps. Methods to minimize seepage include the sealing of visible fissures through which water enters and the injection of concrete into the ground surrounding the shafts.
the removal of ground and surface water from working shafts (in mines) and quarries and during the driving of vertical, inclined, and horizontal mines, pits, and trenches. Drainage normally involves the raising of the water, but from adits and trenches it is done by gravity flow. The various systems of shaft (mine) or quarry drainage used on open and underground mines include drainage ditches, header pipes to carry the water from the underground drainage devices (sheet and flow-through filters), subsidiary and main catchment basins, a main pump chamber, and pressure piping. In open mines, ground and surface (rain) water moves via a network of drainage ditches on the levels to the main catchment basin and is removed from the quarry by pumps. In sinking vertical and horizontal mineshafts, drainage occurs by means of hoisting vessels (buckets and skips) and face pumps when the flow is small (up to 10 cu m per hr); for flows of 10-40 cu m per hr, suspended vertical pumps are used; when the flow is heavier, one of the special techniques (plugging, freezing, drawdown, and in unstable rocks, the drop-shaft method) is used. Extensive use is made of screw-type face pumps in sinking horizontal shafts.
REFERENCERipp, M. G., A. I. Petukhov, and A. M. Miroshnik. Rudnichnye ventiliatornye i vodootlivnye ustanovki. Moscow, 1968.
V. A. BOIARSKII
the prevention or elimination of the unfavorable effects of water in human economic activity. Drainage is most important for agriculture, where the removal of excess water from the soil root zone is a type of land reclamation that makes it possible to till new lands and increase productivity. Drainage involves hydraulic engineering methods, agricultural techniques, and management measures based on hydraulic engineering methods of controlled removal of water from the soil root zone. Drainage improves soil moisture and ventilation, accelerates the thawing and drying of the soil in the spring, and promotes the development of beneficial microflora and the growth of crops. This makes it possible to increase grain crop yields on drained lands to 30–40 quintals per hectare (ha), vegetables to 600–800 quintals, potatoes to 200–300 quintals, and hay to 100–120 quintals per ha, that is, an increase of 50–200 percent over the yield on unreclaimed land. Drainage is one of the principal means of increasing the productivity of lands with excess water, and it ensures efficient use of machinery and new chemicals.
Drainage is also necessary to protect cities, towns, and industrial facilities against seepage of groundwater from reservoirs or seas, to improve forest growth, and to protect mining operations.
Drainage in agriculture was first practiced in Egypt in 3000 B.C. (the Fayyum Oasis). In 2000 B.C., clay drainage systems were used to drain arable lands in Mesopotamia, and stone drainage systems were used in the vineyards of ancient Rome. The coastal lowlands of the Netherlands have been drained since the ninth and tenth centuries. The first drainage systems using handmade ceramic pipes were built near Bosworth, England, in the 16th century. Open canals were first used for drainage in Europe in the late 18th century. In the early 19th century drain tiles were used in Europe, and by the end of the century, in the United States. Russians knew about drainage in the late 14th century, but it was not until the second half of the 19th century that it was introduced in the Poles’e, the northwestern provinces, and the Central Industrial Zone (the former Tver’, Vladimir, Riazan’, Moscow, and Yaroslavl provinces); in the 1890’s, drainage systems were built in Western Siberia (the Barabinsk and Ishim steppes).
At the beginning of the 20th century the total area of drained land in the world did not exceed 20 million hectares (ha), which included 2.5 million ha in Russia (2.8 million ha in 1913). In the 20th century the greatest amount of drainage work has been done in the United States (more than 40 million ha of large tracts had been drained by 1972), Canada, Japan, India, Poland, Great Britain, Hungary, Finland, Sweden, the Netherlands (polders), and the German Democratic Republic. By 1972 more than 100 million ha were being drained in the world, 10.9 million ha in the USSR (nonchernozem zone of the European part of the RSFSR, Byelorussia, the Baltic Region, Western Siberia). Extensive, efficient drainage work is under way in the Poles’e, the Meshchera Lowland, Colchis, the valley of the Amur River, and the Baltic Region.
Marshes as well as marshy mineralized soils that are permanently or temporarily wet are drained for agricultural use. The drainage systems (open or subsurface) have drainage networks that ensure removal of excess water to the reclamation standard (depth of groundwater that ensures that the soil root zone receives the moisture necessary for high yields). Drainage methods and equipment are determined by the source of the water and the agricultural use of the land.
If the source is atmospheric water, surface runoff is accelerated by means of open or closed (subsurface) collectors. If the source is groundwater, flow is accelerated and the level of groundwater is lowered to the reclamation standard by means of a drainage system or widely spaced deep channels. Groundwater flow is intercepted by catch channels (on the side of the drainage basin) or lateral drains (on the side of the river or reservoir). Where the source is confined groundwater, the piezometric surface of the water is lowered by vertical drainage or deep drains, and as an accompanying measure surface runoff is accelerated. If the source is water from slopes, the lands being drained are surrounded on the side bordering the slope by channels, and anti-erosion steps are taken to hold back water and reduce overland runoff. When excess water is due to floods, the area is protected by levees (embankments) on the side of the river, lake, or sea; in addition, a drainage network with sluices on the main channel is built, and pumping stations for mechanical water removal are constructed.
Agricultural reclamation measures are also initially used to drain heavy grained soils and upland swamps, primarily those whose water content is due to atmospheric precipitation. These include ridging, narrowstrip plowing, bedding, ridge planting, planting of row crops (in the Far East and Colchis), mole plowing, and other procedures that are effective only in combination with an operating drainage network.
It is usually impossible to use drained lands without soil improvement work such as cutting and removing brush and small trees; removing grassy mounds, stumps, root remains, and boulders; filling in holes and ditches; plowing and preparing drained virgin land; packing and grading the surface of peat soils; applying organic and mineral fertilizers, including lime; and growing preliminary crops to eliminate variations in soil fertility. During dry periods drained lands are irrigated (sprinkled or supplied with water through drains by sluicing the channels of the drainage network) by means of drainage-irrigation systems.
The agricultural use of drained lands is determined by geographic location, soil fertility, and the technical and management conditions of initial development. In the USSR, floodplains and low-lying marshes located near large population and industrial centers are being developed for vegetable and fodder crops. In the forest-steppe and steppe zones industrial crops such as hemp, flax, sugar beets, and potatoes are raised on drained lands. The moist subtropical Black Sea coastal area of the Caucasus is most suited for the growing of tea, citrus fruits, tung tree, laurel, and bamboo; in the Far East soybeans and rice are raised on drained land (see Table 1).
|Table 1. Use of drained lands in the USSR (thousands of hectares)|
|11ncluding 4,373,500 hectares drained by drainage systems|
|Total area of drained lands........||10,600||10,214||11,4271|
|Including land under|
|Grain crops ..............||1,441||1,423||1,708|
|Industrial crops ............||198||211||260|
|Potatoes, vegetables, and melons||227||207||245|
|Fodder crops .............||1,430||1,705||2,014|
|Hayfields and pastures .......||3,486||3,318||3,869|
In 1972 the yield on drained lands in the USSR was (in thousands of tons) 3,484.6 of grain, 38.19 of flax fiber, 2,346.7 of sugar beets (to be used for making sugar), and 2,578.5 of potatoes.
REFERENCESBrudastov, A. D. Osushenie mineral’nykh i bolotnykh pochv, 4th ed. Moscow, 1955.
Kostiakov, A. N. Osnovy melioratsii, 6th ed. Moscow, 1960.
Maslov, B. S., V. S. Stankevich, and V. Ia. Chernenok. Osushitel’nouvlazhnitel’nye sistemy. Moscow, 1973.
S. F. AVER’IANOV