Artificial drainage systems

Depending on the groundwater table and the level of the open water in which the 

The design process of an artificial field drainage system of a reclamation area may 

Special features are wadi s. A wadi is a river valley present in dry areas that is dehydrated throughout most of the year. However, during wet periods and heavy rainfall water flows through the wadi. This may happen unexpectedly and these events are called flash floods . 

Note that land reclamations are often constructed along existing shores and banks and they may therefore block existing outlets/outfalls of systems draining the hinterland. 

An artificial field drainage system is generally designed to improve the infiltration capacity and/or to control the surface runoff. 

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If the natural drainage capacity is not sufficient to cope with the water supply by precipitation, overtopping, etc., an artificial drainage system may have to be designed. 

Should the anticipated amount of ponding and/or (uncontrolled) surface runoff be considered unacceptable, then an artificial drainage system may be necessary. This usually comprises a number of special measures that can be taken to improve the infiltration and/or to control the ponding and surface runoff in order to transport the water to a suitable location where it can be discharged into open water (river, sea) without affecting surrounding facilities. 

The capacity (dimensions, slopes, spacing of drains, gutters, ditches, etc.) of the artificial drainage system must be sufficient to remove the water from the surface without causing flooding and erosion. The open drains themselves may also have to be lined or protected against erosion by water flow. 

The design of an artificial drainage system must take into account the lay-out of the future development of the reclamation area locations of retention basins, ditches, drains and so on should not interfere with future structures. Further reference is made to Chow et al (1988). 

Drainage tests and initial measurements should not be made before 28 days have elapsed after the anodes are embedded in the artificial concrete system in order to allow the hydration of the concrete and to ensure moisture equilibrium, which can affect the potentials. The protection current density is limited to 20 mA ra"-(at the steel surface) to avoid possible reduction in the steel-concrete bond. Usual current densities lie in the range 1 to 15 mA 129-33]. 

Information on authorized and accidental releases of Tc to terrestrial ecosystems or to freshwater drainage systems from large reprocessing facilities in the former USSR, e.g., Chelyabinsk (Ma-yak PA), Krasnoyarsk (KMCIC), or Tomsk (SCC) is not available. However, significant amovmt of Tc have been identified in ground water and artificial reservoirs associated with Techa River in the close vicinity of the Mayak PA. 

Secure Landfills Secure landfills for hazardous waste must meet stringent standards of the EPA. A secure landfill must have an impervious clay base or an artificial liner. These features intend to contain any leachate. A drainage system around the landfill collects groundwater and prevents it from entering the landfill. Special designs and instrumentation monitor the drainage system and groundwater near and under the landfill for leachate. 

Relevant bodies of water are aU streams, rivers, artificial or natural lakes, ravines, marshes, drainage systems and sewerage systems that may produce or affect flooding on or adjacent to the nuclear power plant site. Bodies of water that are outside the watershed in which the plant is located, but that may, by overflowing the watershed divide, produce or affect flooding of the plant site, are also considered relevant bodies of water. 

Mine Drainage. In recent years it has become clear that the environmental impact of acid mine drainage can be minimized by the construction of artificial wetlands that combine geochemistry and biological treatments. These systems are being designed for a range of wastewaters, most of which fall outside the scope of this article. 

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