Duration line

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A duration curve is the graphical representation of statistically equivalent individual observations (measured values) in the order of their size. With the help of duration lines, the frequency of falling below or exceeding the measured values ​​in a certain period of time is described. A duration curve is created by sorting the measured values ​​according to their size, usually starting with the smallest value, with the abscissa representing the time axis.

Example of a duration curve with the associated hydrograph

application

  • Duration curves are in the hydrography and hydrology required wherever water levels and outflows for a service life, for example, to design of turbines in hydroelectric plants are decisive. Duration lines show how many days of a year ( discharge year or calendar year), individual discharges , river water or groundwater levels were undershot. This section of the abscissa is also referred to as the days below the limit. The respective measured values ​​are created from the runoff and water level measurements at gauges and groundwater observation pipes . Duration curves can also be determined from the mean values ​​of long-term discharge measurements. These show the frequency below and thus above the frequency of discharges as a long-term mean.
  • In inland navigation , the duration curve is used to determine the days below the minimum fairway depth due to the lack of water in the river bed.
  • In the transport sector, continuous lines of traffic volume are used to dimension transport facilities. Typed duration lines of traffic on motorways can be found, for example, in the recommendations for economic studies of roads .

See also

literature

  • G. Steierwald, HD Künne, W. Vogt (Ed.): City traffic planning. Basics, methods, goals. 2., rework. and exp. Edition. Springer, Berlin 2005.

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