Parameter Variation

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This table determines the range and distribution of each parameter chosen in the stochastic simulation. The table is divided into subsections "combined sewer system", "separate sewer system", "natural catchment" and "receiving water" according to the subsystems in the tab System.

The meaning of the columns is as follows:

•Parameter: Name of the model parameter (not editable)

•Average: Average of the model parameter (not editable), equal to the value which was entered in the subsystem on the tab System, used as value in the deterministic simulation.

•Lower limit: Lower limit of the parameter value range used in the stochastic simulation if uniform or triangular distribution is chosen. If normal or lognormal distribution is chosen the standard deviation is calculated from lower and upper limit (sigma = (upper limit - lower limit) / 4)

•Upper limit: Upper limit of the parameter value range used in the stochastic simulation if uniform or triangular distribution is chosen. If normal or lognormal distribution is chosen the standard deviation is calculated from lower and upper limit (sigma = (upper limit - lower limit) / 4)

•relative: If enabled lower and upper limit are regarded as relative values to the average value (0.8 = 0.8·average, 1.2 = 1.2·average). If disabled values are regarded as absolute values. The values are automatically recalculated if the status of the check box is changed.

•Distribution: Choice of the distribution:

•Constant (Parameter value is not varied, value always equal to average)

•Uniform (Parameter value is randomly chosen between lower and upper limit with equal probability)

•Normal (Parameter value is varied around average with a normal distribution, standard deviation sigma = (upper limit - lower limit) / 4

•Lognormal (Parameter value is varied around average with a lognormal distribution, standard deviation sigma = (upper limit - lower limit) / 4

•Triangular (Parameter is randomly chosen from a triangular distribution between lower and upper limit where the peak of the distribution is located at the value of the deterministic simulation i.e. the value in the field "Average")