Research and analysis

Low flow frequency analysis guidelines for best practice

Provides guidance on best practice for frequency analysis of annual minimum flows.



The general issues to be considered when contemplating a frequency analysis are discussed with a strong emphasis on likely sources of error and uncertainty. In order to encourage a consistent methodology to be adopted in the UK a single parametric approach for estimating the probability of occurrence of low flow events is recommended. This approach is based on the use of L-moments with a Pearson Type III probability distribution to estimate the flow - return period relationship for annual minima of different durations.