Derivation of low flow distribution functions using recession curves

Abstract

Recession analysis and low flow frequency analysis have been treated by tradition as separate problems, although both are related to low flow conditions. The shape and analytical expression of the streamflow decay during rainless periods might give an insight into the behaviour of the tails of low flow distribution functions. Furthermore, models for streamflow recession have, as a rule, a more or less straightforward physical background and this might be of help in the interpretation and regionalization of parameters of low flow distribution functions. The present paper is an attempt to combine results from these two separate fields in order to use recession equations to derive theoretical expressions for low flow distribution functions. The derived distribution approach together with the concept of compound distributions are used to deduce expressions for a family of low flow distributions related to linear and non-linear recession models. Approaches for parameter estimation are elaborated and exemplified on low flow data from the Nordic countries.