Relationships between low-flow characteristics of South African streams

Abstract

The low-flow regime of a river may be described in terms of various characteristics (indices). These characteristics may have multiple use in different areas of water-related research and practice and uncertainty often exists as to which low-flow characteristic is the most suitable for a specific purpose. The paper illustrates that many low-flow characteristics exhibit a strong intercorrelation and therefore one low-flow index may often be derived from another by means of regression relationships. Consequently, only one “primary” low-flow index may need to be initially estimated (either from available time series or by regionalisation techniques). The study examines various types of low-flow indices which have been estimated from more then 200 gauged daily streamflow records in South Africa. Several indices extracted from one day long-term annual flow duration curves have been used as primary characteristics. The relationships between low-flow characteristics are illustrated on the scale of the entire country and on the scale of two smaller drainage regions.

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