Flow variability and the ecology of large rivers

TLDR

Ecological processes in large rivers are governed by flow variability, yet suitable measures that capture group‑level patterns and link to ecology are lacking. This paper identifies 11 independent hydrological variability metrics to categorize river types and link them to fish biology, and proposes extensions to the Flood Pulse Concept to account for climatic differences. Using multivariate analyses of hydrographs from 52 worldwide rivers, the authors derived 11 independent variability metrics and examined their relationships with climate and fish biology. The analysis revealed distinct river groups aligned with tropical and dryland climates, but continental rivers span extremes, highlighting limitations of simple classification and underscoring the importance of hydrological variability for river conservation and management.

Abstract

Ecological processes in large rivers are controlled by their flow variability. However, it is difficult to find measures of hydrological variability that characterize groups of rivers and can also be used to generate hypotheses about their ecology. Multivariate analyses of the hydrographs of 52 rivers worldwide revealed distinctive patterns of flow variability that were often correlated with climate. For example, there were groups of rivers that corresponded broadly with ‘tropical’ and ‘dryland’ climates. However, some rivers from continental climates occupy both extremes of this range, illustrating the limitations of simple classification. Individual rivers and groups of rivers may also have different hydrographic ‘signatures’, and attempts to combine measures of hydrological variability into indices mask biologically significant information. This paper identifies 11 relatively independent measures of hydrological variability that help categorize river types and are each associated with aspects of fish biology. Ways are suggested by which the Flood Pulse Concept can be expanded to encompass hydrological variability and accommodate differences among groups of rivers from different climatic regions. Such recognition of the complex role of hydrological variability enhances the value of the concept for river conservation, management and restoration.