Challenges for determining frequency of high flow spells for varying thresholds in environmental flows programmes

Abstract

High flow spells (or “pulses”) are important flow components providing ecological triggers and connectivity in rivers. While the ecological importance of flow spells is well-recognized, the link between ecosystem processes and statistical methods used to define flow spells occurrence has received little attention. Commonly, a spell is defined as an event that exceeds a threshold for a minimum number of consecutive days; however, such arbitrary metrics may be ecologically irrelevant. For example, the ecological value of a sustained high flow spell may be unaffected by a brief period in which flows fall just below the nominated threshold. The inclusion of an independence criterion has the pote..