Print PageThis paper will present the first attempt in Australia to explore the scientific and practical implications of using the framework ELOHA (Ecological Limits of Hydrologic Alteration) as a means to understand how flow regime change brought about by dams (and other infrastructure) can affect rivers and their riparian and aquatic biota at a regional scale, and to interpret findings in terms of water management. It will describe how flow regimes in streams and rivers of south-east Queensland were classified on the basis of numerous ecologically relevant hydrologic metrics ranging across magnitude, timing, duration and frequency of low and high flow events, constancy and predictability of flow, floods of various return intervals and low flow spells. The study design will be described, and a gradient of flow alteration will be demonstrated for this study region.
Results/Conclusions
From the field studies undertaken, attempts are being made to identify multivariate patterns of difference and test numerous univariate indicators of response to flow regime alterations across flow regime classes. Thresholds (if there are any), linear and other relationships of ecological response to flow regime alteration will be presented, with emphasis on responses of riparian vegetation, aquatic vegetation, and fish. Across this region there are marked climatic and stream flow variations upon which the effects of individual dams are superimposed. Separating out the impacts of flow regime change by dams is proving a challenge, and several approaches will be discussed in this presentation. The presentation will outline the strengths and constraints of the ELOHA framework, and its capacity to inform setting of environmental flow rules based on field measurements across gradients of flow regulation by dams. Several lessons already emerge from the analyses completed to date. One is that the type and degree of flow alteration can influence ecological responses of different taxa and that these effects differ among flow regime classes, as predicted in the ELOHA framework. Another is that the time since dams were built can influence the ecological response to flow regulation, such that species and assemblages may be advancing along a trajectory of response to flow alteration but not have achieved a full adjustment. Finally, thoughts about the ecological response indicators we have studied (assemblage, population, and trait indicators) will be summarised to stimulate discussion about the likely uptake of an ELOHA approach elsewhere, especially in regions with limited knowledge of aquatic systems.
