Abstract
Abstract. Environmental flows remain biased toward the traditional biological group of fish species. Consequently, these flows ignore the inter-annual flow variability that rules species with longer lifecycles and therefore disregard the long-term perspective of the riverine ecosystem. We analyzed the importance of considering riparian requirements for the long-term efficiency of environmental flows. For that analysis, we modeled the riparian vegetation development for a decade facing different environmental flows in two case studies. Next, we assessed the corresponding fish habitat availability of three common fish species in each of the resulting riparian landscape scenarios. Modeling results demonstrated that the environmental flows disregarding riparian vegetation requirements promoted riparian degradation, particularly vegetation encroachment. Such circumstance altered the hydraulic characteristics of the river channel where flow depths and velocities underwent local changes of up to 10 cm and 40 cm s−1, respectively. Accordingly, after a decade of this flow regime, the available habitat area for the considered fish species experienced modifications of up to 110 % when compared to the natural habitat. In turn, environmental flows regarding riparian vegetation requirements were able to maintain riparian vegetation near natural standards, thereby preserving the hydraulic characteristics of the river channel and sustaining the fish habitat close to the natural condition. As a result, fish habitat availability never changed more than 17 % from the natural habitat.
Highlights
Freshwater ecosystems provide vital services for human existence but are on top of the world’s most threatened ecosystems (Dudgeon et al, 2006; Revenga et al, 2000), primarily due to river damming (Allan and Castillo, 2007)
Initial phase (IP) is reduced to approximately 3 % in OCBA and 6 % in OCPR, while Pioneer phase (PP) is nonexistent in both cases
Early Successional Woodland phase (ES) covers up to approximately 48 and 26 % of the corresponding study areas, whereas Established Forest phase (EF) and Mature Forest phase (MF) maintain about the same area in both case studies
Summary
Freshwater ecosystems provide vital services for human existence but are on top of the world’s most threatened ecosystems (Dudgeon et al, 2006; Revenga et al, 2000), primarily due to river damming (Allan and Castillo, 2007). The ability to provide sufficient water to ensure the functioning of freshwater ecosystems is an important concern as its capacity to provide goods and services is sustained by water-dependent ecological processes (Acreman, 2001). The relevance of this subject compelled the scientific community to appeal to all governments and water-related institutions across the globe to engage in environmental flow restoration and maintenance in every river (Brisbane Declaration, 2007). It is agreed that environmental flows must ideally be based on the ecological requirements of different biological communities
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