Author(s): Konstantin Ochs; Rui Rivaes; Teresa Ferreira; Gregory Egger

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Abstract: In regulated Mediterranean rivers from intensive agricultural watersheds the outgrowth of aquatic vegetation notably by invasive species is a common phenomenon [1]. Although the high sensitivity of aquatic vegetation to instream hydraulic conditions is well known [2], [3], management approaches based on ecosystem’ regulative functions are still poorly explored. The aim of our study was therefore to apply physical habitat simulation techniques promoted by the Instream Flow Incremental Method (IFIM) [4] for the first time on aquatic macrophytes. We wanted to model the shifts in habitat suitability under different flow scenarios in the Sorraia river in central Portugal and test whether through the setting of minimum annual flows the risk of invasion and channel encroachment by nuisance species can be controlled. Our hypothesis is that intensified summer low flows through water abstraction for irrigation create physical instream conditions that favor the excessive growth of Myriophyllum aquaticum and that this situation can be mitigated through the establishment of minimum flows above a certain threshold.

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Year: 2018