Experimental methods to predict riparian vegetation responses to environmental flows in regulated rivers

This project will provide a methodology for predicting the outcome of environmental flow implementation on riparian vegetation, which is important for biodiversity and river ecosystem functions.

This project will provide a methodology for predicting the outcome of environmental flow implementation on riparian vegetation, which is important for biodiversity and river ecosystem functions.

Specifically, the researchers will forecast the outcomes of environmental flow implementation by introducing (1) flood pulses, (2) more natural water-level variation in run-of-river impoundments, and (3) bypassed reaches. These actions have been suggested as having a large potential to improve ecological conditions in regulated rivers and are potential tools to be used in the process of relicensing Swedish hydropower.

Objectives

1. Transplant vegetation to new elevations in the riparian zones by excavating turfs and move them to new
   levels, so they will experience the hydrological conditions expected following implementation of
   environmental flows. This substitutes hydrological change by spatial translocation, under the assumption that
   riparian vegetation structure is primarily controlled by inundation duration.
2. Calculate the rate and direction of vegetation response in terms of biodiversity (species richness and
   diversity) and vegetation abundance (cover and biomass) to new hydrological conditions to help forecast the
   effects of large-scale implementation of environmental flows, providing a method to help prioritize among
   ecological rehabilitation measures.
3. Predict the rate that new species are added and other species are lost in the initial responses to ecological
   restoration, so that rules for the addition and deletion of species in the assembly of restored communities can
   be formulated.
4. Provide recommendations for how to implement environmental flow options in three major types of water
   bodies in regulated river systems:
   • Reaches downstream of dams where flood pulses mimicking spring floods can be implemented: Will
   this increase plant species richness, and what is the rate of species additions and losses following
   increases in inundation duration of spring-flooded communities?
   • Run-of-river impoundments: Can their riparian zones be revegetated with the help of more natural
   seasonal variation in water levels, despite ongoing hydropeaking?
   • Bypassed reaches: Will this increase plant species richness, and what is the speed of change in species
   composition (and biodiversity) following implementation of minimum discharge with seasonal
   variation?”