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Responses of RiParian forests to hydroPeaking: towards a sustainable hydropower management

Final Report Summary - RIPEAK (Responses of RiParian forests to hydroPeaking: towards a sustainable hydropower management)

The RiPeak project (Marie Curie IEF 623691; Annex 1) has delved into the effects of the phenomenon of hydropeaking (i.e. rising or falling sub-daily discharges caused either by the turning on or off of hydro-turbines to generate electricity according to variations in the market demand) on the fluvial ecosystem, going from the changes on the fluvial hydrology and hydraulics to the resulting consequences for the riverine vegetation. Our findings are of great interest for scientists and managers, as they provide information on the ecological functioning of rivers subjected to such operating schemes thereby, providing a solid basis for the development of hydropower operation guidelines that take both ecological and economic requirements into consideration.

First (Objective 1; tasks 1 and 2), a review of the literature on hydropeaking impacts relevant to the performance of riverine plants has been conducted with the hope that it will help researchers to identify the variables that are most important in impacting riverine vegetation as well as the expected changes in riverine communities under hydropeaking. Second (Objective 2; task 3), two approaches for assessing the effects of hydropower dam operations on within-day flow (i.e. instantaneous) regimes across multiple dams and rivers have been developed: one analytical, based on a bunch of ecologically meaningful metrics, and the other graphical. Both provide a full description of the short-term variation of flow in free-flowing rivers and rivers exposed to hydropeaking and enable the quantification of the deviation of the characterized altered short-term flow regime from the unaltered state. The software InSTHAn (Indicators of Short-Term Hydrological Alteration) has been created to enable the easy and fast characterization and alteration assessment of the instantaneous flow regime from rivers subjected to hydropeaking. Third, the hydropeaking effects on the recruitment and performance (Objectives 3 and 4; task 4) of several riparian species from northern Sweden have been studied, based on experimental set-ups in the field and greenhouse. The most threatened life-history stages (e.g. germination and establishment) have been identified, as well as the tolerance limits of the studied riparian plants to hydropeaking. Fourth (Objective 5; task 5), ecological and economic trade-offs resulting from the operation of a selection of hydropower plants in Spain have been analyzed and the best operational measure in the form of environmental flow regime have been identified for the study cases (see work plan in Annex 2).

Three scientific articles directly derived from the above mentioned activities and results have been already published in prestigious peer reviewed journals, and four extra manuscripts will be promptly submitted (see next Section for details):
Objective 1:
- The effects of hydropeaking on riverine plants: a review. Biological Reviews
Objective 2:
- Characterizing effects of hydropower plants on sub-daily flow regimes. Journal of Hydrology
- A graphical approach to characterize sub-daily flow regimes and evaluate its alterations due to hydropeaking. Science of the Total Environment
- Software for characterization and impact assessment of short-term flow and water level regimes. To be submitted to Environmental Software and Modelling in October 2017
Objectives 3 and 4:
- Manuscript on the effects of hydropeaking on recruitment and performance of riparian plants based on the field experiments. In preparation
- Manuscript on the effects of hydropeaking on recruitment and performance of riparian plants based on the greenhouse experiments. In preparation
Objective 5:
- Balancing economic gains and ecological losses: the key to the best environmental flow method selection. To be submitted to Rivers Research & Applications in November 2017

In addition, the registration of the intellectual property of the software InSTHAn will be requested in October (coinciding with the submission of the corresponding paper from the Objective 2) at the Spanish Office of Registration of Intellectual Property (Spanish Ministry of Education, Culture and Sports). Other outcomes from the project include three Bachelor Theses and one Master Thesis led by Bejarano MD which are the foundations of the corresponding in-preparation papers from the Objectives 3 and 4:
- Impacts of hydropower dams operations on plants: a greenhouse experiment on the response of germination and performance and survival of plant seedlings to direct and indirect effects of hydrological alterations resulting from hydropower dam operations
- How do functional riparian groups from northern Sweden respond to hydropeaking? Short-term indoors study on germination, mortality and performance of Swedish riparian species from different species groups subjected to water treatments mimicking hydropeaking
- Do riparian plant functional groups from northern Sweden respond differently to hydropeaking?
- Riparian vegetation responses to hydropeaking: experimental study on germination and performance of plants along rivers regulated by hydropower dams in northern Sweden

Several scientific papers indirectly related to the RiPeak project have been also published or are currently under review (see next Section for details):
- Traits of riparian woody plants responding to hydrological and hydraulic conditions: a northern Swedish database. Ecology
- Riparian plant guilds become simpler and most likely fewer following flow regulation. Journal of Applied Ecology
- Impacts of flow regulation on guilds of riparian woody plants in Mediterranean Europe: cases from northern and central Portugal. Under revision in Journal of Applied Ecology
- Legacy effects of floods on the establishment of riparian plants. Under revision in Journal of Ecology

Following global warming, policy makers promote hydropower as a clean and renewable energy source. Hence, the challenge for industry and society involves maximizing hydropower production and minimizing ecological impacts. RiPeak highlights the need for greater knowledge about the environmental constraints of hydropower generation. It is the first research project providing scientific information on hydropeaking and riverine vegetation, which may be used to quantify and predict ecological impacts on river margins derived from different hydropeaking regimes. Ultimately, this scientific knowledge increases our ability to preserve, restore and manage in a sustainable way the margins of hydroelectric rivers, both upstream and downstream from the power facilities.