A conceptual framework for hydropeaking mitigation.
Hydropower plants are an important source of renewable energy. In the near future, high-head storage hydropower plants will gain further importance as a key element of large-scale electricity production systems. However, these power plants can cause hydropeaking which is characterized by intense unnatural discharge fluctuations in downstream river reaches. Consequences on environmental conditions in these sections are diverse and include changes to the hydrology, hydraulics and sediment regime on very short time scales. These altered conditions affect river ecosystems and biota, for instance due to drift and stranding of fishes and invertebrates. Several structural and operational measures exist to mitigate hydropeaking and the adverse effects on ecosystems, but estimating and predicting their ecological benefit remains challenging. We developed a conceptual framework to support the ecological evaluation of hydropeaking mitigation measures based on current mitigation projects in Switzerland and the scientific literature. We refined this framework with an international panel of hydropeaking experts. The framework is based on a set of indicators, which covers all hydrological phases of hydropeaking and the most important affected abiotic and biotic processes. Effects of mitigation measures on these indicators can be predicted quantitatively using prediction tools such as discharge scenarios and numerical habitat models. Our framework allows a comparison of hydropeaking effects among alternative mitigation measures, to the pre-mitigation situation, and to reference river sections. We further identified key issues that should be addressed to increase the efficiency of current and future projects. They include the spatial and temporal context of mitigation projects, the interactions of river morphology with hydropeaking effects, and the role of appropriate monitoring to evaluate the success of mitigation projects.
Eawag, Swiss Federal Institute of Aquatic Science, Surface Waters - Research and Management, Seestrasse 79, 6047 Kastanienbaum, Switzerland; University of Applied Sciences and Arts of Southern Switzerland, Institute of Earth Sciences, Campus Trevano, 6952 Canobbio, Switzerland; Wasser-Agenda 21, Überlandstrasse 133, 8600 Dübendorf, Switzerland. Electronic address: andreas.bruder@supsi.ch.
Andreas
A
Bruder
Zurich University of Applied Sciences, Institute of Natural Resource Sciences, Grüental, 8820 Wädenswil, Switzerland.
Diego
D
Tonolla
Kraftwerke Oberhasli AG, 3862 Innertkirchen, Switzerland.
Steffen P
SP
Schweizer
Wasser-Agenda 21, Überlandstrasse 133, 8600 Dübendorf, Switzerland.
Stefan
S
Vollenweider
Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany.
Simone D
SD
Langhans
Eawag, Swiss Federal Institute of Aquatic Science, Surface Waters - Research and Management, Seestrasse 79, 6047 Kastanienbaum, Switzerland; Physics of Aquatic Systems Laboratory - Margaretha Kamprad Chair, EPFL-ENAC-IIE-APHYS, 1015 Lausanne, Switzerland.
Alfred
A
Wüest
Discharge fluctuations; Ecological indicators; Functional indicators; Hydroelectricity; Multiple stressors; Prediction tools; River restoration