Modify hydropeaking

Modify hydropeaking

General description

The production of electricity by hydropower plants is often implemented to satisfy peaks in electricity demand. For this reason these plants work intermittently, creating periodic and extremely rapid and short-term fluctuations in flow in the receiving water body. These fluctuations are called hydropeaking and usually show a marked weekly and daily rhythm (http://wiki.reformrivers.eu/index.php/Hydropeaking). Therefore, understanding the ecological effects of hydropeaking is important for a sustainable management of streams. Negative effects due to large fluctuations in flow (e.g. changes in sediment regime, habitat quality, the reduction of benthic invertebrate and fish biomass and shifts in species composition) could be altered by constructional and/or operational modifications. The following article gives an overview of measures reducing negative ecological effects associated with hydropeaking.

IMPORTANT NOTE: Prior to the implementation of measures comprehensive investigations are recommended to assess negative ecological effects due to hydropeaking at the regional scale and to define ecological objectives.

Applicability

There are certain modifications to decrease disturbances in a stream due to hydropeaking. Here, we distinguish between (i) constructional and (ii) operational modifications (compare Bruder et al. 2012).

1. Water could be stored before being passed into the stream in the long term, e.g. by using interconnected flood plains, artificial pools, and channels. The water could also be bypassed into a lake or bigger stream. Morphological restoration of the downstream reach could additionally support mitigation effects because of a bigger stream width, the reconnection of side-arms and the creation of pools. Especially pools and side-arms can be used as a refugium for different species during low and/or high flow situations. We suggest combining morphological restoration with other measures (constructional or operational) to achieve positive results. Only restoring the downstream reach might not be sufficient.
2. Sustainable operational measures mean an adapted treatment of hydropower plants to decrease flow peaks.

The choice of measures can depend on national guidelines. E.g. constructional measures could be favored since they ensure same efficiency in terms of power production. For the construction of storage zones (must be appropriate in size/volume) sufficient space in the landscape is needed and might therefore be a constrain.

Expected effect of measure on (including literature citations):

Constructional and operational measures aim at decreasing negative ecological effects of hydropeaking: changes in sediment regime and habitat quality, strong fluctuations in water level, water temperature, nutrient load and oxygen content or increased turbidity. Furthermore, negative effects on biota (fish, invertebrates, plants), e.g. drift of organisms, reduced abundance and biomass, reduced diversity or changes in species composition should be avoided. Please compare a list of effects due to hydropeaking available on: http://wiki.reformrivers.eu/index.php/Hydropeaking. There are some studies (e.g. Armanini et al. 2014, Bruder et al. 2012 - in german) and reports (e.g. Schmutz et al. 2013) dealing with effects of mitigation measures on stream biota. Furthermore, there are some experiments running in the Alpine regions (Austria) focusing on benthic invertebrates. The group is using mesocosm experiments to test for effects of different flows on benthic invertebrates, They are also combing different flow situations with temperature fluctuations (multiple stress). The study is part of the MARS project (Managing Aquatic ecosystems and water Resources under multiple Stress; http://www.mars-project.eu/). By today the results have not been published (October 2015).

Temporal and spatial response

Not available.

Pressures that can be addressed by this measure

• Hydrological regime modification
• Reservoir flushing
• Hydropeaking

Cost-efficiency

Not available.

Case studies where this measure has been applied

• Manzanares

Useful references

• Armanini, D.G., A. Idigoras Chaumel, W.A. Monk, J. Marty, K.E. Smokorowski, M. Power, and D.J. Baird (2014). Benthic macroinvertebrate flow sensitivity as a tool to assess effects of hydropower related ramping activities in streams in Ontario (Canada). Ecological Indicators, 46, 466–476.
• Bruder, A., Vollenweider, S., Schweizer, S., Tonolla, D. & Meile, T. (2012): Schwall und Sunk: Auswirkungen auf die Gewässerökologie und mögliche Sanierungsmassnahmen. «Wasser Energie Luft» – 104. Jahrgang, 2012, Heft 4, CH-5401 Baden. (in German)
• Schmutz S., Fohler N., Friedrich T., Fuhrmann M., Graf W., Greimel F., Höller N., Jungwirth M., Leitner P., Moog O., Melcher A., *Müllner K., Ochsenhofer G., Salcher G., Steidl C., Unfer G., Zeiringer B. 2013: Schwallproblematik an Österreichs Fließgewässern – Ökologische Folgen und Sanierungsmöglichkeiten. BMFLUW, Wien. Available: http://www.bmlfuw.gv.at/dms/lmat/wasser/wasser-oesterreich/plan_gewaesser_ngp/umsetzung_wasserrahmenrichtlinie/schwallstudie/Schwallbericht0/Schwallstudie.pdf