Operational constraints of mini-hidropower schemes considering brown trout habitat.

Isabel Pragana, Isabel Boavida, Rui Cortes, António Pinheiro

Friday 3 july 2015

8:45 - 9:00h at Europe 1 (level 0)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology

Parallel session: 14G. Environment - Renewable

Hydropeaking is seen as one of the major river impacts, affecting the natural flow regime and the biotic integrity. This occurs due to hydropower plant operation when high discharges are made during high electricity consumption periods, severely affecting the aquatic ecosystem. The intensity, frequency and persistence of hydropeaking events often place an intolerable stress on fish over all life-stages thus interfering with the population success. To contradict this tendency, either structural or operational mitigation measures have been proposed. Structural measures may include the alteration of the river bed morphology, construction of lateral bays, or the introduction of macro roughness in the river banks. Operational measures are related to the hydropower plant management/production, and may be the reduction of the peak flows or the adjustment of the peak flows during high electricity consumption periods. Usually, structural measures are selected over the operational ones due to the economic impacts on the electricity producer, which may turn ecological conservation unfeasible. Therefore, understanding the impacts of operational measures over the economics of electricity production is paramount in order to select solutions that fit both interests. The present study investigates the effects of a mini-hydropower plant in the fish habitat of brown trout (salmo trutta) considering different operational scenarios. Thus, River2D was applied to the river reach downstream the Ermida hydropower dam in the Carvalhosa stream, Northern Portugal, to simulate the peak flows’ hydrodynamic patterns. The fuzzy sets and rules were developed for juvenile and adult life-stages of trout and habitat simulations were carried out in the Casimir Fish 2D. Accordingly different operational scenarios were developed considering the habitat availability results, how the hydropeaking was influencing quantity, quality and location of different habitats, and the power production periods according to the cost of the electricity. Results from this study will assist water managers to adapt hydropeaking regimes in order to reduce ecological impact without neglecting economic benefits.