Author(s): Isabel Boavida; Jose Maria Santos; Maria Teresa Ferreira; Antonio Pinheiro
Linked Author(s): José Maria Santos, António Pinheiro
Keywords: Hydropeaking; 2D habitat models; WUA; Fish preferences; Luciobarbus bocagei
Abstract: Hydropower energy is a renewable resource and the actual trend is to gain more and more importance following the population growth and the rise of global awareness to the climate change. Moreover, in order to store the surplus of electricity produced by windmills, more and more pumped storage schemes are being constructed. The respective powerplants are mostly used for peak production, which increases the frequency of hydropeaking regimes downstream. Rapid fluctuations of the river flow occur naturally according to seasonal fluctuations, likewise in Mediterranean rivers, imposing changes in food availability and predator encounters. However 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. Therefore, understanding how hydropeaking influences both habitat availability and population dynamics is a crucial point to help guiding hydropower managers towards more sustainable practices. Furthermore, relatively few studies have described the quantitative effects of hydropeaking flows on fish habitat, especially for cyprinid species because of their lack of economic interest. This is highly unfortunate, since cyprinid species are an important biological component of fish assemblages and some of them are critically endangered due to human-induced habitat modifications. The hydraulic-habitat models represent a powerful tool to assist hydropower management, once they can be used to assess and quantify the long-term effects of hydropeaking on different life-stages of organisms based on ecologically tolerable values and physical parameters. The River2D model was created with the purpose to investigate how fish habitat change with the flow and river bed characteristics. This 2D finite element model simulates the hydrodynamic conditions in the studied reach and estimates the potential value of habitat for the requirements of different species and development stages by computing the weighted usable area (WUA) for each simulated discharge. The present study investigates the effects of hydropeaking in the habitat of Iberian barbel (Luciobarbus bocagei) a native fish species of the Iberian Peninsula, providing comprehensive information on the response of this cyprinid species to hydropeaking. Thus, Habitat Suitability Curves (HSC) were developed for juvenile and adult life-stages of barbel and the River2D was applied to a river reach downstream the Pracana hydropower dam in the Ocreza river, Mid-Eastern Portugal, to simulate how physical habitat conditions vary with powerhouse operation. Results show how the habitat availability, expressed as WUA, changes with flow fluctuations and how the daily hydropeaking is influencing quantity, quality and location of different habitats. The results from this study will help water managers to regulate hydropeaking operation in order to minimize ecological impact.
Year: 2013