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Downstream Environmental Effects of Ralco and Pangue Dam Operations: Changes in Habitat Quality for Native Fish Species, Biobio River, Chile

Author(s): Garcia Alex; Jorde Klaus; Habit Evelyn; Parra Oscar

Linked Author(s): Klaus Jorde, Alex Garcia

Keywords: Fish habitat modeling; CASiMiR; Operational losses; Hydropeaking events

Abstract: The first large dams and reservoirs, Pangue and Ralco, have been built on the Biobio River in Central Chile, and are fully operational since 1997 and 2005, respectively. The operation of these dams and reservoirs, mainly for hydropower generation, has dramatically altered the hydrological regime downstream Pangue in two ways. Firstly, the annual regime has been altered and moderated because of the annual storage capacity of Ralco. Secondly, strong daily fluctuations are overlapping the altered mean flows since Pangue is used for hydropeaking. The endemism of Chilean fish species is due to the geography, the climate, and the relatively isolated watersheds, but very little is known about their ecological and social values. On this study, eight native fish species in a representative reach of the Biobio River were studied and their preferred habitats were surveyed and characterized. A hydrodynamic model was developed for a reach of river and linked to the fish habitat simulation model CASiMiR. “Fuzzy rules” and “fuzzy sets” were developed describing habitat use of the native fish species. CASiMiR was then used to simulate how physical habitat conditions have changed due to the operation of the dams. Results show how overall habitat quality, expressed as Weighted Usable Area and Hydraulic Habitat Suitability, is changed and fluctuating due to the reservoirs operation and how the daily hydropeaking is influencing quantity, quality and location of different habitats.


Year: 2007

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