Water resources and sustainability

Water and energy

According to Kelman et al (2006), the Brazilian hydroelectric park is one of the largest in the world, both in absolute and relative terms. Despite the diversification of energy sources (thermoelectric, wind and others) in recent years, 81.7% of electricity production in Brazil comes from hydroelectric generation (EPE 2012). Hydroelectric power plants were built on all major rivers in Southeast Brazil and on rivers in the Amazon. There is also expansion of the construction of PCHs (Small Hydroelectric Power Plants of up to 50 megawatts) in many regions of the country.

In 2002, the HPP (Hydroelectric Power Plants) in Brazil produced 313,811 gigawatts, which at the time represented 88.8% of the total. Although current data show a diversification in the energy matrix with the contribution of hydroelectric plants in 75%, it is verified that there is an increase in the contribution of thermoelectric plants to energy production. The Amazon Basin currently represents the greatest hydroelectric potential in the country. The estimated potential is 258,420 MW and only 24% of this potential has already been used (Source EPE 2012).

The construction of hydroelectric plants presents major socio-environmental problems for some projects, because depending on the location and size (volume, flooded area), there are upstream and downstream impacts. The construction itself already impacts on water systems, on the main rivers and in tributaries and hydrographic basins. However, with accurate and predictive studies, impacts can be assessed and minimized, making the project sustainable and less impactful. The construction and engineering of reservoirs in the Brazil present considerable advances in relation to the sustainability and future management of these artificial systems (Braga et al 1997).

It is possible to summarize the impact of the construction of dams for hydroelectricity in four main problems: impact on the flow of the river, transforming the aquatic ecosystem from lotic to lentic and changing the essential conditions of operation of natural systems; impacts on aquatic and terrestrial biodiversity, fish fauna, fish migrations, and the geographic distribution of aquatic organisms; impacts on regional socioeconomic, with influences on the hydrosocial cycle and changes in the dynamics of the regional economy, such as fishing, navigation, recreation and tourism; and downstream impacts: downstream rivers are impacted by changes in water quality and in biogeochemical and socioeconomic cycles.

However, the construction of hydroelectric plants in Brazil has positive effects: boosting the country’s economy; encouragement of local and regional employment and income generation; possibilities for expanding the use of water resources for navigation, agriculture, tourism and recreation; construction of local and regional infrastructure: schools, sewage treatment plants, roads, improvement in the health system and residential areas with better services and adequate basic sanitation. Therefore, the generation hydroelectric power plant in Brazil, even considering the impacts, was positive for the economic and social development of the country.

From a research and management perspective, it is essential to advance in comparative studies of reservoirs. Such studies, already started a long time ago (Agostinho et al 2007, Tundisi & Matsumura-Tundisi 2008, Tundisi & Matsumura-Tundisi 2012), are essential to expand the database and allow interaction between basic scientific research and management (Tundisi & Straskraba 1999). Brazilian dam engineering has already expanded some fundamental concepts in construction, with effects on ecological functioning and water quality control: shorter retention time (reservoir retention time is a function of essential force in water quality management), higher number of openings for the exit of water, smaller volume and smaller flood area. Many processes Control operations were incorporated into the electricity generation system, in order to reconcile water quality upstream and downstream (Straskraba et al 1993, Jorgensen et al 2005).

It should also be considered that the appropriation of water resources for hydroelectricity in Brazil must take into account the natural disposition of the main rivers and tributaries. The location of dams or waterfalls of dams needs engineering and ecological hydrological foundations, in such a way that vital processes such as the evolutionary capacity of the system are preserved together with the generation hydroelectricity, efficiently and viable. Additionally, reservoir operation and management systems need scientific inputs – Limnology, Aquatic Biology, Biogeochemistry – to obtain better results and less impact. The conciliation of techniques of ecohydrology and ecotechnologies (Straskraba & Tundisi 2008, Jorgensen et al 2012) with the constructive characteristics is fundamental.

For the strategic reservoirs in the Amazon, it is vital to expand this vision. It is necessary to preserve rivers in the Amazon Basin in totum to conserve the system’s evolutionary capacity and protect the aquatic and terrestrial megadiversity in this basin (Tundisi 2007a, Tundisi et al 2013).

As for the emission of greenhouse gases, ongoing studies (Correa et al. 2011) show that this emission is below those emitted by thermoelectric plants used for the generation of electricity (Abe et al 2009), except in some cases exceptional in Amazon dams (Santos & Rosa, Kemenes et al 2007).

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