Energy production has experienced numerous landmark changings thought the century. Although there is no perfect solution found in terms of satisfying the needs for energy resources and mitigating its environmental and social impact, hydropower generation is considered a renewable energy source and alternative to fossil fuel combustion. Hydropower generation has experienced significant advancement throughout its history. However, the principle of its work is rather comprehensive. The energy of falling water is employed to turn the turbine, which is connected to the electricity generator. Furthermore, electricity is supplied through grids to industrial or domestic units. In most cases dams are utilized for the purpose of discharging more water into the turbine, thus, generating more electricity. Secondly, it provides reservoir for water storage and increase the height of the falling water. By achieving this height the velocity of the falling water is speeded up, while providing more generated electricity (ReVelle & ReVelle, 1992).
The following Figure 1 illustrates the simple principle of hydropower generation and its basic elements.
Figure 1 – The elements of hydropower plant (ReVelle & ReVelle, 1992)
The construction of hydropower station has its side-effects, both positive and negative. From the standpoint of covering energy demand its capability is rather high for satisfying the residential and industrial needs, although hydropower generation is usually utilized to cover peak loads in electricity generation curve. While the basic generation is satisfied by thermal power generations, which are not so flexible and manoeuvrable to switch on and off to cover peaks of electricity generation. For this purpose hydropower is a perfect component in the electricity generation system. Regarding its economic viability, the capital costs are estimated to be huge, while the operation costs are very low, where no specific labour or materials are required. Therefore, it is reasonable to make a right trade-off between capital expenditures and operation costs.
Although this type of energy production does not jeopardize the society as much as for instance in the case of nuclear power or fossil fuel combustion, there are still some ecological and social impacts, which are under ongoing research. On the countrywide level, an operation of hydropower plant is beneficial, since it does not entail greenhouse gas emissions, thus, does not contribute to the potential warming and climate change. Besides, it provides opportunities for employees, which stabilizes the country's economy. In the local and regional scale there are some social disturbances, which are caused by the reservoirs. They can seize a huge part of the land, which could be places for living or for growing food in the fields. Alternatively, hydropower can cause less problems, if it is allocated on the mountain river. In this case the velocity of the falling water is naturally high and produce a sufficient volume of energy.
Following the basic principle of hydropower generation it is necessary to underline that different types of hydropower stations create different effects, both environmental and social. Table 1 is dedicated to show those effects.
The main impact on environment is described by (Edenhofer et al., 2011), ''All hydroelectric structures affect a river's ecology mainly by inducing a change in its hydrologic characteristics and by disrupting the ecological continuity of sediment transport and fish migration through the building of dams, dikes and weirs'' (p.462). As the outcomes of IEA reports there were several influential aspects to consider. First of all, hydropower modifies the river hydrology. The discharge of water changes the flow regimes, temperature and the water levels. This may create a negative effect on natural aquatic and terrestrial habitants in the river and on the shore, where the sudden water flow can drown their nests.
Another big issue concerning an effect of hydropower is creating a reservoir, which significantly changes the mode of river. It transforms the ecosystem of the river by changing the fast-growing course of the flow to still-standing water. This creates a danger of extinction of those fish, who require fast water flow for living. From another side, such construction as reservoir requires specific treatment of the shorelines. As far as the water level is changed, it created the erosion of the shores, that is why some protective structures of bioengineering need to be implemented.
Generally, another concern is risen in the question of water quality, which can also be diminished in still-water body. However, to consider this aspect many factors need to be evaluated, such as the depth of the reservoir, climate, river morphology, rapidity of impoundment and so on. Alongside with the quality of water, hydropower also poses danger in the atmosphere because of the methane emissions. It does not generate the direct emissions, but it emits methane, when plant decompose in the flooding caused by a dam (EnergyBC, 2012).
It is also determined after conducted researches the role of hydropower to biodiversity of mammals, birds and fish. There are some effects, which are distinguished (Edenhofer et al., 2011):
- habitat changes,
- geological and climate changes,
- direct mortality, and
- increased human use of the are.
Considering the real examples of an existing power station, Hydro-Quebec maintains continuing research of the environmental effect of hydropower and documents the status of protection biodiversity, water and soil and sustainability. It is claimed that biodiversity is going through some changings, where a range of native species are moving northward, because they had some troubles to survive there. Though about 60 000 species have been recently inventoried in Quebec. A number of precautious measures have been implemented to protect biodiversity, as managing shrub screens and ponds, as well as limit the constructions along the shorelines. The area is still imposed to contamination due to the operation of power utilities, which are currently under investigation. 1.76 million litres of drinking water were provided by an administrative refurbishment program (Quebec, 2014).
Another example of environmental impact of the hydrology is provided by the world's biggest hydropower plant, the Three Gorges Dam in China. An environmental impact assessment has been conducted to create a benchmark of its operation since the year of 2006 taking into consideration several environmental indicators. The outcomes of the assessment estimated the reduction level of carbon emission to be around 406.7 Mt from 2003 to 2007 by the operation of hydropower station as a substitute of fossil fuel combustion. One of the crucial factors was a level of human displacement, which was actually amounted to 1.25 million people. This has effected in a rapid urbanisation and a loss of settled places by rural dwellers. A water quality was also assessed. While pollutant concentration was increased in the region and the river flow slowed down and turned into still-water body, such affect as eutrophication has occurred, where algae bloom in the reservoir area has flourished. Therefore, the water quality is likely to be diminished since 2003. Additionally, riverbed erosion effects the stability of embankment significantly and requires some bioengineering constructions to be further implemented (Xibao Xu, 2013).
Another environmental assessment is applied here for the Vaca Hydroelectric Dam in Belize City. First, an initial construction has caused some irreversible changes to the terrain because of the road construction, abutment of the dam, blasting and so on. There was also an emission of dust, vibration and noise in the local scale. An inundation length upstream has been assessed as 6.5 km in total. As far as there was no significant sedimentation in the watershed, the water quality is not bound to any drastic diminishing. However, it did effect the surface water and river estuary, which is a typical effect of the dam construction (Solutions, 2006 ).
A tragic example of employing hydropower is an accident of Sayano-Shushenskaya hydropower station on August 17, 2009 in Khakassia, Russia, where the second turbine broke apart. This catastrophe is described by (Staff, 2012) as ''The turbine hall and engine room were flooded, the ceiling of the turbine hall collapsed, 9 of 10 turbines were damaged or destroyed, and 75 people were killed. The entire plant output, totalling 6 400 MW and a significant portion of the supply to the local grid, was lost''.
References
Edenhofer, O., Pichs-Madruga, R., Sokona, Y., Seyboth, K., Kadner, S., Zwickel, T., . . . von Stechow, C. (2011). Renewable Energy Sources and Climate Change Mitigation: Special Report of the Intergovernmental Panel on Climate Change: Cambridge University Press.
EnergyBC. (2012). Large Hydro. from http://www.energybc.ca/profiles/largehydro.html
Quebec, H. (2014). Environmental impact management. from http://www.hydroquebec.com/sustainable-development/energy-environment/environmental-impact-management.html
ReVelle, P., & ReVelle, C. (1992). The Global Environment: Securing a Sustainable Future: Jones and Bartlett.
Solutions, E. (2006 ). ENVIRONMENTAL IMPACT ASSESSMENT. VACA HYDROELECTRIC PROJECT, CAYO DISTRICT BELIZE (pp. 313). Kingston, USA.
Staff, E. (2012). Sayano-Shushenskaya Hydroelectric Power Station Accident from http://engineeringfailures.org/?p=703
Xibao Xu, Y. T., Guishan Yang. (2013). Environmental impact assessments of the Three Gorges Project in China: Issues and interventions. EARTH-SCIENCE REVIEWS, 124, 115–125.
