Is Hydroelectric Power really that Green?

Three Gorges Dam, China 

The Three Gorges Dam is the world largest hydroelectric power dam. This magnificent structure that dams the Yangtze river of China signifies the rise of hydroelectric power dams. In countries like Norway and Nepal, over 90% of electricity generated are from hydroelectric sources. In the United States, China and India, hydroelectric power constitutes around 15% of total electricity produced (Data.worldbank.org, n.d.). In this blog post, I will explore the benefits of hydroelectric dams as well as the potential harm it can bring about to the environment. 

Benefits of Hydroelectric Dams 

Hydroelectric dams can reduce the cost of electricity. They are usually quite durable and can possibly last for over 50 years with regular maintenance (Hydroelectricity Fact Sheet, 2012). While the initial cost of building the dams can be very large, the costs can be spread out over a long time and hence may appear to be a good investment for many countries. As countries make the switch over to hydropower, their reliance on oil and natural gas can be reduced. The volatility in prices of commodities such as oil and natural gas can lead to spike in the cost of electricity. By avoiding these large fluctuations that arise from commodities, countries feel more assured and costs of electricity can be stabilised and reduced. 

Another benefit from hydroelectric dams is the reduction in carbon dioxide emissions. This is because the use of hydropower ,unlike burning of fossil fuels, does not release carbon dioxide emissions. Water is used to turn the turbines of the generators to produce electricity. According to a study done by Paul Scherrer Institut and the University of Stuttgart, hydroelectricity release the least amount of greenhouse gas emissions when compared to other sources such as wind and nuclear energy (Dones et al., 2005). Hence, many countries are likely to adopt this strategy to produce electricity to reduce carbon emissions in an attempt to slow down global warming. 

Environmental Impacts of Hydroelectric Dams 

However, dams can possibly lead to increased greenhouse gas emissions too. The building of dams can lead to the formation of small reservoirs. Decomposition of organic matter in deep waters leads to a depletion of dissolved oxygen. This situation is worsened as waters in the reservoirs do not mix well and the dissolved oxygen in deep waters will not be replenished. Consequently, the reservoirs contain little or no dissolved oxygen. In low oxygenated waters, bacterial methanogenesis and denitrification results in the production of methane and nitrous oxide respectively (Friedl and Wüest, 2001). Both methane and nitrous oxide are greenhouse gases. It has been noted that methane is a more potent greenhouse gas than carbon dioxide. Methane has 72 times greater Global Warming Potential (GWP) as compared to carbon dioxide over 20 years (IPCC, 2007). The risks of increased release of potent greenhouse gases such as methane and nitrous oxide suggest that global warming may be aggravated, enhancing the detrimental consequences felt. 

Furthermore, dams can result in great loss of biodiversity. The presence of dams acts a physical barrier, segmenting the river. Spawning grounds for fishes are reduced and habitats are lost as marine creatures are no longer able to travel upstream. As a result, fish populations tend to decrease (Nilsson et al., 2005). Many dammed rivers may also support migratory species. Carex, located in the vicinity of the Three Gorges Dam in China, has been reduced in size to accommodate the dam. This area is particularly important because it provides food and water for the winter migratory birds (Xie et al., 2015). With a reduced land area, there will undoubtedly be lesser food and water supplies available for these migratory birds. It is plausible that there would be insufficient resources to support the population of migratory birds. It is noteworthy that these birds play a key role in pollination as well as controlling pests’ population. A decline in their population can possibly adversely impact biodiversity and upset global food chains. It can be observed that construction of dams do not only threaten local terrestrial species but can also have a greater impact on international biodiversity. 

Undeniably, hydroelectric power is still a much better option than using non-renewable energy such as coal and natural gas as the amount of greenhouse gas emissions are likely to be lower. While hydroelectric power should be encouraged, tighter regulations can be imposed in surveying the location for the building of dams and plans on how to reduce the damage done to the local ecosystem should be made. 

References 

Data.worldbank.org,. Electricity production from hydroelectric sources (% of total) | Data | Table. Retrieved 9 October 2015, from http://data.worldbank.org/indicator/EG.ELC.HYRO.ZS

Dones, R., Heck, T., Bauer, C., Hirschberg, S., Bickel, P., & Preiss, P. (2005). ExternE-Pol Externalities of Energy: Extension of Accounting Framework and Policy Applications.

Friedl, G., & Wüest, A. (2002). Disrupting biogeochemical cycles – Consequences of damming. Aquatic Sciences, 64, 55-65. doi:1015-1621/02/010055-11

Hydroelectricity Fact Sheet. (2012) (1st ed.). Retrieved from https://www.cleanenergycouncil.org.au/technologies/hydroelectricity.html

Nilsson, C. (2005). Fragmentation and Flow Regulation of the World's Large River Systems. Science, 308(5720), 405-408. doi:0.1126/science.1107887

Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.) (2007) Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA

Xie, Y., Yue, T., Xin-Sheng, C., Feng, L., & Zheng-Miao, D. (2015). The impact of Three Gorges Dam on the downstream eco-hydrological environment and vegetation distribution of East Dongting Lake. Ecohydrol. Ecohydrology, 8(4), 738-746. doi:10.1002/eco.1543