The past few years have witnessed an increase in population and a subsequent increase in need for food, water, and power. Concurrently, dams, a prominent type of water infrastructure, have also increased in number, from 9,056 in 1960 to 32,473 in 2010 and are expected to continue increasing (Chen, Shi, Sivakumar, & Peart, 2016). Dams provide a wide range of benefits to the environment and humans, including providing water for drinking and irrigation, hydropower generation, food security, flood control, reduction of natural disasters, transportation, recreation, aquaculture, and tourism (Chen et al., 2016; McCartney, 2009). Although dams have several benefits, they are seen to be double-edged swords in the countries they are built in through their negative impact on the environment and public health via change in water quality, bioaccumulation in fish and humans, and increased malaria prevalence. The aim of this essay is to shed light on the nature of dams’ negative impacts on the environment and human health.
The construction of dams results in water quality alteration. The presence of a dam obstructs the natural flow of rivers resulting in relatively stagnant water (McCartney, 2009). This becomes increasingly problematic with the rise in industries and the pollution that comes with it and winds up in various bodies of water, including reservoirs created by dams. In the latter case, the stagnant nature of water imposed by dams results in the accumulation of pollutants in these waters which would have otherwise been diluted in naturally flowing waters. Thus, dams break down the continuum of water flow, damaging water quality with the pollutants it gathers (Wei et al., 2009). For instance, in Ghana’s Volta Reservoir, water chemistry change due to a surge in toxic metals in water was found to be associated with dam construction (McCartney, 2009). The resultant pollution has drastic implications not only on humans who rely on reservoirs, but also on the organisms living in the affected waters.
With the aforementioned water quality change, heavy metal accumulation occurs, serving as an adverse environmental and health impact. Reservoirs have higher concentrations of heavy metals due to the construction of dams which prevent the self-purification water process (Zhao, Liu, Deng, Dong, & Wang, 2013). As such, the natural habitat of a wide variety of organisms, like fish, is compromised, whereby they ingest pollutants, introducing them to their bodies. Not only that, but also fish respire through the diffusion of water, now polluted, across the gills increasing the pollutants within the fish. This harms the fish through disruption of various organ functions, gill collapse, toxicity, and cancer development (Authman, Zaki, Khallaf, & Abbas, 2015). This process along with the food chain cycle, eventually reaches humans who consume these fish (Rzymski, Niedzielski, Klimaszyk, & Poniedzia?ek, 2014). This process is known as bioaccumulation and can be magnified, causing detrimental effects on an individual’s health (Streit, 1992). Metals which accumulate in fish include, but are not limited to, arsenic, barium, cadmium, chromium, mercury, and selenium, cause a wide range of adverse health effects on humans, ranging from vomiting and diarrhea, to muscle and bone weakness to lung damage, neurological problems and different cancers (Martin & Griswold, 2009). This shows that people are being unjustly exposed to a wide range of different diseases because they consume fish from reservoirs, breaching the Belmont Report’s Beneficence Principle (Belmont Report, 1979), whereby dams fail to reduce risks, while producing benefits. For example, in South India’s Anaikarai Dam, mean concentrations of chromium, manganese, and iron in muscle tissue of different fish species were over the limit accepted by the Food and Agriculture Organization (FAO) and World Health Organization (WHO) (Bhuvaneshwari, Mamtha, Selvam, & Rajendran, 2012). Also, in Quebec, Canada, Cree Indians were found to have higher levels of mercury than the levels recommended by WHO due to consumption of fish from reservoirs (McCartney, 2009).
Another negative health impact dams cause is increased malaria prevalence. As a result of the impounding water in the reservoir, dams have been associated with increasing different non-communicable diseases, including malaria (Duflo & Pande, 2007). The reservoirs, puddles, irrigation areas, and regions close to the dam provide areas of standing water, which are optimal breeding and development sites for the malaria vector, Anopheles (Duflo & Pande, 2007; Keiser et al., 2005). Dams alter the ecosystem, atmospheric system (increased humidity), and hydrological system (change in water flow, chemistry, and current), in ways which are optimal for the Anopheles larvae, enhancing their development and longevity and increasing their number. This aids in malaria transmission whereby the mosquito vectors will feed on the people living in close proximity to the dam and irrigation areas, and on workers there (Keiser et al., 2005). This unjustly exposes individuals to malaria, breaching the Belmont Report’s justice principle (Belmont Report, 1979), whereby people living in close proximity to dams are at a higher risk of contracting malaria compared to people living farther away. For example, puddles created by the Ethiopian Koka Dam and its reservoir served as optimal breeding sites for Anopheles, with malaria prevalence being 1.5 and 2.3 times higher for individuals living in close proximity to the reservoir compared to those living between 3 to 6 km and 6 to 9 km, respectively, from the reservoir (Kibret, Lautze, Boelee, & McCartney, 2012; Lautze et al., 2007).
Although the original purpose of dams initially seems beneficial to the environment and health, it has been also found to do just the opposite. A dam is a double-edged sword to both environment and human health in the country it is built in, whereby its negative impacts are evident through water quality alteration, bioaccumulation in fish and humans, and increased malaria prevalence. The negative risks dams pose on the environment and human health must not be disregarded. Dams exacerbate both environmental and human health through a domino effect, starting off with the deterioration in water quality, to its effect on fish and Anopheles, to ultimately threatening human health.