Kingdoms are established and vanquished, thrones overthrown and political regimes rise to fall. In all this, one nation remains unaffected. A nation bound by aspects much more precious than power, a community that has survived ages of cold and drought, that has pioneered to flourish after devastations. This little but humongous utilitarian reserve is the biosphere. Born billions of years ago, this piece of Nature has never stopped to look young. It refreshes each day to sustain us all. Broadly speaking, our sole protector is our environment. It has been there since ages and will be there long after we have become a part of it. That is true. We have been brought forth through it and we replenish it after death. But what about the part in between? What do we do then? Let’s take a look at the balance we need to maintain for long lasting sustainable development on Earth. Human civilizations have grown around water as it forms one of the basic necessities of survival on Earth. It is through water that we communicate by building economies, sanctuaries for life, through use in daily activities, for transporting various products and services, making it of utmost value to us, humans. To harness the true potential of water resources, we constructed dams.
Introduction to Dams
Dams are structures that support and help cater to an unending use of water, most importantly flowing water of streams and rivers. Dams are built to store water in the form of a reservoir and then utilize the same to generate electricity or counteract cataclysmic events like floods and famines. The water reservoir, collected from the catchment area, behind the dam is called poundage. This is used for generation of electricity. The water, with a high enough potential energy, is allowed to pass through the penstock which is connected to a surge tank support, for use during low or high load conditions, and then reaches the turbine to start rotations and begin conversion of kinetic energy of water to mechanical energy. Spillways are also associated with the dam to act as routes for excess water in case of floods or heavy precipitation in the nearby watershed. This mechanical energy is then transferred to a generator station, where the same is converted to electrical energy. The head of the water, i.e. the height (pressure) of the dam from the turbine is important in determining the amount of potential energy stored in it and the generation of subsequent Megawatts of electricity from the same. The generator, in turn, is connected to a power grid and then to a power station for processing, amplification, transmission of electricity and finally to the consumers for utilization. There are two types of dams. One of those is a Surface dam, as mentioned above. The other one is called an underground dam. An example of such a dam is Fukuzato Underground Dam constructed in Miyakojima, Okinawa Prefecture, Japan. This type of a dam consists of a wall constructed to save underground water from pouring into the sea, such that it can be utilized for human consumption. Another important use of an underground dam is that maximum evaporation can be minimized due to its sub-surface location as it stores groundwater into its underground reservoir. Yet another important term to understand is a barrage. This construction is different from a dam in a way that in a barrage, no upstream reservoir is built, as only a few feet of water is elevated to divert its flow. While in case of a dam, the water is diverted as well as stored upstream.
Benefits of Hydroelectric Power Plants
Scientifically speaking, a dam has a number of benefits, both economical as well as structural. Some of those are:
- It acts as a water reservoir or storage for a given area and can be utilized in times of famines, droughts as well as floods.
- Electricity generation is also one of the major achievements of a hydroelectric power project, hence the name.
- It generates employment opportunities for a number of working classes, from engineers to architects and environmentalists to laborers.
- It forms the backbone of development in a country, helping provide electricity and water resources to diverse industries.
- It acts as a tourist resort and helps initiate funds for developmental purposes.
- Aquaculture and water intrinsic sporting activities can be conducted in the water reservoir of a dam.
Ecological Impacts of Dams
Considering these aspects, it is hard to believe that dams could ever pose a threat to our ecosystem. Sadly, it is true. Being megaprojects, with completion covering a time scale of 8-10 years, and inheriting a vast landscape for construction, dams come with their share of disadvantages. The main problems associated with these hydroelectric projects are:
- Ecological destruction: Dams are constructed over more than 50 hectares of land area, depending on the availability of generous watersheds and catchment area, accessibility to nearby roads, with a proper downstream gradient in the topography and surplus flow of water. These conditions, when met, lead to the suitability of dam construction. But in doing so, forests and associated habitats are to be removed and their proliferation curbed. Hence, the aquatic and the terrestrial ecosystems receive a huge blow, resulting in endangerment or even extinction of species.
- Human displacement: Villages and inhabited areas near and downstream need to be evacuated and settlements provided. Not only do the people dislocated need houses but jobs, services, agricultural land and proper education need to be in provision. This is a huge drawback for a nation like India, where basic amenities to a large population are in lack.
- Sedimentation: Another major setback to a dam is sedimentation. The disposition of sand, silt, clay, pebbles, organic matter and other particles over a period of time at the reservoir bed leads to a reduction in depth of the impoundment and results in a decrease in dam efficiency. Not only this but the erosion of banks around the dam area, which is now prone to soil erosion by wind or water, also leads to earthfall around it. Thus, threatening both the project and the people working on it.
An Environmental lawyer, Ritwick Dutta, who filed a case against Vedanta, representing the Dongria Kondh tribals of south-west Odisha, seeking a ban on bauxite mining in the Niyamgiri Hills, deliberated on Acts passed by the Parliament and how the NGT Act is being suppressed by MoEFCC, whose credibility and questioning of decisions forms a part and parcel role of the former. He also goes on to explain how renaming ministries (Ministry of Water Resources, Water Development, and Ganga Rejuvenation is hinted at here!) has created a caste system even between rivers, with Ganga receiving the top hierarchy position and the rest being treated as resources and not as separate river systems. Mr. Dutta explains how India has long reached excess electricity production but falls behind in accessing it. The country has had enough of power projects with vast generations of hydroelectricity but the problem lies in a transmission of the same to people living beyond the project horizon. Bad management, distribution failure, transmission losses and inefficient plants contribute to people still blabbing about power shortage and gagging environmental laws and ecosystems to death.
Disasters due to dam failure
Dams are creations of human beings, hence prone to failures and shortcomings. A few examples of such inefficiencies have been discussed which point to the fact that technologies should not always be trusted as these are as vulnerable to damage as us humans.
The Bento Rodrigues dam disaster, which occurred on November 5, 2015, in Bento Rodrigues, a subdistrict of Mariana, Brazil, due to a catstrophic failure of an iron ore tailings dam, led to the death of 17 people with 16 injured and massive flooding downstream. A technical report of Joaquim Pimenta de Avila, regarded as the foremost tailing dam engineers in Brazil, from September 2014 lists several structural damages on the dam, the main being construction of a buttress. Nearly 60 million cubic meters of iron waste poured into the Doce river, with toxic brown mudflows reaching the Atlantic Ocean 17 days later. Heavy metal traces of Arsenic, Lead and Mercury were found in greater than acceptable concentrations in the Rio Doce due to which water intake from this river was stopped. This event has been described as the worst environmental disaster in Brazil’s history, with harmful consequences of the contaminant to the rivers, its beaches near the mouth, banks and wildlife still unclear. Speculations regarding the collapse of the dam have been provided, with a 2013 report from Brazilian authorities claiming weakness in its structure but BHP Billiton, one of the dam venture groups, denies this version.
In India, Gateshwar Panth Canal Project in Bihar, a ₨ 389.31 crore project, faced a serious situation a day before its inauguration on September 20, 2017. The dam broke because of a release of water at full capacity during its trial run, causing waterlogging and water entering low lying parts of the area but no loss of life or injuries was reported.
In the USA, Lawn Lake Dam collapsed on July 15, 1982, resulting in flash floods killing 3 people camping in the area, in an event known as ‘The flood of 1982’. The sudden release of 30 million cubic foot of water caused a damage of $ 31 million to the town of Estes Park, Colorado and other downstream areas. The Colorado State Engineer determined that the reason of failure was deterioration of lead caulking on the joint between the outlet pipe and the gate valve leading to internal erosion of this earth-filled dam. Because of the dam’s remote and difficult location, repairs had been tough and inspections had lapsed. As a consequence of the dam’s failure and massive damage, aging dams at Pear Reservoir, Bluebird Lake and Sandbeach Lake in the Horseshoe Park, also the downstream catchment of Lawn Lake Dam, were demolished and removed.
These are some of the many small or large-scale disasters that have happened all over the world due to either human negligence in construction or in repair and maintenance.
Are there any alternatives to dams?
Alternatives to surface dams can be sub-surface or underground dams as mentioned earlier. Japan has been at the forefront in the construction of such dams, for human and agriculture consumption. India, with its tropical climate and high evaporation rates, must take a stride in building dams that are not subservient to excessive dehydration and drying, taking examples from Japan. An easy way out, though, is allowing free flow of water in rivers as at times building barricades in river systems reduce their capability to provide sustainable resources, both in terms of economic benefits as well as the capacity to restore balance in our ecosystem (Read more here).
Adeela Hameed: Miss Adeela’s hometown is Srinagar, Kashmir and she is currently pursuing Masters in Environmental Science from Amity University Noida.