Case Studies

CANADA

Québec is the number one producer of hydroelectricity in Canada. It also boasts one of the largest hydroelectric plants in the world, the Complexe La Grande near Baie James in the North of Québec. Hydro power represents 93% of the electricity sold and 97% of the energy produced in Québec.

This abundant and inexpensive energy source is safe for the atmosphere and gives Québec a distinct competitive edge in the North American energy market. Among other things, it constitutes a draw for companies in the electrochemical and electrometallurgical sectors.

James Bay Project

The James Bay Project, located in the Canadian province of Quebec, is testimony to the engineering skills of Hydro Quebec. Taken up in 1972, the phase I of the project consisting of three generating stations added more than 10000 MW of installed capacity to Quebec's power grid by 1985. The second phase of the project, which involves construction of six more generating stations, is to add another 5000 MW of capacity. Of this, four have already been commissioned. (The fifth, Laforge-2 is scheduled to be completed next year while the sixth, Eastmain 1, is on hold.) The La Grande 2 generating station, completed under phase I, is one of the World's largest power stations in terms of installed capacity (5328 MW).

The project makes use of the 548-metre drop between the source and mouth of the La Grande River and the average flow of 1700 cubic metres per second. The flow was doubled by diverting the waters of two adjacent rivers, Eastmain and Opinaca, into La Grande.

INDIA

Idukki Project

The Idukki hydroelectric project is located on the Western Ghats of the Indian Peninsula at an altitude of 695 metres above the sea level. The reservoir is formed by three dams-- an arch dam across the Periyar River and a concrete dam across the Cheruthony River and a masonry dam at Kulamavu, upstream of Idukki. The reservoir covers nearly 60 square kilometres and has a catchment of 649 square km. Water from the reservoir is taken down to the underground powerhouse at Moolamattom through an underground tunnel, yielding an average gross head of 2182 feet (665 metres). The project has an installed capacity of 780 MW with firm power potential of 230 MW at 100 per cent load factor.

The project involved diversion of the waters of upper part of Periyar into the Muvattupuzha River.

Effects

1. Severe drought in areas down stream of the river in summer and reduced fresh water availability for industries located near the mouth of the river due to diversion of water.
   
   
2. Hundreds of tremours had been recorded in the Idukki area after the impounding of the dam and most of them are classified as reservoir induced. So far, these tremours have not caused any serious damage
   
   
3. Valley slumpings and slope failures became common in the area following construction of the dam due to destruction of the forests during and after the construction. The project opened up the inner forests of Idukki district. This accelerated migration to the area, with the work force of around 6000 itself acting as the nucleus.
   
   
4. Submerged about 6475 hectares of evergreen and deciduous tropical forests.
   
   
5. Construction of roads, cutting of trees and encroachments led to loss of about 2700 hectares of forests and degradation of the remaining forests. Much of the degradation of forests that has happened over the years is irreversible. During the first phase of the Idukki project, dense vegetation cover in the surrounding areas went down by 56 per cent and sparse vegetation cover by 37 per cent. The area under agriculture increased by 126 per cent. (extent of encroachments that had taken place over the years).
   
   
6. Owing to loss of habitat, some reptilian species like the rare terrapin has become extinct or sparse. The reservoir attracted some species of birds, but the number of some other species went down.
   

References:
Comparative Study of Hydroelectric Projects in Canada and India: http://expert-eyes.org/canada.html

Hydroelectricity and the environment

This post will provide an overview on the general impacts that hydroelectricity has on the environment, narrowing the scope also to a case study on Canada, and how Canada is coping with the environmental effects.

Greenhouse Gases

Even though a hydroelectric plant produces no greenhouse gases, they can have an impact on the greenhouse effect. When a reservoir is filled and vegetation is submerged, methane and carbon dioxide can be produced as the vegetation decomposes. It has been proposed that as the size of the lake associated with the flooding due to a hydroelectric scheme increases, so does the amount of CO2 equivalent emissions. In fact, The Canadian Hydropower Association estimates that hydropower in Canada generates about 15,000 tonnes or less of carbon-dioxide equivalent for each gigawatt-hour of electricity produced. The amount of the carbon (contained in biological material) that is converted to methane increases with the size of the lake. However, this decreases as the output of the hydro-scheme and its lifetime increases. Over a period of a hundred years, methane has a warming effect twenty-one times that of CO2.

Although greenhouse gas emissions from reservoirs are small compared with emissions from other energy sources, studies are being conducted to better understand the source of emissions and to identify solutions. One option being used is clearing vegetation before an area is flooded.

Water

Some hydro facilities divert or store water to produce electricity, later discharging it back to the watershed. Although water is returned to its natural setting, this “in-stream” use of water has environmental impacts. Reservoirs can significantly change river use and habitat downstream. For example, they can:

• change water flow rates
• block fish migration
• disturb fish habitat
• expose riverbeds to erosion

Not all impacts, however, are negative. Reservoirs, for example, provide habitat for lake fish and nesting and feeding areas for migratory birds and waterfowl. In addition, they are used for recreation.

Fish and aquatic habitat
The need to protect fish and aquatic habitat is increasingly important. In inland regions of Canada, conserving local fish and their habitat is also becoming an issue, as a wide range of human activities put stress on regional ecosystems, including rivers and streams. In the case of hydroelectric generation, some fish species and aquatic habitats can be adversely affected through the creation of barriers and the modification of water flows.

Hydro operations affect fish and river ecosystems in different ways:

• dams can block salmon and other migratory fish species from reaching upstream spawning and rearing grounds.
• fish can be injured if they are drawn through water intakes or turbines.
• dams raise and lower water levels to meet changing electricity demand, causing fluctuations that are different from those naturally occurring in rivers and lakes. This can have harmful consequences: Low flows can contribute to the loss of fish habitat, while high flows may prevent fish migration or spawning. Wetlands are also sensitive to fluctuations since they depend on seasonal water flows such as spring flooding to maintain their ecosystems.
• dams can change the temperature and chemical balance of rivers and streams. For example, when river flow slows due to a dam, colder, denser oxygen-depleted water sinks to the bottom. If the water released to produce electricity is from the lower levels, the oxygen-depleted water can change habitat downstream.

In some cases, dams provide positive benefits to fish. Because the water stays longer in reservoirs, it becomes rich in zooplankton produced by decomposing organic matter. Slower-moving waters also attract fish such as trout that thrive in lake environments. Reservoirs can provide minimum flows in rivers, even in dry summers.

Hydro-operators in the Canadian Centre of Energy use a set of internal operating and reporting rules (called an environmental management system) to reduce their daily impacts on fish and their habitat. They also identify and monitor their impacts on fish throughout their hydro systems, and work to identify solutions. Hydro plants have facilities that direct fish around, over or through the dam. Examples include fish ladders (a series of pools arranged like steps that allow fish to pass upstream over a dam), fishways (channels that take fish over the dam) and screens that guide fish away from turbines, spillways and canals. Fish ladders help salmon and other migratory fish to swim upstream around dams to reach their spawning grounds. Hydro operators protect fish spawning habitats from disruptions by adjusting the timing and volume of water discharges from hydro facilities.

Slower-moving water in reservoirs can trap nutrients important to fish survival downstream. In these cases, hydro operators sometimes use fertilization programs to maintain food production and sustain healthy fish populations. Companies adopt new practices that improve hydro operations while reducing environmental impacts. One example involves replacing conventional greasing mechanisms at hydro stations to prevent the discharge of grease into the environment. Where dams affect river flows and fish habitat, industry invests in projects to restore or enhance the aquatic environment — for example, stocking streams and lakes with fish, rebuilding fish spawning areas and planting trees and grasses along shorelines.

The industry funds research activities by governments and conservation organizations that increase our knowledge about local fish species and the impacts of hydro operations on the aquatic environment. The topics of these studies are wide-ranging — everything from fish productivity to mercury levels in fish to turbine designs that are safer for fish to programs to restore healthy river ecosystems. The industry works closely with governments to create strategies and policies that protect fish and aquatic habitat. In 2002, for example, the Canadian Electricity Association entered an agreement with the Canadian Department of Fisheries and Oceans to work in partnership on initiatives to better protect fish and fish habitat resources associated with electricity generation in Canada.

Mercury
Mercury is a toxic element that enters the environment from natural processes (such as volcanic eruptions, vapor from oceans and the weathering of soils and rocks) and industrial activities (such as metal smelting, waste incineration, coal-fueled power plants).

Higher than normal levels of mercury can be found in fish inhabiting newly created hydro reservoirs. This mercury has a dual origin: part of it is released when soils and rocks, which naturally contain mercury, are flooded; the other part originates from the flooding of topsoil where mercury has accumulated from atmospheric emissions from industrial activities.
The creation of reservoirs frees the mercury trapped in soils and rocks. Bacteria then transform this relatively inert toxic mercury into a biologically more active form (methyl mercury), which penetrates the food chain and especially accumulates in the fatty tissue of predatory fish (such as northern pike, walleye, lake trout).

Well-established monitoring and mitigation procedures are in place to avoid health risks from mercury accumulation. Utilities and governments have carried out extensive research on mercury for many years. Recent studies have included monitoring of mercury content in fish in reservoirs, the impact of river flows on fish mercury levels and research on mitigation measures to reduce the mercury content of fish in new reservoirs. Industry and government studies suggest that the effect of flooding vegetation on mercury levels gradually decreases over time, with mercury levels returning to values similar to those measured in fish in surrounding natural lakes. This occurs after 10 to 30 years, depending on the fish species.

Land

Some of the most visible impacts of building and operating hydro projects affect the land. During construction, trees are cleared and roads are built. This can increase human access and hunting in fragile wildlife habitat areas.

If dams are constructed, there is generally a loss of forests and wildlife habitat. The land area disturbed or covered varies, depending on the type and size of the project.
One of the largest hydro systems ever built in Canada was the first phase of the James Bay Project in Quebec. Requiring major diversions of water, the project’s reservoirs cover an area equivalent to three times the size of Prince Edward Island. The project affected some 10,000 Aboriginal people.

Industry strives to manage these impacts through careful planning and operation of their facilities. Working with regulators, hydro developers assess new projects for potential environmental impacts, including local land use and wildlife areas, and identify different options. They also consult with local communities to identify ways to protect the environment, ensure access to hunting, fishing and trapping and preserve important cultural and recreational resources.

After completion, companies follow up by monitoring their projects to assess environmental impacts, including changes to wildlife and their habitat. If impacts cannot be avoided, they sometimes restore disturbed lands by planting trees and vegetation.

Biodiversity

With construction and operation of hydro facilities come changes to the different birds, animals, fish and plants populating an area. Dams can reduce biodiversity by making spawning habitat inaccessible to some fish species. Nesting, forage and cover along rivers and streams can be temporarily or permanently lost. Large reservoirs can block the traditional migration of animals along or across rivers.

These changes result in unsuitable habitat for some species. But in some cases, hydro plants and reservoirs can help wildlife habitat, supporting fish populations, especially those attracted to slower-moving waters, and providing resting and feeding points for geese and other migratory birds and waterfowl. Reservoirs can increase the shoreline of an original lake or river, expanding wildlife habitat for some animal species. Industry studies show that animals such as caribou seek out reservoirs in northern Quebec for feeding on banks and islands in the winter months.

In the initial years of their development, projects modify wildlife habitat. Hydro companies strive to reduce these impacts by careful planning and operation of facilities. For example, in Quebec, some hydro dams have been built on river sites not accessible to migratory fish.
The industry also implements measures to enhance wildlife habitat, including

• providing fish ladders
• rebuilding fish spawning habitat
• stocking streams and lakes with fish
• planting trees and grasses along shorelines
• creating wildlife preserves near reservoirs

To better understand industry’s impact on wildlife and their habitat, hydro companies fund wildlife research projects by government and conservation organizations.

Advantages and Disadvantages

Advantages:

• Hydroelectricity is a renewable energy source.


• Operation and maintenance costs for hydroelectricity plants are much lower than for thermal electricity power plants. Breakdowns are few because their mechanical design is relatively simple, and no excess heat is generated during operations.


• Hydroelectricity generating plants have a long life.


• When a hydroelectricity water storage dam is built, the water in the dam can be used as a source of drinking water and for recreational purposes such as boating and fishing.


• To meet any changes in demand for electricity, hydroelectricity generators can be stopped and started in minutes. A fossil fuel power station can take up to eight hours to shut down or restart and a nuclear power station can take up to several days.


• Although dams prevent the natural flushing out of a river during a flood, they also control flooding downstream in times of high rainfall and snowmelt.


• Hydroelectricity is one of the most efficient energy sources because most of the kinetic energy of the water is converted to electrical energy.


• No greenhouse gases or other dangerous gases are produced by the hydroplant.
  

Disadvantages:

• Usually a large area of land has to be flooded to ensure a continuous flow of water to the turbine. In some cases when a dam is built, large populations have to be relocated. In China, the Three Gorges Dam Project on the Yangtze River will displace more than 1 million people. (Reference: http://ipsnews.net/news.asp?idnews=39621)
  
• Dams affect river ecosystems. Rivers usually experience seasonal flooding that flush out river backwaters and deposit silt on riverbanks. Dams prevent those seasonal floods and allow silt and vegetation to clog up river backwaters. This causes changes to the environments, which may impact plant and animal habitats.


• Hydroelectricity dams are costly to build (though less costly then other power plants)


• An adequate supply of water from rain or snow is required for hydroelectricity plants to continue operation. If a drought occurs, electricity production can be severely affected. Countries that produce hydroelectricity need alternative electricity supplies for such events.

Electricity Generation

Potential energy -> kinetic energy -> hydroelectricity -> mechanical electricity -> electrical energy

//Energy Conversion

The water at the top of the dam contains a large amount of potential energy, providing the opportunity for electricity to be generated. The water flows from the reservoir to the dam and then to the power plant through a large pipe or tube. Water pressure, from the weight of the water and gravity, forces the water through the penstock and onto the blades of a turbine. The moving water then pushes the blades and spins the turbine. The turbine is connected to an electrical generator inside the powerhouse. The generator produces electricity that travels over long-distance power lines to homes and businesses. This entire process is called hydroelectricity.

Hydroelectricity is generated in large power generating stations using the same basic principle as a small grist mill, but on a much larger and improved scale for better efficiency. Electrical generators are attached to massive turbine devices which spin at great speeds as a result of water rushing through them. These massive turbines are extremely efficient at extracting the kinetic energy from moving water and converting that energy into power through these generators. It is the turbine and generator working in combination that converts mechanical energy into electric energy.

//Conditions for electricity generation

However, in order to generate electricity from the kinetic energy in moving water, the water has to be moving with sufficient speed and volume to turn a generator. Roughly speaking, one gallon of water per second falling one hundred feet can generate one kilowatt of electrical power. The water that used in this process is a renewable energy resource, just like the wind that turns the turbine attached to a generator.

The hydroelectricity extracted from water not only depends on the volume and speed, but also on the difference in height between the source and the water’s outflow. This height difference is called the head. The amount of potential energy in water is directly proportional to the head. Therefore, it is advantageous to build power dams as high as possible to convert the maximum energy from mechanical energy.

//Types of Hydroelectricity Generation

Hydroelectric generation can work without dams, in a process known as diversion, or run-of-the-river. Portions of water from fast-flowing rivers, often at or near waterfalls, can be diverted through a penstock to a turbine set in the river or off to the side. An example of diversion hydropower is the generating stations at Niagara Falls. Another run-of-the-river design uses a traditional water wheel on a floating platform to capture the kinetic force of the moving river. While this approach is inexpensive and easy to implement, it doesn't produce much power. For example, if the entire Amazon River is harnessed this way, it would only produce 650 MW of power.

Another type of hydropower, though not a true energy source, is pumped storage. In a pumped storage plant, water is pumped from a lower reservoir to a higher reservoir during off-peak times, using electricity generated from other types of energy sources. When the power is needed, it is released back into the lower reservoir through turbines. Some power will be lost, but pumped storage systems can be up to 80 percent efficient. There is currently more than 90 GW of pumped storage capacity worldwide, with about one-quarter of that in the United States. Future increases in pumped storage capacity could result from the integration of hydropower and wind power technologies. Researchers believe that hydropower may be able to act as a battery for wind power by storing water during high wind periods.