Essay on Hydro-Electric Power | Electricity | Economic Geography

Here is a compilation of essays on ‘Hydro-Electric Power’ for class 8, 9, 10, 11 and 12. Find paragraphs, long and short essays on ‘Hydro-Electric Power’ especially written for school and college students.

Essay on Hydro-Electric Power:

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Essay Contents:

1. Essay on the Introduction to Hydro-Electric Power
2. Essay on the Generation of Hydro-Electric Power
3. Essay on the Development of Hydro-Electric Power
4. Essay on the World Distribution of Hydro-Electric Power
5. Essay on the Sources of Hydro-Electric Power

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Essay # 1. Introduction to Hydro-Electric Power:

Electricity is generated in two main ways; by running water which derives hydro-turbines to generate hydro-electric power (H.E.P.), and by burning other fuels such as coal or oil to drive turbines to produce thermal power. Once generated the electricity derived from these two sources is exactly the same.

In terms of world electricity consumption, thermal power is far more important than H.E.P., and supplies about three-quarters of the world’s electricity. H.E.P., generation has some advantages over thermal power generation but at the present time, despite the rising costs of generating thermal electricity, new thermal plants and nuclear generators are more popular than H.E.P. schemes.

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Essay # 2. Generation of Hydro-Electric Power:

Despite its relatively minor role in satisfying world demands, H.E.P. is often more interesting to geog­raphers than thermal power. There are two reasons for this apparent anomaly. Firstly, whereas thermal electricity generation is really only an extension of the coal, oil and gas industries, the generation of H.E.P. depends on an independent energy source.

Secondly, H.E.P. schemes are often spectacular, in­volving the construction of large dams and other installations, often in remote areas, and at the same time the water stored to generate power may also have other far-reaching geographical effects such as improving river navigation, providing the means of irrigation and preventing floods. Imaginative multi­purpose schemes of this kind give great prominence to H.E.P. generation, while thermal electricity gener­ation seems relatively mundane.

Water Power:

Running water from streams, rivers and melting glaciers has long been utilized by men as a motive power for grinding flour or sawing logs. Primitive water-wheels have been placed in swift-flowing streams, at rapids or waterfalls, to generate power since the earliest times.

Such sites were the earliest industrial locations, des­pite the fact that they are often in relatively remote and sparsely populated mountain areas. An improve­ment was the damming and channeling of streams to provide a sufficient head of water even in rivers of rather shallow gradient to drive water wheels. The great disadvantage of water-power was the fact that it could not be used at a distance but only directly by siting a mill or small factory at the river side.

Three important inventions, however, have allowed water power to be used to generate electricity and thus enhanced the importance of this source of power which had previously been over-shadowed by the use of mineral fuels.

1. The development of the hydro-turbine, a very efficient type of water wheel, which rotates very rapidly when a jet of water is directed against it, so that H.E.P. can be generated.

2. The invention of the dynamo, which converts the energy of the rapidly turning turbine into electri­city.

3. The development of cement, which allows large dams to be constructed, capable of holding back vast reservoirs.

Thus the head of water and the amount of energy released by its passage through the dam is much greater than in the small earth or stone works of the past and the greater the pressure the more power can be obtained. The main stages in the generation and transmission of H.E.P. are shown in Fig. 13.1.

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Essay # 3. Development of Hydro-Electric Power:

1. A Head of Water:

The hydro-turbines are driven by the force of the water against their blades. In natural streams and rivers the force of the water is greatest where it flows most swiftly or where it falls rapidly as in the case of a waterfall or rapids. Even a small stream, when dropping from a great height has tremendous power and can be used to generate electricity.

Thus many H.E.P. generating plants are located in mountainous districts where the rivers and streams have a steep gradient and waterfalls are common, e.g. the Swiss Alps, Scan­dinavia, the Rocky Mountains, Appalachians and the Japanese Alps. These areas, most of which have been glaciated, have an abundance of hanging valleys and turbulent mountain streams.

Waterfalls also occur at scarps and plateau edges, e.g. Niagara Falls, Victoria Falls, and these, too, are ideal sites for H.E.P. generation. Many countries possess a Fall Line at which mountain streams drop down to a coastal plain, e.g. along the eastern side of the Appalachians, or along the eastern border of the Scandinavian Mountains in Sweden.

Waterfalls are not essential to provide a suffi­cient head of water. Rivers with a low gradient but a large volume of water can also be utilized, e.g. the River Shannon in Ireland or the Volta River in Ghana.

The most reliable way of obtaining a sufficient head of water either in upland or lowland areas is by building a dam. By storing up the water in a reservoir, the water which is allowed through the penstocks is under great pressure and is thus ideal for generating H.E.P.

2. Large Volume of Water:

Generally speaking, although almost any river could be used to generate H.E.P., in practice it is much more economic to harness large rivers such as the Indus, Nile or Zaire, than to use smaller rivers and streams. Use of such small streams would produce only limited supplies of power and would entail building a multiplicity of small H.E.P. stations. The har­nessing of large rivers, though more costly and difficult, gives far better returns.

3. Regular and Reliable Water Sup­ply:

It is important that rivers to be harnessed for power generation should not be subject to great fluctuations in the volume of water, since this would make it difficult for plants to operate at a constant level of power production. A regular flow of water allows the generating plant to main­tain a steady output of power for use by homes and factories throughout the year.

Long droughts in the monsoon, savanna and Mediterranean lands may reduce the volume of rivers. Similarly when rivers freeze in winter in the cool temperate lati­tudes the water is locked up as ice and river flow is reduced. When planning the exploitation of rivers for H.E.P. generation, the fluctuations in flow, must be taken into consideration. Even then unex­pected droughts may reduce flow and thus reduce power output.

For example, a prolonged drought in North and South Carolina, U.S.A., during 1911 reduced power supplies so that 152 cotton mills were forced to stop work and 7,000 men were laid off. Fortunately such problems do not often arise today since climatic events in different parts of the country may be different and the use of a national grid allows electricity supplies to be obtained from alternative sources.

However, it is still true to say that the most favoured areas for H.E.P. generation are those where rainfall is well-distributed around the year, e.g. North-West Europe, the equatorial tropics, since rivers in such areas are least affected by seasonal fluctuations.

The construction of dams which store water and control its release at a regular rate is obviously preferable to reliance on river flow which may fluctuate, but a dam is no security in the face of prolonged drought. The reservoir may dry up as well as the river, and power generation cannot re­start until a sufficient head of water has again been built up.

On the other hand by storing water in the rainy season for release during the dry months, e.g. in monsoon regions, dams are of great importance in regulating river flow, with resultant advantages both for power generation and other purposes such as irrigation.

4. Presence of Lakes:

The presence of natural lakes along the course of a river is often a great advantage in H.E.P. development, especially in areas with a seasonal rainfall distribution. They help to store flood-waters and regulate river flow naturally and render the construction of dams either unnecessary or at least easier.

In glaciated areas existing corrie and ribbon lakes are often used as reservoirs, their outflow being used for H.E.P. generation. There are many examples of this in Switzerland and Britain. In most cases, however, there are few natural lakes in suitable locations and dams are built to create large artificial lakes.

The Hoover Dam, which holds back more than 38,290 million cu. metres (31 million acre ft) of water in Lake Mead was for many years the largest, but in recent years many new dams have created far larger lakes. Some of the largest are in Africa: Lake Kariba contains 160,000 million cu. metres (130 million acre ft) of water; the Aswan Dam holds back 156,900 million cu. metres (127 million acre ft) and the Akosombo Dam in Ghana stores 148,200 million cu. metres (120 million acre ft) of water. There are also huge dams in Asiatic U.S.S.R. at Bratsk and Krasnoyarsk.

5. Space for a Reservoir:

Another aspect of planning the construction of a dam for H.E.P. generation is that there must be a suitable location for creating a lake if this is necessary. For instance, the valley behind the dam must be deep enough to hold a sufficient supply of water to provide a good head. At the same time a dam cannot be built which would flood valuable farmland or a densely- settled area without careful calculation of the rel­ative human and economic advantages and disad­vantages.

In many densely peopled countries the most suitable sites for dams and reservoirs are in the more remote, sparsely-settled mountain areas. Such locations cannot be used if they are too distant from markets. Gorges have many advantages for reservoir creation. They require relatively nar­row dams and the area flooded is usually restricted, but, because the gorge is deep, a large capacity is ensured. Gorges, too, are rarely of agricultural im­portance because of steep slopes.

6. A Large Market:

As electricity cannot be stored for long on a large scale, the demand for the power generated, by both domestic and industrial consumers, must be large and constant to warrant the initiation of H.E.P. stations. Surveys have to be conducted to assess the extent of the market, the possible growth or decline of the region in rela­tion to future regional and industrial development.

The availability of alternative fuel supplies must also be taken into consideration; the demand for electricity in Japan, Canada, Switzerland, Norway and Sweden, especially for the development of metallurgical industries, is partly due to the general lack of coal or oil.

The need for an already existing market is most vital to schemes only for H.E.P. generation. In multi-purpose schemes H.E.P. is often a minor fac­tor. However, large multi-purpose dams built main­ly to foster agriculture, may form the basis of in­dustrial development. H.E.P. supplies from multi­purpose schemes may thus begin by being relatively unimportant but increase in output as time goes on.

7. Heavy Capital Outlay:

Modern large- scale H.E.P. projects are expensive undertakings in­volving dam erection, power plant construction, costs of transmission and round-the-year main­tenance as well as incidental costs of compensation, etc., to people affected by the scheme.

The deliv­ery of the power supply from the point of genera­tion to consumers, sometimes hundreds of kilo­metres away, involves the construction and serv­icing of pylons, high-tension cables, even undersea cables in some cases, and transmission lines often cross very difficult terrain.

Permission has to be sought from the owners and authorities concerned when the transmission lines are laid across private ground, and rental paid for the land used. A team of engineers, wiremen and administrative staff has to be maintained to run the entire operation. Thus not only initial costs, but also maintenance costs are very high.

It is a common misconception, because H.E.P. is derived from water which is free, that it is always cheap. Once initial costs have been recouped it may indeed be relatively cheap but this will necessarily take some time. A

t first, however, installation costs are usually much higher than for thermal plants. Because initial costs are so high H.E.P. undertakings are usually financed and operated by governments, which are concern­ed more with providing services than with profits. This is particularly true of multi-purpose projects.

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Essay # 4. World Distribution of Hydro-Electric Power:

In the light of the conditions favouring H.E.P. development, it is clear that certain parts of the world are better suited by relief, climate or other factors to the exploitation of water power (Fig. 13.2).

Generally speaking H.E.P. stations are found in the following areas:

1. Mountainous districts, especially those which have been glaciated and have many waterfalls and lakes.

2. Tropical and temperate areas with a moderate to heavy well-distributed rainfall.

3. On major rivers with a large volume of water, whether flowing constantly or having seasonal fluc­tuations which can be minimized by creating reser­voirs.

4. In industrial countries where all power sources, including H.E.P., tend to be well-developed because of the large market.

5. In areas where regional development is pro­moted by the construction of multi-purpose dams.

H.E.P. potential is not equally distributed around the world. Some countries, e.g. the U.S.A., Switzer­land, have many more potential sites for H.E.P. stations than others, e.g. Britain, the Netherlands. However, even those countries with moderate poten­tial do not always develop H.E.P. if alternative sources of power are available.

In many countries of South America, Africa and in Asiatic U.S.S.R. many poten­tial H.E.P. sites are ignored because the small popula­tion does not provide an adequate market for the generated power. As much as 40 per cent of potential H.E.P. is in Africa and Asia, including Asiatic U.S.S.R., which has the next largest potential resources.

How­ever little H.E.P. has been developed in most of the African and Asian countries except for a few large schemes like the Volta, Kariba or Aswan in Africa and a number of large dams on the Indus tributaries in northern India and Pakistan. In South America Brazil, which has few other energy resources has been the primary developer of H.E.P. but its total output is not much greater than that of Norway, a fraction of its size.

The developed countries as a whole, North America, Europe and Japan, have about one-third of H.E.P. potential but have developed much of this so that they account for 80 per cent of developed H.E.P. The U.S.A. is the world’s leading producer of H.E.P. but so large are the U.S. power requirements that H.E.P. accounts for only about 10 per cent of electricity supplies.

In Canada H.E.P. is much more important, accounting for nearly three-quarters of electricity supplies. In Europe H.E.P. is most important in Scan­dinavia and countries bordering on the Alps—Swit­zerland, France and Italy. The U.S.S.R. has large plants in both European and Asiatic sectors of the country.

North America:

The United States of America and Canada together account for about a third of the world’s developed water power.

They are the greatest H.E.P. producing nations for the following reasons:

1. Natural H.E.P. sites are abundant:

Many are found at the Fall Line of the Appalachians, in the Rocky Mountains, in the Mississippi Basin, on the Laurentian Shield, along the Great Lakes—St.’ Law­rence waterway. Streams with steep gradients, rivers with a large volume of water, and man-made reservoirs are all utilized for H.E.P. production.

2. Technological development in hydraulic engi­neering is advanced:

The U.S.A. is a world leader in the science of dam construction and H.E.P. genera­tion, partly due to long experience in developing such resources, and partly to the high standard of tech­nology in the country. Many American and Canadian hydraulic engineers are sent abroad to the developing nations to assist them in the planning and construction of multi-purpose dams.

3. There is a large demand for H.E.P:

Large quan­tities of electricity are required by homes and factories. Much of this is supplied by coal or oil but for many industries water power is most important. These include the pulp and paper industry in Canada and U.S.A.; aluminium smelting and other electrolytic, metallurgical and chemical industries; and textiles, es­pecially in the U.S. South. Use of electricity from both water and other sources including geothermal and nuclear power is continually increasing.

4. There is government backing for large H.E.P. projects:

The American and Canadian governments have allocated large sums of money for multi-purpose schemes such as the T.V.A. and the St. Lawrence Seaway. In the T.V.A. region more than 25 dams were erected across the River Tennessee and its trib­utaries to control floods, irrigate land, improve inland navigation and generate H.E.P. for farms and industries.

On the St. Lawrence, deepening and canalizing of the river to provide access for large ships was assisted by dam construction and H.E.P. is also generated. Many other schemes have benefited from government finance.

It is important to bear in mind that, despite the importance of North America in world H.E.P. devel­opment, hydro-electricity accounts for only a relatively small proportion, about 10 per cent, of power supplies in the U.S.A. In recent years growing dependence on oil and, where alternative sources were required, con­centration on nuclear power development, have re­duced interest in expensive H.E.P. developments but there is still great untapped potential.

In the New England states water-power was utilized in textile mills and steel works much earlier than either coal or oil, though these fuels became much more important during the nineteenth century and H.E.P. development has taken place more recently. In the Pacific region and the Rocky Mountain states, where coal is scarce and oilfields are relatively inac­cessible, H.E.P. has become the chief source of power.

More than two-fifths of the U.S.A.’s hydro-electric power now comes from these western states, in which are located many well-known dams. The Grand Coulee Dam is one of many dams on the River Columbia in Washington (Fig. 13.3). It is 180 metres (600 ft) high and holds back 11,830 million cu. metres (3,130,000 million U.S. gallons) of water, is a multi-purpose dam and has played a vital role in the reclaiming of the arid lands of the West.

The Hoover or Boulder Dam on the River Colorado in Arizona is 222 metres (727 ft) high and holds back as much as 38,290 million cu. metres (10,000,000 million U.S. gallons) of water in Lake Mead. It supplies electricity to farms and factories within a 640-kilometre (400-mile) radius of the dam as well as supplying water to the industrial sites of California and irrigation water to the Imperial Valley. Of the 110 million kW of remaining untapped potential over half is in the West and one-sixth is in Washington state alone.

East of the Rockies the major H.E.P. stations of the U.S.A. are found in the north-east from Maine to Minnesota and in the southern Appalachians. They include plants at the Niagara Falls and the Hudson Rapids. The St. Lawrence Seaway with huge generat­ing plants at Beauharnois, Cornwall, Prescott, King­ston and Montreal, provides power needed for the in­dustrial centres of the Lake Peninsula and the Great Lakes—St.Lawrence region on both sides of the border.

Electricity is generated at the St. Anthony Falls at Minneapolis on the Mississippi River and has assisted the growth of many industries in the area such as flour-milling, meat-packing and fruit-canning. The Long Sault Rapids at Massena generate H.E.P. for aluminium smelting.

There are many dams along the Mississippi and Missouri Rivers including those at Fort Peck, Garrison, Fort Randall and Gavins Point which help flood control and also provide irrigation water for the croplands in the riverine districts.

There are many dams along the Tennessee River and its trib­utaries. East of the Appalachians rivers plunge down from the more resistant Piedmont Plateau to the Atlantic coastland giving rise to a string of Fall Line industrial sites with generating plants at or near such towns as Clark Hill, Hartwell, John Kerr and Conowingo.

In Canada H.E.P. constitutes about 70 per cent of the annual electricity output. The bulk of the devel­oped power is located in eastern Canada with dams along the St. Lawrence River and its tributaries, e.g. the Manicougan, Outardes, Peribonka, Saguenay and St. Maurice. Some major H.E.P. generating plants include those of the Niagara Falls and the St. Law­rence Seaway, serving the Canadian industrial cities of Toronto, Montreal, Hamilton, Kingston and Wind­sor.

Those at the Sault-Ste-Marie rapids at the outlet of Lake Superior support a thriving steel and lum­bering industry. The H.E.P. stations on the Nipigon River near Lake Nipigon supply power to Port Arthur and Fort William which handle large volumes of grain, oil and metallic ores from the Prairies and the Cana­dian Shield. Winnipeg is served by H.E.P. from the Winnipeg River.

On the Pacific coast, British Columbia is well-en­dowed with water-power. The Kitimat Scheme on River Nechako supplies electricity for saw-milling and for aluminium smelters that import bauxite from Jamaica, the Dominican Republic and Guyana. Other H.EP. stations are located at Vancouver, Bridge River, Kemano, Arrow Lakes and Duncan (Fig. 13.3).

Europe:

Europe ranks second in the output of H.E.P., most of its annual production coming from only six coun­tries: Italy, France, Norway, Sweden, West Germany and Switzerland.

But there are few large schemes comparable to those of North America for the follow­ing reasons:

1. The H.E.P. schemes are undertaken by small individual European countries, with nothing like the market potential or financial backing available in the U.S.A.

2. European industrial areas grew up and are still located near coalfields. Coal is still a major supplier of power and water-power does not play such an impor­tant role in many countries.

3. The relief of much of Europe is not rugged. Countries like Denmark, the Netherlands and Belgium are so flat that H.E.P. generation is almost impossible.

4. European rivers are generally short and the major rivers flow through several countries. Thus gigantic multi-purpose schemes are less feasible than in the U.S.A. or Canada. Moreover if large lakes were created they would flood densely-settled areas.

5. European projects are usually undertaken main­ly or solely for power generation, unlike the multi­purpose dams of America, such as those on the St. Lawrence, the Mississippi-Missouri, and the Tennessee. Because of their more limited use they are usually smaller and less spectacular.

Italy:

Lack of coal and oil in Italy has encouraged the Italians to develop much of their water-power potential. Almost half of Italy’s electricity output comes from H.E.P. The southern slopes of the Italian Alps are steep and have been glaciated. H.E.P. stations provide power for the industrial region of the Lombardy Plain in northern Italy, centred on the cities of Milan, Turin and Genoa. In peninsular Italy power is generated from the streams of the Apennines and serves domestic and industrial users in Rome, Naples, Ancona, Bari and other coastal areas. Italy produces 52,700 million kWh of H.E.P.

France:

France’s annual output of electricity is about 210 800 million kWh of which 37 per cent is derived from H.E.P. The power stations are located mainly in the rugged upland regions of the Pyrenees, the Central Massif and the French Alps. There are also several large dams on the Saone and Rhone Rivers, e.g. at Donzere-Mondragon.

In Brittany there is a tidal power scheme on the Rance estuary. The power stations at Grenoble on the Isere, and Argentiere on the Durance in the French Alps support electro-metal- lurgical and aluminium smelting industries.

Norway:

In terms of per capita output of water- power, Norway is the greatest in the world. Its per capita output is almost twice that of its neighbour, Sweden, and six times that of France. The reasons are not hard to find: rugged relief, glaciated uplands, heavy snowfall, moderate to heavy well-distributed precipitation, and, until oil and gas were found in the mid-1970s, a lack of fossil fuels.

Major H.E.P. stations include those of Sarpsborg in Oslo Fiord, which has associated calcium carbide and zinc concentration plants; Notodden, south of Oslo, where nitrate, ammonia, acids and artificial nitrogen are made; and Mo-i-Rana, with its steelworks. Norwegian industries, such as paper and pulp industries; fish-canning and preservation; the manufacture of carbide, nitrate of calcium, ferro-silicon; other ferro-alloy and metal­lurgical industries, depend very heavily on H.E.P. Of Norway’s annual electricity production of 72,520 million kWh, 99.7 per cent is hydro-electricity.

Sweden:

Sweden enjoys many advantages in H.E.P. development, as does Norway, except that in the north of the country heavy snow accumulation and river freezing due to the more continental climate leads to river fluctuations. Northern and central Sweden have a rugged relief and many swift-flowing streams that drain into the Gulf of Bothnia and the Baltic Sea.

There are plans for many plants in the north and several are already established, but most of the power stations are located on the south-eastern slopes of the Scandinavian Mountains. That of the Trollhattan Falls on the River Gota is the most important. Of Sweden’s annual electricity output of 90,000 million kWh, 60 per cent comes from H.E.P. Sweden has a small sur­plus of electricity which is exported to Denmark by a submarine cable.

Germany:

Despite East and West Germany’s small water-power potential, the resources have been well- developed to supply domestic and industrial electricity demands. Major H.E.P. stations are located at Grevenbroich (outside Dusseldorf), Innerwerk (mainly for aluminium smelting) and Bitterfeld in East Germany.

The North German Plain, though traversed by many rivers, is so low-lying that there are practically no H.E.P. plants, but there are many small plants in the Alpine region and Southern Uplands. In West Germany H.E.P. accounts for 5 per cent of total electricity supplies and coal and imported oil are the major in­dustrial fuels.

Switzerland:

Switzerland has, for its small size, a relatively large H.E.P. output. Of its annual electri­city production of some 46,000 million kWh about 79 per cent comes from H.E.P. Electricity accounts for nearly 30 per cent of total energy requirements. Industries such as clocks, watches, precision and opti­cal instruments, machinery, electrical appliances and chemicals, rely heavily on electricity. Swiss homes are lit and heated by electricity. The railways are also ex­clusively electrified. Switzerland’s main advantages for H.E.P. generation are its rugged, glaciated uplands and numerous falls, rapids and lakes.

U.S.S.R.:

The Soviet Union produces 1,150,000 mil­lion kWh of electricity of which 141,000 or 12 per cent is H.E.P. Current production comes mainly from the European part of the U.S.S.R. though several im­portant plants have been built in Siberia in recent years and 80 per cent of the potential H.E.P. lies in the Asiatic part.

Amongst the most outstanding pro­jects is the multi-purpose Dnieper Combine Scheme, comprising a series of dams along the Dnieper, in the Ukraine, which not only provides power for the in­dustries of south-west Russia, but irrigates large areas of semi-arid lands that are capable of growing wheat, sugar-beet, oats and barley. The dams have raised the water-level, making the Dnieper navigable by large steamers for over 800 km (500miles).

Similar schemes on the Volga and the Don have improved the navigability of the rivers to their outlets at the Black Sea and the Caspian Sea respectively. There are two huge dams on the River Volga at Volgograd and Kuybyshev. High-voltage transmission lines transmit the electricity to cities as far as Moscow (1,040 km or 650 miles away) and the Donbas. Other large power stations include those of Irkutsk, Bratsk, the largest single H.E.P. plant in the world, and Krasnoyarsk in Siberia; and Beloyarsk on the shores of the Caspian Sea.

Soviet H.E.P. development accounts for 12 per cent of total electricity and has been hampered by several difficulties. The vast size of the country, with its relatively sparse and dispersed population, means that it is difficult to establish an efficient and economic national grid. The fact that most of the major rivers flow north and are frozen for much of the year is an­other severe disadvantage as river regimes are very varied.

Despite these difficulties, a number of very large H.E.P. generating dams have been built in Siberia in the hope that the industries they serve will attract settlers to the empty east of the country. However, these dams have proved rather uneconomic for their output cannot easily be used outside their immediate area and they are thus still running at less than full capacity.

The gains in industry and settlement in Siberia have not yet offset the tremendous costs of building H.E.P. plants. In the U.S.S.R. hydro-electricity is thus a relatively expensive form of power. Thermal electricity, oil and natural gas are much more economical.

Asia:

Though Asia has great H.E.P. potential the conti­nent’s developed water-power resources are very small, amounting to only a quarter that of Europe.

Japan:

Only one Asian country, Japan, has developed its H.E.P. resources on a large scale. Lack of coal and oil, a rugged topography, well-distributed heavy pre­cipitation and an enormous industrial demand for power are some of the obvious factors that have led to Japan’s large H.E.P. output but Japan’s unstable geological situation with frequent earthquakes are a deterrent to the building of really large dams even if the mountain streams were large enough to warrant them. H.E.P. accounts for 14 per cent of the total electricity output.

There are ten large H.E.P. plants located on the slopes of the Japanese Alps and many smaller ones, though huge thermal plants situated in the industrial districts produce the bulk of the annual electricity output of 532 600 million kWh.

India and Pakistan:

India and Pakistan have developed many H.E.P. resources, especially in con­nection with huge multi-purpose schemes on the Indus and Ganges and smaller schemes on the short, swift streams of peninsular India. Some of the major multi­purpose schemes include the Sukkur Barrage, Guddu Barrage, Taunsa Barrage, Kotri Barrage, Mangla and Tarbela Dams and the Triple Canal Project of Punjab, Pakistan; the Sinsi Dam of the Middle Ganges and smaller dams on the Mahanadi, Godavari, Krishna and Cauvery.

The uneven distribution of rainfall in the Indian sub-continent, with long droughts and frequent floods make dam construction an essential feature of water management for flood control, water storage and irrigation. In India H.E.P. accounts for 37 per cent of total electricity.

China:

China has harnessed water-power potential for industrial requirements as well as for flood con­trol. Several large dams have been constructed along the Huang He (Hwang Ho) to hold back excess water during the rainy monsoon so that floods are minimized. Similar multi-purpose projects are being undertaken along the Chang Jiang (Yangtze Kiang), the Xi Jiang (Si Kiang) and in Manchuria, but China produces less electricity than France or Italy, and H.E.P. is only a minor contributor to total electricity supplies.

North Korea has several dams in the mountainous north built by the Japanese during their occupation of Korea from 1910 to 1945. The largest is the Shuifeng Dam across the Yalu River, completed in 1944. South-East Asia as a whole has tremendous H.E.P. potential but little is developed. Most H.E.P. schemes are small with power stations, designed only for local domestic use.

With increasing emphasis on industriali­zation, larger dams are being built such as the Abu Bakar Dam of the Cameron Highlands in Peninsular Malaysia. Many multi-purpose dams are proposed in the Mekong Scheme in Indo-China but little progress has yet been made (Fig. 13.4).

The Southern Continents:

In potential water-power resources, South America is comparable to the U.S.S.R., but developed capacity in many of the countries is small. The abundance of petroleum and the underdevelopment of most of the South American republics account for its low H.E.P. production.

Brazil leads in both potential and de­veloped water-power, with 60 per cent of South American output, coming mainly from the south-east though there is an important plant at Paulo-Alfonso on the Sao Francisco River in the north-east. Some 93 per cent of Brazil’s electricity is from H.E.P. Ar­gentina and Venezuela are significant H.E.P. producers.

In water-power potential Australasia is probably the least favoured region in the world. New Zealand has more favourable conditions but a smaller mar­ket than Australia for H.E.P. development because of its mountainous relief, abundant precipitation and the relative lack of mineral fuels.

The largest H.E.P. project in the region is located in south-eastern Aus­tralia, namely the multi-purpose Snowy River Scheme, which has doubled Australia’s H.E.P. output (Fig. 13.5). It also extends cropland by providing water for irrigation in areas of Australia where rainfall is both low and unreliable. Two other major dams are found at the Tully Falls, northern Queensland, and on the Shannon, Tasmania.

The continent of Africa has the least output of hydro-electricity but its potential is the greatest in the world. Much of Africa is a plateau dropping ab­ruptly to the coast or to the Rift Valley and furnishing natural ‘heads’ for H.E.P. generation. Many parts of Africa lie within the humid tropics where precipita­tion is heavy and well-distributed, but river fluctuation may be a problem in the savanna regions.

The lack of a large market for H.E.P. is the main hindrance to de­velopment. Some of the more important African H.E.P. plants include the Victoria Falls and Kariba Dam on the Zambesi, the Kafue Dam in Zambia, the Owen Falls in Uganda, the Cabora Bassa Dam in Mo­zambique, the Aswan Dam of Egypt, the Sennar Dam of Sudan and the Akosombo Dam on the Volta River in Ghana.

Since independence, many African countries have begun to develop multi-purpose schemes as a basis for national or regional industrial and agricultural development. Some of the multi­purpose dams in Africa hold back enormous man- made lakes but the small market means that, as yet, H.E.P. output is rather small.

13. B The Aswan High Dam which provides H.E.P. and store the Nile waters for irrigation, under construction Eric Kay.

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Essay # 5. Sources of Hydro-Electric Power:

Electricity can be obtained from a variety of sources other than conventional hydro or thermal generators. The most important of the present-day alternatives is nuclear power, which in many indus­trialized countries already provides as much or more energy than H.E.P. There are, however, many objec­tions on the grounds of pollution and operational dangers to nuclear power and its development has been much slower during the last twenty years than was envisaged when the U.S.A. and European coun­tries first began to exploit it.

The next most widely used of the ‘new’ sources of power today is geothermal energy, that is energy derived from hot springs, emissions of dry or wet steam and from hot rocks at depth. Geothermal energy is most used in Iceland where it supplies 15 per cent of total domestic demand, mostly for cen­tral heating, including domestic heating for the whole of the capital, Reykjavik.

Italy’s geothermal sources at Larderello are used to run a power station and in California nine power plants are fed by geothermal sources at The Geysers. Californian output is about half the world total. Japan, New Zealand, the Philip­pines, Turkey and the U.S.S.R. all have some interest in exploiting geothermal power from steam or hot water sources associated with volcanic areas, but in future the use of ‘hot rock’ at depth may be more important since such occurrences of heated rocks are fairly widespread.

The plan is to pump cold water down one borehole into the hot rock and extract the resultant steam through another borehole. Many countries including the U.S.A. and Britain hope to generate electricity from such rocks but the tech­nology for doing so is still in its infancy and much re­search remains to be done.

Thus in the foreseeable future geothermal energy is unlikely to become im­portant outside certain restricted areas, but there are plans to increase its use greatly in the U.S.A. There the demand for electricity is so great, and the opposi­tion to the pollution caused by conventional gene­rators is so widespread, that geothermal power may provide a major source of electricity in years to come. Geothermal energy has the advantages of being freely available, a flow resource, and of causing little or no pollution when electricity is generated from it.

Alternatives to conventional H.E.P. include tidal power, already successfully developed on the Rance Estuary in Brittany, France, but there are probably only seven or eight sites in the whole world where it could be developed and initial development costs are enormous.

More hopeful is the use of wave energy by floating plants which would use the constant motion of the waves to drive turbines, but these would be difficult to use in areas prone to storms where violent seas might destroy the power plant.

Another possible use of the seas is to make use of the heat gradient be­tween surface and deep-sea water (especially in the tropics) or between warm currents such as the Gulf Stream and adjacent colder water. Boilers operating in a vacuum could drive turbines given a difference of as little as 10°C (18° F). Another possibility is to release energy from the hydrogen in sea-water by nuclear fusion.

Wind power has been harnessed for centuries to drive mills and pumps but research into modern windmills has not proved very successful. Rotary arms are an inefficient producer of power and the wind is too variable in speed, direction and persis­tency for any real use to be made of it, though re­search is continuing on methods of using the wind to create a vacuum in a kind of silo, which would theoretically draw in air rapidly enough to power a turbine.

Solar energy is probably the most hopeful pros­pect for alternative power supplies and is already used on a small scale for domestic heating, but at present the technology for collecting the heat and storing the resultant energy is not sufficiently ad­vanced for large scale use to be economic.

If solar energy could be developed it would be of immense importance. It is estimated that the solar energy ‘falling’ on the U.S.A. in a year is 700 times the pre­sent total energy consumption of the country. It could also be a great boon to developing countries since many are in the tropics, receiving much sun­light. Two ways exist of using the sun’s rays.

First by using plates to collect and reflect the heat to power generators. The biggest problem with this is setting up the huge collectors that would be re­quired for large-scale use. One suggested answer is to collect solar energy by an artificial satellite and trans­mit it to the earth in the form of micro-waves.

Second, and more hopeful, is the use of photo voltaic cells composed of a semi-conducting material that converts light into electric current. This system is already used on a small scale for watches and it is thought that commercial use of the cells could be widespread by the late 1980s. Some estimates suggest that solar energy may meet about 7 per cent of the U.S. energy demands by the year 2000 and as much as 25 per cent by 2020. But the prospects for the cloudy northern countries of Europe are not so bright.