Dams,types of dams,working of dams,benefits of dams,costs of dam

introduction to dams w.r.to civil engineering

1. DAMS MUBARAK ALI L-18CE-11 3/26/2019 1

2. outin INTRODUCTION Dams in the 20-21 century Types of Dams How do dams work? benefits of dams? Dams and climate risk Costs of dams? 3/26/2019 2 OUTLINE:

3. DAMS *.The International Commission on Large Dams (ICOLD) defines a dam as ‘an artificial barrier that has the ability to impound water, wastewater, or any liquid-borne material, for the purpose of storage or control of water’. *.Dams are made from earth, stacked rock or concrete, and are usually constructed across rivers to store water in the reservoir that is formed behind the dam as a result of the river being blocked. 3/26/2019 3

4. Dams in the 20th century And Some Facts Today, around 3 800 km3 of fresh water is withdrawn annually from the world’s lakes, rivers and aquifers.2 This is twice the volume extracted 50 years ago. For thousands of years, dams have been used to store water and to create energy. However, 90 percent of global dam investments have been made after (1949-1950, both in terms of the millions of small or medium sized dams and the thousands of dams higher than 50m The last century saw a rapid increase in large dam building. By 1949 about 5 000 large dams had been constructed worldwide, three-quarters of them in industrialized countries. By the end of the 20th century, there were over 45 000 large dams in over 140 countries. As dam building accelerated after the 1950’s, opposition to dams became more widespread, vocal and organize 3/26/2019 4

5. Dams in the 20th century And Some Facts The top five dam-building countries account for nearly 80% of all large dams worldwide. China alone has built around 22 000 large dams, or close to half the world’s total number. Before 1949 it had only 22 large dams. Other countries among the top five dam building nations include the United States with over 6 390 large dams; India with over 4 000; and Spain and Japan with between 1 000 and 1 200 large dams each Approximately two thirds of the world’s existing large dams are in developing countries . An estimated 1 700 large dams have been under construction in other parts of the world in the last few years. Of this total, 40% are reportedly being built in India Since average construction periods generally range from 5 to 10 years, this indicates a worldwide annual average of some 160 to 320 new large dams per year. 3/26/2019 5

6. TYPES OF DAMS Almost each dam that has been constructed all over the world is unique. This is so because a particular type is chosen because of the considerations of many factors, as discussed in subsequent sections. In fact, dam engineering brings together a range of disciplines, like structural, hydraulics and hydrology, geotechnical, environmental etc Though each situation demands a unique proposal for the type of dam, a broad classification based on the construction material can be made in dividing the types of dams that have been commonly constructed as: 1. Embankment dams, which are constructed of earth fill and/or rock fill, 2. Concrete dams, which are constructed of mass concrete. 3/26/2019 6

7. 1. Embankment dams: 3/26/2019 7

8. 2. Concrete dams 3/26/2019 8

9. How do dams work? Dams store water in the reservoir formed behind the dam The stored water can be used for various consumptive purposes, including use as water for irrigation, or as sources of drinking water for urban and regional towns and cities. The stored water can also be released from the reservoir during the times that natural flows in downstream rivers are inadequate to help meet a variety of environmental objectives Depending on the catchment area for the dam, the water stored in dam reservoirs is usually easier to treat to a drinking water standard than other sources of drinking water, such as run of river supplies. This is because the long time spent in storage usually improves the quality of the water stored in the reservoir 3/26/2019 9

10. benefits of dams? Water supply for domestic, irrigation and industrial use Meeting the agricultural demand for food supply Flood control Hydropower Recreation 3/26/2019 10

11. Water supply for domestic, irrigation and industrial use Dams can provide a cost-effective supply of water for domestic, irrigation and industrial use, when compared to other sources of water, such as recycled water, groundwater, desalination and demand management on a cost-benefit analysis. When determining the suitability of dams all water source options should be assessed based on a cost-benefit analysis 3/26/2019 11

12. Meeting the agricultural demand for food supply The water stored in dams is critically important to many towns in rural and regional Australia, as they are often the main source of water supply. The dams have enabled many regional and rural towns to prosper and develop economically-important agricultural industries. The 2014 Agricultural Competiveness Green Paper identifies 27 potential new dam sites in Australia that would help develop new food growing regions. 3/26/2019 12

13. Flood control Whilst not always their primary purpose, dams provide the opportunity to attenuate flood flows, by their ability to store large volumes of water and then constrain the rate of outflow to downstream rivers through spillways or other release structures. 3/26/2019 13

14. Hydropower Hydroelectricity is electrical energy generated when water that flows down rivers, streams or waterfalls is channelled through water turbines. In Australia, hydroelectric power is most commonly generated from water is that is stored in dams and then released from the dam through water turbines In 2011, hydroelectricity produced 67 per cent of Australia’s total clean energy generation 3/26/2019 14

15. Recreation Dams provide opportunities for communities to undertake various recreational activities, such as sailing, boating and fishing. From a public health perspective it is highly preferable if this onwater recreational activity occurs on dams that store water that is not going to be used as a source of drinking water. Dams can also promote local tourism. 3/26/2019 15

16. Dams and climate risk There is a complex relationship between climate, weather, rainfall and stream flows into dams The proportion of total rainfall from heavy falls will increase in the 21st century over many areas of the globe A one-in-twenty year maximum daily rainfall event is likely to become a one-in-five to one-in-fifteen year event by the end of the 21st century in many regions 3/26/2019 16

17. Costs of dams? Large amount of Cost is required 3/26/2019 17