Hydrodams in Malaysia

HYDRODAMS IN MALAYSIA

Z.L. Melvin

University Putra Malaysia

Faculty of Engineering

1. INTRODUCTION

Water is an important element for the survival of all life on earth. It plays a significant role for people, animals and vegetation. People need water in their everyday life; ranging from daily domestic activities, drinking water supply, agricultural activities and livestock sector. As human population keeps growing the demand for water is now not only for daily usage but it has becoming vital for a wide range of industrial activities. That is why dams are needed in order to obtain water to be distributed in a defined quantity and quality to meet with the demands.

Dams are water retaining structure largely constructed across a river, lake or sea to create a water reservoir for several purposes primarily for water supply. They are mainly built from impervious materials (e.g. earth, natural materials, concrete and rocks). According to world register of dams, there are more than 30,000 water retaining dams around the world (Stewart, 2000). Dams were presumed to provide significant impact to the human civilization and it is believed to continue improve the standard of living. In the earliest time, dams were built mainly for either water supply or irrigation. However, as civilization of human and development took place, dams were built not only to cater the high demand of water supply, but also for flood control and specifically for the generation of electricity.

Hydroelectric energy is generated by a dam when the water passes through the dam and flow into the river below. The more water that passes through a dam, the more energy is produced.

A device called turbine will convert the kinetic energy of falling water into mechanical energy. Then, a generator will convert the mechanical energy into electrical energy and thus, electricity is produced.

1. PROBLEM STATEMENT

Dams have provided a major contribution not only to human civilization but also to the economic development (Truffer et al., 2003, Bratrich et al., 2004). Too often, the benefits of dams come at great environmental and social costs. Dams can destroy ecosystems and cause people to lose their homes and livelihoods. Not only that, dam safety is now becoming a main global concern (Wilde, 2010). Incidents affecting dams have occurred in recent years with severe impacts on man and the environment for example in the case of Bento Rodrigues dam disaster. This has drawn attention to the necessity for taking an approach to the control of safety matters relating to dams.

1. OBJECTIVES

The aim of this study is to understand in depth how hydrodams generate electricity. In addition, this study also intended to identify health, safety and environmental risk associated with dams’ construction and ways to mitigate the risks.

1. LITERATURE REVIEW

4.1 Type of Dams

There are several classifications of dams depending on certain criteria; (1) function, (2) hydraulic design, (3) material of construction, (4) rigidity and most common (5) structural action. The followings are three main types of dams characterized based on structural action;

Gravity dams

A gravity dam resists the water pressure and other forces due to its weight (or gravitational forces). It is usually made of cement concrete making them quite strong, stable and durable. It can be constructed to very great heights only on sound rock foundations and it cannot be constructed on weak or permeable foundations. The initial cost of a gravity dam is usually much higher but the maintenance cost is very low. It usually takes a longer time to build and require more skilled labour.

Earth dams

An earth dam is made of soil and resists the forces exerted upon it (able to withstand an earthquake) mainly due to the strength of the soil. They are usually built in wide valleys having flat slopes and on almost all types of foundations. However, earth dams are not suitable for narrow valleys with steep slopes. Nowadays majority of dams constructed are of this type. Earth dams are usually less expensive. It can be constructed in a relatively short period and does not require skilled labour but on the downside, the maintenance cost of an earth dam is quite high and it requires constant supervision.

Rockfill dams

A rockfill dam is built of rock fragments and stones of large size. An impervious membrane (cement concrete or asphaltic concrete or earth core) is placed on the rockfill on the upstream side to reduce the seepage through the dam. Rockfill dams are quite economical when a large quantity of rock is easily available near the site and it can be constructed quite rapidly. Rockfill dams can better withstand the shocks due to earthquake than earth dams and can be constructed even in adverse climates.

4.2 Importance and Benefits for the Government and Public

The construction of a single or a multipurpose dam is a very important project especially for developing countries because of the domestic and economic benefits one country could gain out of it. As reported in World Register of Dams, among dams that were constructed, 48% are for irrigation, 17% for hydropower (production of electricity), 13% for water supply, 10% for flood control, 5% for recreation and less than 1% for navigation and fish farming.

Dams are crucial for irrigation. As population growth is expected to increase, irrigation must be expanded to increase the food capacity production as there will be higher demand for food supply. Besides food, demand for water is gradually increasing throughout the world with the present world population of approximately 5.6 billion and still growing. Global water demand is expected to rise by 2-3 percent annually but freshwater resources are limited and unevenly distributed. Properly planned, designed and constructed and maintained dams to store water contribute significantly toward fulfilling water supply requirements. Dams and reservoirs are needed to store water and then provide more consistent supplies during shortages.

In many countries, hydroelectric power provides nearly all of the electrical power. Electricity generated from dams is by very far the largest renewable energy source in the world. More than 90% of the world’s renewable electricity comes from dams (International Water Power & Dam Construction, 2007). Hydropower also offers unique possibilities to manage the power network by its ability to quickly respond to peak demands. On the other hand, dams could also act as flood control system. It can be used to control the amount of water flowing in a river after heavy rain. When heavy rain occurs, it is gated by the dam and held in the reservoir like a collecting tank.