Importance of Dams
Dam or the water reservoir is the most important part of the hydroelectric power plant. It is in the dam where water possessing potential energy is stored. Water from the dam is taken to the power generation unit that comprises of the turbines and generators. Here the potential energy of water is used to rotate the blades of huge turbines. The shaft of the turbine rotates in the generators where fluctuating currents of excessively high voltage are formed, which are taken to the transformers and from there to the national grid.
The water in dams carries lots of mud and sediments, hence lots of sediments are accumulated at the bed of the dam and over the long periods of time there can be excessive quantity of mud in the dam. To remove these sediments conduits are placed at the bottom of the dam so as to remove all the sediments.
Types of Dams
There are two main types of dam: Gravity dams and Arch dams. These have been described below:
1) Gravity dams: The gravity dams are the ones which are supported completely on the bed of the rock. In these types of dams, since there is huge quantity of water in the dams, it exerts excessively high hydraulic pressures on bed of the dam. Thus gravity dams can be constructed only in the places where there is strong structure of the rock so that it can sustain all the forces. Further, this rock structure should be able to prevent the seepage of water. This structure should be earthquake proof so that even in case of occurrence of natural disaster the rock structure remains intact.
2) Arch dams: The arch dams comprise of the convex arch which is supported by the lateral rock walls. While in case of the gravity dams the maximum forces are exerted on the bed of the dam, in case of the arch the maximum forces are exerted on the lateral walls of the dam. The walls should be solid and strong enough to sustain all the visible and invisible forces of water so that the dam remains intact and no untoward incident occurs in the future. To ensure long-term safety of the wall, it is important to keep on inspecting the walls of arch dam regularly. The arch dams are constructed in the narrow canyons with steep sidewalls. In such cases the width of dam does not exceed six times its height.