Flowing water creates energy that can be captured and turned into electricity. This is called hydroelectric power or hydropower. Hydropower is electricity generated using the energy of moving water. Rain or melted snow, usually originating in hills and mountains, create streams and rivers that eventually run to the ocean. The energy of that moving water can be substantial, as anyone who has been whitewater rafting knows. This energy has been exploited for centuries. Since ancient times, hydropower from many kinds of watermills has been used as a renewable energy source for irrigation and the operation of various mechanical devices, such as gristmills, sawmills, textile mills, trip hammers, dock cranes, domestic lifts, and ore mills. A trompe, which produces compressed air from falling water, is sometimes used to power other machinery at a distance. In the late 19th century, hydropower became a source for generating electricity. Hydroelectric energy is the most widely used form of renewable energy, accounting for 16 percent of global electricity consumption. Hydropower is the cheapest way to generate electricity today. That's because once a dam has been built and the equipment installed, the energy source -- flowing water -- is free. It's a clean fuel source that is renewable yearly by snow and rainfall. Hydropower is also readily available; engineers can control the flow of water through the turbines to produce electricity on demand. This book emphasises on theoretical and applied results acquired by the authors in the course of a long time of practice devoted to problems in the design and operation of a substantial number of hydroelectric power plants. The book covers all the foremost components of a hydro power plant, from the upstream end, with the basin for water intake, to the downstream end of the water flow outlet.