SORU: boş bırakılan yere parçanın anlam bütünlüğünü sağlamak için getirilebilecek cümleyi bulunuz
Hydroelectric power plants use falling water to turn the turbines of generators. Therefore, no heat engine is needed. They are usually located at the base of a dam. They produce practically no air pollution or noticeable water pollution of any kind. — However, they may not always be reliable because of shortage of rainfall, and there are not many good locations remaining in which to build dams.