In order to create a hydroelectric power plant, you need water, hence the prefix hydro-. Most times, people use dams to block the water, which in a way stores it. When you need to produce electricity, you release some of the water which flows through a turbine making it spin, which then activates a generator to produce electricity.
Biosphere. It is the highest level of organization. It is the global ecological system which consists of all the living organisms and other factors which supports life.