There are two main ways to take water and use it to generate electricity in a hydroelectric power plant. The first way is called Blank 4 Question 15 , which is when some of the water from a river is diverted to a penstock and flows to a power plant. The second way is called Blank 5 Question 15 , which is used to flood water upstream to create a reservoir - this water can then be used to flow to the penstock and turn to the turbine