The diagram provided gives us the representation of the process that takes place inside a hydroelectric power plant used to generate electricity.
Firstly, the water from the river is stored in the reservoir behind the dam, There are two parts of the reservoir that is the high and low level reservoir to keep the power plant active throughout the day. The water from the high level reservoir is released downwards towards the power station in the day. The power station consists of a generator connected to a reversible turbine, when water flows through this turbine it rotates causing the generator to convert mechanical energy to electrical energy and then the generated electricity is supplied to the national grids using the power lines connected between them. Similarly during the night same process takes place in a reverse manner. The water from the lower reservoir is pumped upward and thus causing the turbine and generator duo to perform it's action leading to electricity generation.
In conclusion, the diagram provides us with a clear visual of the overall operation and components involved in generation of electricity starting from water from the river and various components involved towards the final power grid which supplies electricity to our cities. 
The diagram provided gives us the representation of the process that takes place inside a hydroelectric  
power
 plant  
used
 to generate electricity. 
Firstly
, the  
water
 from the river  
is stored
 in the  
reservoir
 behind the dam, There are two parts of the  
reservoir
  that is
 the high and low level  
reservoir
 to  
keep
 the  
power
 plant active throughout the day. The  
water
 from the high level  
reservoir
  is released
 downwards towards the  
power
 station in the day. The  
power
 station consists of a generator connected to a reversible turbine, when  
water
 flows through this turbine it rotates causing the generator to convert mechanical energy to electrical energy and then the generated  
electricity
  is supplied
 to the national grids using the  
power
 lines connected between them.  
Similarly
 during the night same process takes place  
in a reverse manner
. The  
water
 from the lower  
reservoir
  is pumped
 upward and  
thus
 causing the turbine and generator duo  
to perform it's action
 leading to  
electricity
 generation. 
In conclusion
, the diagram provides us with a  
clear
 visual of the  
overall
 operation and components involved in generation of  
electricity
 starting from  
water
 from the river and various components involved towards the final  
power
 grid which supplies  
electricity
 to our cities.