Resource Potential
The amount of water power available for a particular site can be determined
using the following formula:
Water Power = Head x Flow x Gravity x Density
where
 "Water Power" is given in watts
 "Head" is given in metres
 "Flow" is the volumetric rate at which water is moving through
the pipe, in cubic metres per second
 "Gravity" is the acceleration due to gravity and is approximately
equal to 10 metres per secondsquared
 "Density" is the density of water and is approximately equal
to 1000 kg per cubic metre
The static head (or gross head) is equal to the vertical distance
in metres between the water intake of the system and the point where the
water enters the generator. For reaction turbines the static head includes
the vertical distance from the turbine to the bottom of the draft pipe
where the water is released.
The dynamic head is equal to the static head minus the friction
head losses that occur in the pipework (penstock) between the water intake
point and the hydroelectric generator, and is used to determine the amount
of water power available.
The amount of water power that can be harnessed and converted into electrical
power also depends on the efficiency of the turbine, and the efficiency
of the electric generator.
