Potential Energy  Hydropower
Elevation and potential energy in hydropower.
When a body of mass is elevated against the gravitational force  the increase in it's potential energy can be calculated as
E_{p} = F _{ g } Δh
= m a _{ g } Δ h (1)
where
F _{ g } = gravitational force ( weight ) acting on the body (N, lb_{f} )
E_{p} = potential energy (J, ft lb)
m = mass of body (kg, slugs )
a _{ g } = acceleration of gravity on earth (9.81 m/s^{2}, 32.17405 ft/s^{2})
Δ h = change in elevation (m, ft)
Example  Potential Energy of Elevated Body  in SI units
A body of 1000 kg is elevated 10 m . The change in potential energy can be calculated as
E_{p} = (1000 kg) (9.81 m/s^{2}) (10 m)
= 98100 J
= 98 kJ
= 0.027 kWh
Example  Potential Energy of Elevated Body  in Imperial units
A body with weight (force) 500 lb_{f} is elevated 30 ft. The change in potential energy can be calculated as
E_{p} = ( 500 lb_{f} ) (30 m)
= 15000 ft lb
A body with mass 15 slugs is elevated 30 ft. The change in potential energy can be calculated as
E_{p} = ( 15 slugs ) ( 32.17405 ft/s^{2}< ) (30 m)
= 14478 ft lb
Potential Energy in a Tank or a Reservoir  Spreadsheet Calculator
You can estimate potential elevation energy (hydropower) in a tank or a reservoir by dividing the volume in horizontal slices and calculate the elevation energy for each slice  as it is done in the spreadsheet calculator below:
You can copy the spreadsheet to your Google Drive or to your local drive if you want to use it as a template for your own calculations.
Related Topics

Dynamics
Motion of bodies and the action of forces in producing or changing their motion  velocity and acceleration, forces and torque. 
Mechanics
The relationships between forces, acceleration, displacement, vectors, motion, momentum, energy of objects and more.
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