Answer : (1) Potential energy (2) Mechanical energy
Explanation :
In calm water, the water particles do not move. So, the potential energy is stored in the pond water.
Mechanical energy is the sum of potential and kinetic energy. The waterfall has energy equal to the mechanical energy i.e kinetic energy and potential energy both.
At the top, the waterfall has only potential energy (= mgh). When it falls down, the potential energy gets converted into kinetic energy (energy due to motion).