In a hydroelectric dam, the water stored in the reservoir has a high potential energy due to its elevated position. When the water is released to flow down through the dam, this potential energy is converted into kinetic energy as the water moves and flows downwards. Therefore, at the top of the dam, the water has high potential energy and lower kinetic energy, and as it flows down, its potential energy decreases while its kinetic energy increases.
To summarize: At the top of the dam, the potential energy is high and kinetic energy is low; as the water flows down, potential energy decreases and kinetic energy increases.