The image is a diagram illustrating the structure of a dam, specifically a hydroelectric dam. The dam is depicted with two main sections: the reservoir and the powerhouse. 

1. **Reservoir**: The reservoir is shown as a large body of water enclosed by a dam wall. The reservoir is divided into two parts by a dam, which is represented by a horizontal line. The reservoir is labeled "Gatun Lake."

2. **Powerhouse**: The powerhouse is located at the bottom of the reservoir. It is connected to the reservoir by a pipeline, which is also shown in the diagram. The powerhouse is labeled "Lock."

3. **Locks**: There are two vertical lines labeled "Lock" that represent the locks used for the operation of the dam. These locks are likely used to control the flow of water through the dam.

4. **Water Flow**: The water flows from the reservoir through the pipeline and then into the powerhouse. This flow is depicted by arrows pointing from the reservoir