The rolling motion reflects the movement of water. According to the definition of kinetic energy, we know that water has kinetic energy.
The distance between the white clouds on the Yellow River shows that the water is in a very high position relative to the ground. According to the definition and determinants of gravitational potential energy, it can be determined that water has a large amount of gravitational potential energy.
Kinetic energy and potential energy are collectively called mechanical energy. Therefore, it reflects that these two rivers contain a large amount of mechanical energy.
So the answer is: mechanical.