Which factor causes reservoir stratification to occur?

Reservoir stratification occurs primarily due to differences in water temperature and density. In a reservoir, water layers form as a result of thermal gradients, with warmer, less dense water sitting atop cooler, denser water. This stratification can lead to distinct thermal layers, commonly known as epilimnion (the warm upper layer), metalimnion (the middle layer, where temperature changes rapidly), and hypolimnion (the cold, denser bottom layer).

As temperature varies, the capacity of water to hold oxygen also changes, which can impact aquatic life and overall water chemistry. This phenomenon is critical for understanding aquatic ecosystems and managing water resources, especially in terms of water quality and fish habitat. Differences in temperature and density are fundamental physical principles affecting the distribution of water layers, thus driving the stratification process.

The other options either do not have a direct impact on temperature and density or are consequences rather than causes of stratification.