What is the Difference Between Lake and Reservoir?

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The main difference between a lake and a reservoir is their formation process. A lake is a naturally occurring body of water, formed when surface-water runoff and groundwater seepage accumulate in a low spot, relative to the surrounding countryside. In contrast, a reservoir is an artificial lake created by building a dam on a river. Reservoirs are often used to store water for various purposes, such as flood control, irrigation, and hydroelectricity generation. Here are some key differences between lakes and reservoirs:

  • Formation: Lakes are formed naturally through geological processes, while reservoirs are created by humans to store water.
  • Shape and Depth: Lakes tend to be deepest at the center and more round in shape. In contrast, the deepest part of a reservoir is closest to the dam, while the shallowest point is further upstream.
  • Water Level Changes: The water levels in reservoirs can change rapidly to meet human needs, while lakes adjust more slowly with the seasons.
  • Ecological Impact: Reservoirs can have negative environmental impacts, such as altering the natural course of rivers, stopping the flow of sediments to the ocean, and hindering the free movement of marine life, especially fish.

Despite these differences, lakes and reservoirs share similarities in their physics, chemistry, and biology. They both support freshwater ecosystems and provide essential water resources for human use.

Comparative Table: Lake vs Reservoir

A lake and a reservoir are both large bodies of water, but they have some key differences:

Property Lakes Reservoirs
Origin Naturally occurring body of water Artificial and human-made, created by constructing a dam on a river
Secchi Depth Generally deeper Generally more shallow
Temperature Somewhat lower Somewhat higher
Management Less managed More managed

Lakes are diverse and can have different types of water, with nearby geological structures influencing them greatly. On the other hand, reservoirs are more specific and are created to provide a water resource for humans, such as drinking water or hydroelectricity. This distinction means that reservoirs are often more managed and regulated than natural lakes.