What keeps the Great Lakes full of water? What keeps the Great Lakes full?

The Great Lakes, the largest group of freshwater lakes on Earth, are a marvel of nature. But what keeps them full of water? The answer lies in the natural water cycle and the unique geographical features of the region.

The primary source of water in the Great Lakes is precipitation, which includes both rainfall and snowfall. Precipitation that occurs anywhere in the Great Lakes Basin, whether over the water or somewhere inland, will eventually end up in the Great Lakes.

In addition to precipitation, the lakes also receive water from upstream inflows and groundwater. Upstream inflows refer to the water that flows into the lakes from the rivers and streams that feed them. Groundwater is the water found underground in the cracks and spaces in soil, sand, and rock. It is stored in and moves slowly through geologic formations of soil, sand, and rocks called aquifers.

However, the lakes also lose water. Evaporation, the process by which water changes from a liquid to a gas or vapor, is one of the main ways the lakes lose water. The lakes also lose water through outflow into the St. Lawrence River.

Despite these losses, the Great Lakes don’t run out of water because they have a natural water cycle that replenishes the water they lose. This natural balance helps maintain the water levels in the Great Lakes.

In addition to these natural processes, human-made structures also play a role in maintaining the water levels in the Great Lakes. For example, the Moses-Saunders Power Dam has the capacity to discharge a significant amount of water from Lake Ontario into the St. Lawrence River.

So, the Great Lakes stay full due to a combination of natural processes like precipitation, upstream inflows, and groundwater, as well as human interventions like water level regulations. This balance is crucial for maintaining the health and biodiversity of the Great Lakes ecosystem.