Knowledge of the formation and history of a lake is important to understanding its structure. The current chemical and biological condition of a lake depends on many factors, including:

How it was formed

Size and shape of the lake basin

Size, topography, and chemistry of its watershed

Regional climate

Local biological communities

Activities of humans during the past century

There are four major areas in the US with an abundance of natural lakes:

Limestone solution lakes of Florida

Mountain lakes of the Pacific Northwest

The heavily glaciated Great Lakes region

The glaciated Adirondacks region of the Northeast