Final answer:
The largest freshwater lake in the world by volume is Lake Baikal in Russia, and by surface area is Lake Superior in North America. Both are crucial for providing fresh water but are threatened by pollution.
Step-by-step explanation:
The largest freshwater lake in the world by volume is Lake Baikal, located in Siberia, Russia. Lake Baikal is not only the deepest and oldest lake on Earth, it was once considered a pristine environment until recent industrial activity brought pollutants into its waters. In terms of surface area, however, the largest freshwater lake is Lake Superior, which is one of the North American Great Lakes. Lake Superior holds 21% of the world's surface fresh water and is an essential resource. Although Lake Baikal and Lake Superior are the largest in their respective categories, other significant freshwater lakes include Lake Victoria in East Africa, which is the second-largest by surface area, and the high-elevation Lake Titicaca in South America.
It is important to note the distinction between the largest by volume, in which Lake Baikal takes precedence, and the largest by surface area, in which Lake Superior is larger. Freshwater lakes are critical to human survival, not just for water consumption but also for agriculture and industry. As highlighted with the situation of Lake Baikal, pollution is a pressing issue that threatens these valuable water resources.