Lakes are not spread evenly over Earth’s surface. South America does not have many lakes, because the Amazon River drains most of its water to the ocean. Canada boasts nearly half of all the world’s lakes. Most of those lakes were carved out by glaciers.
Lake water may come from many different sources. It might come from rivers, underground streams, rain, melting ice and snow, or any combination of the above. A lake’s water source helps determine how long it will last. Another indicator is how it formed.