Lakes are an important source of accessible freshwater. They provide a large supply of freshwater to the planet. How, First, there are a lot of them. There are millions of lakes on Earth, and almost half of them are in Canada. One very large lake, Lake Baikal in Siberia, contains 20 percent of all the freshwater on the surface of our planet. Another way lakes provide a lot of water is that lake water is easy to get – land surrounds a lake on all sides and makes the water fairly calm and quiet. Last, the freshwater supply in lake can come from different sources, instead of just one source. Most lakes are areas that glaciers covered in past. Some lakes form when rocks stop a river from flowing. Lakes also form when rainwater fill the opening of an extinct volcano.