Precipitation on saturated land, especially land formed into a depression, will form a pond or lake.
Lakes can also get their start from released water vapor and earth movements during a volcano or earthquake, plus precipitation. If a river meets a barrier, either a natural dam or a fabricated one, a lake will result from the buildup of water.
Underground water may rise to the surface through land shifts, erosion, or springs to make a lake. Saltwater lakes can also be created by land cutting off a part of the ocean.
Essentially, wherever water gathers without an outlet, a pond or lake will form.
More than 300 rivers feed Lake Baikal in Russia.