The giant continent was called...
a. Pangaea
Read it carefully and slowly
Water leaves a lake through the ground. "Ground water is recharged from rain water and snowmelt or from water that leaks through the bottom of some lakes and rivers," - Google
Sorry if my answer was incorrect.
Rainstorms provide natural moisture to the environment. Receiving rain will keep plant life healthy, give animals a natural reservoir to drink from, as well as keeping the life in the river healthy. Though a flash flood may cause damage to buildings and habitats at first, buildings can be fixed and over time, wild flora and fauna will return to the area, often more plentiful, is there is a good amount of moisture <span />
Gravity keeps the water and yourself from falling off the planet into space.
