I.

Introduction

Water Cycle or Hydrologic Cycle, series of movements of water above, on, and below the surface of the earth. The water cycle consists of four distinct stages: storage, evaporation, precipitation, and runoff. Water may be stored temporarily in the ground; in oceans, lakes, and rivers; and in ice caps and glaciers. It evaporates from the earth’s surface, condenses in clouds, falls back to the earth as precipitation (rain or snow), and eventually either runs into the seas or reevaporates into the atmosphere. Almost all the water on the earth has passed through the water cycle countless times. Very little water has been created or lost over the past billion years.