The Water Cycle

Water is being continuously exchanged between the Earth’s crust and the atmosphere. The force of gravity and the heat from the sun cause this exchange to occur. Mankind did not realize this apparently simple concept until it was finally disclosed three centuries ago when the origin of springs was finally understood. The water balance allows to analyze the hydrological cycle by accounting for the water that is found in the atmosphere, soil, subsoil, rivers and lakes, glaciers and ice sheets, and oceans. The inflows, or receipts on the balance sheet, come from direct flows to the Earth’s crust. The exits are provided the Earth’s crust’s outflows. The temporal and spatial scales play a fundamental role in our capability of assessing and predicting water inflows, storage, and outflows in drainage basins.