Good Morning! Nature relies on its own water purification and rotation system. The precipitation is due to the accumulation of water due to evaporation. When the precipitation, which represents the water fall itself, is reduced - that is, the rain decreases -, the water available in soil is also consequently reduced. In another words: Precipitation, therefore, is the water that the rain gives back to us: when it supplies little water, we have, therefore, little water on earth. Hugs!