Summary of lectures . — L. : LGMI, LPI Publishing, 1975. — 44s. Two main types of water cycle on Earth are described: climatic, due to hydrological and meteorological factors, and geological, due to such processes as precipitation lithification, metamorphization of rocks, their graniteization, magmatic activity, etc. d. It is shown that both types of the cycle, having an extremely complex internal structure, are genetically and evolutionarily united by tectonic cycles of the Earth's development. The material of the lectures is presented from the point of view of the system approach. The topic develops as the final section of the course "Hydrogeology", read for hydrology students of hydrometeorological institutes and state universities .