This is a reprint of a 1959 Soviet publication. The introduction of modern industrial methods into the intensively expanding agriculture of the Soviet Union has caused an active development in many other branches of knowledge. One such sphere, the detailed research of underground water regimes and the extensive utilization of these sources, covering the entire territory of the country, is indispensable for proper irrigation, land reclamation, construction of ponds and reservoirs, as well as for rural water supply. This is of particular importance in the arid southeastern and southern regions. The All-Union Institute of Hydrology and Engineering Geology has therefore printed the present manual with the aim of presenting the principles of underground water processes as the natural result of individual stages in their historical development.