In the 21st century, the quality as well as quantity will decide about water for humans. Tomaintain its high quality is in the hands of the mankind. Quantitative characteristics of the hydrological cycle will depend on the development of the climatic system. Climate changes cause changes in economical and social spheres of the society in every affected country. Legislative and hydrotechnological measures and constructions will be the main instruments of water management to eliminate the consequences of climate changes. The basic task of hydrology in the changing hydroclimatic system is a careful monitoring of climatic and hydrological elements and processes.