Water, which was taken for granted and assumed to exist in abundance, has become one of our most precious natural resources. Hence hydrological and water management problems represent key areas of applied science in the current worldwide economic and ecological situations. Satellite remote sensing technologies have been used more and more to satisfy urgent requirements for information relating to water resources. Many efforts have been undertaken in Europe to develop appropriate methods and to advance these systems to an operational level. Main emphasis is given to processes in which land surfaces and inland waters are involved, dealing with the estimation of precipitation, the assessment of soil moisture, surface runoff and the forecasting of runoff, be it from rainfall or from snowmelt. Remote sensing methods are of fundamental importance for soil moisture monitoring on a global and on a regional scale. Experimental research has demonstrated that if, in principle, observations in the visible and thermal infrared regions of the electromagnetic spectrum are able to detect the surface moisture of bare soils, microwave sensors are the most promising tools for quantitative estimates of this parameter. A valuable amount of research on this subject has been performed in Europe and is reviewed within the framework of the most advanced international research. Within Europe regional or local aspects and problems dominate. Therefore the efforts and achievements concerned with these areas and applications, and the progress towards operational use, will be focused on primarily. The most advanced and most promising operational applications exist in the field of snow hydrology to improve power production.