Water is the most abundant chemical component in the biosphere and probably the most important one. Climate change makes the problems related to freshwater more critical. Climate change is associated with the sea level rise and the intensification of the hydrological cycle, producing more frequent and intense rainfall as well as extended dry periods. Water resources are substantially affected by human activities such as dam building, deforestation, mining activities, land use changes and pollutant loads. The protection of water resources from quality deterioration by point and non-point source pollution discharges is probably the biggest challenge in sustainable water resources management over the decades. Climate change will be manifested mainly by sea level rise and the intensification of the hydrological cycle, producing more frequent and intense rainfall as well as extended dry periods. The chapter also presents some closing thoughts on the key concepts discussed in the preceding chapters of this book.