Climate variability is the result of external forcing like solar irradiation, but it depends also on terrestrial processes like volcanic eruption, internal global feedback mechanisms such as the interactions among climate and vegetation cover, and on anthropogenic forcing acting on water and climate directly. In this lecture, the orbital forcings due to Milankovic cycles are described and characterized with respect to their periodicity and their impacts on global earth temperature and on water resources systems. The anthropogenic forcing over the last 150‐170 years on climate and water resource systems are discussed and compared with long‐term patterns extending over millennia. It is obvious that the impacts due to human induced greenhouse gas emissions dominate the recent climate changes.The climate induced changes on water resource systems dominate at the global level while regionallydirect human interventions (water management practices) are dominant. Examples for human inducedchanges refer to Aral Sea (Central Asia), like Chad (Central Afrique), the Dead Sea (Near East), lakeUrmia (Iran), and many others. Finally, conclusions with respect to the time horizon of water resources management strategies are drawn.