Groundwater recharge is dependent on climatic conditions, in particular temperature and precipitation. Changes in these parameters strongly impact water flux and residence time in shallow aquifers. In comparison, the impact on deep flow systems is dampened because of the lower hydraulic conductivities and because the overall differences in hydraulic head driving these deep systems are not strongly affected by recharge. Climate-related changes in recharge conditions thus have a subordinate influence on deep flow systems compared to other processes of the long-term geological evolution. Note that the impact of glaciations and permafrost is discussed separately (Section 6.5.1.3).