Climate variability, such as El Niño/Southern Oscillation and Pacific Decadal Oscillation, as well as long-term climate change can have a significant impact on the sustainable management of ground water resources. Changes in temperature and precipitation can change the timing and amount of ground water recharge, alter the fraction of precipitation returned to the atmosphere by evapotranspiration, and increase human demand. This session presents aspects of climate impacts on ground water management, including applying general circulation models.