Holger Treidel is an environmental scientist and works as project coordinator with UNESCO’s International Hydrological Programme in Paris. His work is related to the sustainable management of groundwater resources under the effects of climate change & variability, with particular focus on the complex challenges related to the management of transboundary aquifer systems. He is coordinating the UNESCO project Groundwater Resources Assessment under the Pressures of Humanity and Climate Change (GRAPHIC) and global and regional transboundary groundwater management projects in cooperation with the Global Environmental Facility (GEF). Jose Luis Martin-Bordes is a civil engineer specialized in groundwater resources management and works as project coordinator in the International Hydrological Programme (IHP) within the Division of Water Sciences of UNESCO, Paris, France. He provides support to the coordination of the IHP Groundwater activities including the Groundwater Resources Assessment under the Pressures of Humanity and Climate Change (GRAPHIC), the International Shared Aquifer Resources Management Initiative (ISARM), Groundwater Dependent Ecosystems and Groundwater for Emergency Situations (GWES). Jason J. Gurdak is Assistant Professor of hydrogeology in the Department of Geosciences at San Francisco State University, California, USA. He and his research group address basic and applied questions about sustainable groundwater management, vadose zone and soilwater processes that affect recharge and contaminant transport, groundwater vulnerability to contamination and climate extremes, and the effects of climate change and interannual to multidecadal climate variability on water resources. Since 2004 he has served on the UNESCO project Groundwater Resources Assessment under the Pressures of Humanity and Climate Change (GRAPHIC) that promotes science, education, and awareness of the coupled effects of climate change and human stresses on global groundwater resources.