Technical Abstract: In recent decades, humans have altered atmospheric concentrations of carbon dioxide and other greenhouse gases dramatically. The consequent effects on global and regional climates are uncertain and remain controversial, but changes in the mean and variance of climate variables must be anticipated with careful investigations of potential effects of climate change scenarios on terrestrial hydrology. This special section of the Vadose Zone Journal is an outcome of the international conference on Groundwater Resources Assessment under the Pressures of Humanity and Climate change (GRAPHIC) in Kyoto, Japan, 4-6 April 2006. GRAPHIC is a collaborative effort and umbrella for international research and education sponsored by UNESCO’s International Hydrological Programme (IHP), and the conference was hosted by the Research Institute for Humanity and Nature (RIHN), Japan. Although GRAPHIC is a fledgling area for international research, the papers herein represent studies from several locations around the world, including Africa, Asia, Australia, Micronesia, North America, and Europe. These case studies are merely a sample of the global work and interest in this area, so we note that this publication is not a comprehensive representation of the state of the science. It is not difficult to identify gaps in the present coverage of problem areas, scientific methods, and generalization of results from both empirical and theoretical investigations. The scientific community has yet to focus its expertise and energies on integrative and complementary research that will provide the basis for confident assessments of the coupled effects of human activities and global climate change on subsurface water fluxes, storage and biochemical quality issues. GRAPHIC promises to be a useful umbrella under which to focus our direction and combined energies toward proactive investigations of likely responses of groundwater to the impending pressures of humanity and climate change.