Climate Change Effects on Groundwater Resources: A Global Synthesis of Findings and Recommendations

Climate change is expected to modify the hydrological cycle and affect freshwater resources. Groundwater is a critical source of fresh drinking water for almost half of the world’s population and it also supplies irrigated agriculture. Groundwater is also important in sustaining streams, lakes, wetlands, and associated ecosystems. But despite this, knowledge about the impact of climate change on groundwater quantity and quality is limited.

Direct impacts of climate change on natural processes (groundwater recharge, discharge, storage, saltwater intrusion, biogeochemical reactions, chemical fate and transport) may be exacerbated by human activities (indirect impacts). Increased groundwater abstraction, for example, may be needed in areas with unsustainable or contaminated surface water resources caused by droughts and floods. Climate change effects on groundwater resources are, therefore, closely linked to other global change drivers, including population growth, urbanization and land-use change, coupled with other socio-economic and political trends. Groundwater response to global changes is a complex function that depends on climate change and variability, topography, aquifer characteristics, vegetation dynamics, and human activities.

This volume contains case studies from diverse aquifer systems, scientific methods, and climatic settings that have been conducted globally under the framework of the UNESCO-IHP project Groundwater Resources Assessment under the Pressures of Humanity and Climate Change (GRAPHIC). This book presents a current and global synthesis of scientific findings and policy recommendations for scientists, water managers and policy makers towards adaptive management of groundwater sustainability under future climate change and variability.

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.