Howard Wheater is Professor of Hydrology at Imperial College, London. He is past President of the British Hydrological Society, a Fellow of the Royal Academy of Engineering, a Fellow of the Institution of Civil Engineers, and is a life member of the International Water Academy. His research interests are in hydrology and water resources, with wide-ranging applications including climate change, surface and groundwater hydrology, floods, water resources, and water quality. He has published over 200 peer-reviewed papers and six books. Academic awards include various UK prizes and the 2006 Prince Sultan bin Abdulaziz International Prize for Water. He has been extensively involved in flood and water resource projects in the UK and internationally, providing advice to states and international governments. He has a particular interest in the hydrology of arid areas, and has worked in Oman, Saudi Arabia, Yemen, the United Arab Emirates, Jordan, Syria and Egypt, and Arizona. He chairs UNESCO's G-WADI arid zone water resources programme and was invited by the Japanese government to give a keynote address on water scarcity to the 2003 Kyoto World Water conference. Simon Mathias holds a Lectureship in the Department of Earth Sciences at Durham University. Prior to this position he was active in the field of groundwater engineering as a researcher and lecturer within the Department of Civil and Environmental Engineering at Imperial College, London. His principal expertise lies in the development of mathematical models to describe flow and transport of reactive contaminants in porous and fractured porous media. Dr Mathias has worked on a broad range of applications including vadose zone transport of nutrients in fracture rock systems, plant uptake of radionuclides, aquifer characterisation studies, buoyancy driven flow problems, CO2 geo-sequestration and hydraulic fracture propagation. He has published widely in international peer-reviewed journals. Dr Mathias is an elected committee member of the British Hydrological Society. Xin Li is Professor at the Cold and Arid Regions Environmental and Engineering Research Institute (CAREERI), Chinese Academy of Sciences (CAS). His primary research interests include land data assimilation, application of remote sensing and GIS in hydrology and cryosphere science, and integrated watershed study. He is currently director of the World Data Center for Glaciology and Geocryology, Chair of the working group on remote sensing of the Chinese Committee for WCRP/CliC and IUGG/IACS, co-chair of the working group on theory and method of the China Association for Geographic Information Systems, and a member of the American Geophysical Union. He is also the secretary of G-WADI Asia established by UNESCO IHP. He has published over 120 journal articles and monographs. He was recipient of the Outstanding Science and Technology Achievement Prize of the CAS in 2005, First Class Science and Technology Progress Prize of Gansu Province, and the Seventh National Award for Young Geographers in 2003.

• Preface H. S. Wheater, S. A. Mathias and X. Li; 1. Groundwater modelling in arid and semi-arid areas: an introduction S. A. Mathias and H. S. Wheater; 2. Hydrological processes, groundwater recharge and surface water-groundwater interactions in arid and semi-arid areas H. S. Wheater; 3. Conceptual models for recharge sequences in arid and semi-arid regions using isotopic and geochemical methods W. M. Edmunds; 4. Groundwater flow and transport J. Carrera and S. A. Mathias; 5. Performing unbiased groundwater modelling: application of the theory of regionalized variables S. Ahmed, A. Nabi and S. Owais; 6. Groundwater vulnerability and protection A. Butler; 7. Variable density groundwater flow: from modelling to applications C. T. Simmons, P. Bauer-Gottwein, T. Graf, W. Kinzelbach, H. Kooi, L. Li, V. Post, H. Prommer, R. Therrien, C. Voss, J. Ward and A. Werner; 8. Sustainable water management in arid and semi-arid regions W. Kinzelbach, P. Brunner, A. von Boetticher, L. Kgotlhang and C. Milzow; Index.

Howard Wheater is Professor of Hydrology at Imperial College, London. He is past President of the British Hydrological Society, a Fellow of the Royal Academy of Engineering, a Fellow of the Institution of Civil Engineers, and is a life member of the International Water Academy. His research interests are in hydrology and water resources, with wide-ranging applications including climate change, surface and groundwater hydrology, floods, water resources, and water quality. He has published over 200 peer-reviewed papers and six books. Academic awards include various UK prizes and the 2006 Prince Sultan bin Abdulaziz International Prize for Water. He has been extensively involved in flood and water resource projects in the UK and internationally, providing advice to states and international governments. He has a particular interest in the hydrology of arid areas, and has worked in Oman, Saudi Arabia, Yemen, the United Arab Emirates, Jordan, Syria and Egypt, and Arizona. He chairs UNESCO's G-WADI arid zone water resources programme and was invited by the Japanese government to give a keynote address on water scarcity to the 2003 Kyoto World Water conference. Simon Mathias holds a Lectureship in the Department of Earth Sciences at Durham University. Prior to this position he was active in the field of groundwater engineering as a researcher and lecturer within the Department of Civil and Environmental Engineering at Imperial College, London. His principal expertise lies in the development of mathematical models to describe flow and transport of reactive contaminants in porous and fractured porous media. Dr Mathias has worked on a broad range of applications including vadose zone transport of nutrients in fracture rock systems, plant uptake of radionuclides, aquifer characterisation studies, buoyancy driven flow problems, CO2 geo-sequestration and hydraulic fracture propagation. He has published widely in international peer-reviewed journals. Dr Mathias is an elected committee member of the British Hydrological Society. Xin Li is Professor at the Cold and Arid Regions Environmental and Engineering Research Institute (CAREERI), Chinese Academy of Sciences (CAS). His primary research interests include land data assimilation, application of remote sensing and GIS in hydrology and cryosphere science, and integrated watershed study. He is currently director of the World Data Center for Glaciology and Geocryology, Chair of the working group on remote sensing of the Chinese Committee for WCRP/CliC and IUGG/IACS, co-chair of the working group on theory and method of the China Association for Geographic Information Systems, and a member of the American Geophysical Union. He is also the secretary of G-WADI Asia established by UNESCO IHP. He has published over 120 journal articles and monographs. He was recipient of the Outstanding Science and Technology Achievement Prize of the CAS in 2005, First Class Science and Technology Progress Prize of Gansu Province, and the Seventh National Award for Young Geographers in 2003.

• Preface H. S. Wheater, S. A. Mathias and X. Li; 1. Groundwater modelling in arid and semi-arid areas: an introduction S. A. Mathias and H. S. Wheater; 2. Hydrological processes, groundwater recharge and surface water-groundwater interactions in arid and semi-arid areas H. S. Wheater; 3. Conceptual models for recharge sequences in arid and semi-arid regions using isotopic and geochemical methods W. M. Edmunds; 4. Groundwater flow and transport J. Carrera and S. A. Mathias; 5. Performing unbiased groundwater modelling: application of the theory of regionalized variables S. Ahmed, A. Nabi and S. Owais; 6. Groundwater vulnerability and protection A. Butler; 7. Variable density groundwater flow: from modelling to applications C. T. Simmons, P. Bauer-Gottwein, T. Graf, W. Kinzelbach, H. Kooi, L. Li, V. Post, H. Prommer, R. Therrien, C. Voss, J. Ward and A. Werner; 8. Sustainable water management in arid and semi-arid regions W. Kinzelbach, P. Brunner, A. von Boetticher, L. Kgotlhang and C. Milzow; Index.