This book represents different types of progress in hydrogeology, including conceptualization changes, different approaches to simulating groundwater flow and transport new hydrogeophysical methods. Each chapter extends or summarizes a recent development in hydrogeology, with forward-looking statements regarding the challenges and strengths that are faced. While the title and scope is broad, there are several sub-themes that connect the chapters. Themes include theoretical advances in conceptualization and modeling of hydrogeologic problems. Conceptual advances are further tempered by insights arising from observations from both field and laboratory work.​