This comprehensive casebook, now in a fully updated sixth edition, spans eastern and western water law and policy issues, focusing on the allocation, use and conservation of groundwater and surface water. The new edition retains its in-depth consideration of water institutions, expands its discussion of federal-state and interstate water relations, and sharpens its coverage of property rights claims and the public trust doctrine. It includes new U.S. Supreme Court cases, along with important recent decisions from other federal and state courts. The role of water law in climate change adaptation is considered throughout.