Flooding in California. Drought and famine in the Horn of Africa. Massive fish kills in Texas and Australia. “Forever chemicals” in US drinking water. Similar headlines are sure to dominate the news in the years ahead. What is sometimes missing from the headlines, though, is an understanding that these diverse problems are related: manifestations of serious underlying stresses on our water systems. These stresses require sustained attention from water managers, scientists, policymakers, and the public, even after the headlines have faded. That attention, in turn, requires a shared understanding of how water systems function, the problems facing them, and the tools available to increase their resilience. This text fills that need by providing the necessary knowledge base for understanding and managing complex water problems. It is geared primarily towards students in water management courses at the undergraduate and graduate levels but will also be a helpful resource for practicing water professionals who want to get new ideas or a broader view of the subject. Rather than focusing on one type of water problem (as many water books do), this text explores the entire gamut of water issues, from dams to desalination, from flooding to famine, from prior appropriation to pumped storage, from sanitation to stormwater. And rather than teaching from one disciplinary perspective (as many water books do), it looks at water problems through a variety of lenses: hydrology, climate science, ecology, and engineering, but also law, economics, history, and environmental justice. The result is a concise yet comprehensive introduction to one of the most critical and demanding challenges of our time: developing just and sustainable solutions to water management.