Addressing China's critical water challenges demands more than infrastructure alone. It requires intelligent, data-driven hydrological information systems. This book presents a comprehensive framework for modern hydrological monitoring, grounded in a mobile-prioritized, data-automated, emergency-ready operational model. It systematically introduces the latest monitoring technologies and their practical applications across China, covering precipitation, water level, flow, sediment, groundwater, water quality, ecological monitoring, subaqueous surveying, telemetry, and data management. With forwardlooking perspectives on smart hydrological systems, this volume serves as an essential reference for researchers, engineers, and policymakers seeking to bridge cutting-edge technology with real-world water management challenges.