The articles in this reprint highlight the complex interactions between climate change, human activities, and hydrological processes across diverse regions. They showcase advances in modeling, remote sensing, and artificial intelligence for assessing river dynamics, flood and drought risks, and ecosystem responses. Together, these studies reveal both the progress achieved in understanding hydrological change and the persistent challenges in forecasting, managing, and mitigating its impacts. Overall, the issue underscores the need for integrated, data-driven, and adaptive approaches to enhance water security under a changing climate.