Water resources provide human beings with clean drinking water, irrigation water, and industrial water. The hydrological cycle has changed profoundly due to climate change and increasing population. In recent years, the methods used for water resource management and the sustainable development of water resources under changing environments have been constantly pursued through interdisciplinary studies. To manage the rising challenges, a mutual cooperation between research, management, and policy measures should be formed. By using a suitable model to evaluate the status of regional water resources against the background of climate change, the environment adaptability of the vulnerable water resources system can be improved. This book provides comprehensive insight of the fundamentals of engineering hydrology. The study on water resources is gradually expanded to focus on the entire system. The economic-engineering optimization model used for the optimization of the water resources system enriched the evaluation method of the macro-system, which considered data related to surface water, groundwater, water infrastructure, and water demand. Pollution of surface water with harmful chemicals and eutrophication of rivers and lakes with excess nutrients are serious environmental issues.Pollution of surface water with harmful chemicals and eutrophication of rivers and lakes with excess nutrients are serious environmental concerns. This book reviews currently available hydrologic and water quality models, and presents model application case studies, to provide a foundation for further model development and watershed assessment studies. It succeedingly focuses on understanding groundwater storage changes and recharge through remote sensing; an ArcGIS toolbox for river bathymetry reconstruction; hydro-geochemical water inputs identification in glacierized basin hydrology; and hydrologic trends in the upper Nueces river basin of Texas—implications for water resource management and ecological health. This book will be of valued students and practitioners dealing with the associated field and, moreover, may provide new concepts and starting topics for future researches.