This book examines decision support systems for water resources planning, management, and water rights assessments and control. Moreover, the book discusses rational decision making, challenges, the use of information technology, integrated management, modeling for groundwater resources management. Section I deals with hydrological topics, problems, and principles including rainfall and floods, flood mitigation, and risk assessment and their related attributes in the arid regions. Section II addresses the droughts and their analysis, assessment, and impacts. In Section III, groundwater as a significant constituent of the water budget in arid regions is introduced. Threats, recharges, quality, and management options of this resource are also discussed. Section IV deals with water quality. The articles in this section explore contemporary methods for evaluating water quality and implementing treatment protocols. Section V covers the subjects pertaining to the management of water resources. This book garners considerable interest in several arid regions worldwide, particularly in the Gulf area. The articles under this area address laws pertaining to the preservation, recycling, and protection of water resources.