Sustainable water resource management is a multidisciplinary challenge involving the availability, quality, allocation, conservation and long-term resilience of surface water, groundwater and recycled water resources. Increasing population, urbanization, agricultural demand, industrial development, pollution, ecosystem degradation and climate variability place pressure on water systems and make conventional supply-oriented management increasingly inadequate. This chapter develops an integrated framework for sustainable water resource management that combines water- balance analysis, demand management, water-quality assessment, groundwater protection, climate-resilient planning, digital monitoring and participatory governance. A simple mathematical formulation is introduced to represent water availability, demand and storage, followed by an uncertainty perspective for rainfall, inflow, demand and groundwater recharge. The chapter also discusses water-use efficiency, rainwater harvesting, wastewater reuse, nature-based solutions, smart sensing, geographic information systems, remote sensing and artificial intelligence assisted decision support. Attention is given to the water energy nexus and the need to maintain ecological flows and ecosystem services. Applications are considered for urban water systems, agricultural watersheds, groundwater-dependent regions and climate-sensitive communities. The chapter emphasizes that technological solutions should be embedded within transparent institutional arrangements, appropriate pricing and incentives, community participation, equity safeguards and continuous monitoring. A sustainable water system is therefore treated not simply as an engineering supply problem, but as an adaptive socio-ecological system in which hydrological processes, human demand, ecosystem requirements, infrastructure, uncertainty and governance interact. The proposed framework provides a practical basis for planning, monitoring and improving water security while supporting resilient ecosystems and long-term sustainable development.