There has never been an urgent need for innovative water management solutions, as over 2 billion individuals worldwide lack reliable access to pure drinking water and 80% of wastewater is discharged untreated. This chapter explores the possible prospects of combining blockchain technology, the Internet of Things (IoT), and machine learning (ML) in urban water systems. The decentralized and secure ledger architecture of blockchain offers superior transparency and data integrity, which are essential in making resource allocation and monitoring truly effective. Where IoT devices deliver accurate information about the quality and movement of water in real time and where machine learning algorithms can help with optimized water distribution and predictive maintenance, water management systems are becoming smarter and more adaptable. This chapter reviews the challenges of today and provides technical analysis alongside real-world examples of how each can enable us to address water scarcity, pollution, and inefficient distribution. Through a thorough examination of current topics and practical examples, the chapter discusses how blockchain technology could tackle issues such as water scarcity, pollution, and inefficient distribution. Case examples, such as the almost disastrous drought in Cape Town and the water crisis in Flint, highlight the urgent requirement for robust infrastructure and effective governance. These results have considerable impacts on the economy, environment, and social development, supporting the transition of smart cities to more advanced and sustainable water management practices. This chapter is expected to contribute to continuously improving and detailed research and studies, create a pathway for implementing sustainable urban water and wastewater systems and secure those systems to be able to face the future challenges of increasing urban population and climate change.