The growing emergence of the Internet of Things and the proliferation of smart cities have created significant challenges for software engineering. One of the key challenges in smart sustainable cities is the efficient management of water resources, which has become a global priority. Smart water meters, equipped with sensors and communication capabilities, offer a promising solution for optimizing water management. However, the successful deployment of smart water metering systems requires a robust and scalable software architecture capable of efficiently processing and analyzing large volumes of data to improve decision making. Complex event processing (CEP) has emerged as a powerful technology to address such a challenge since CEP enables real-time definition and detection of complex patterns within data streams, facilitating the identification of anomalies, trends, and critical events. In this chapter we present an effective and efficient CEP-based software architecture for intelligent water management which facilitates an early detection of leaks and frauds, as well as further anomalies. In addition, we have configured and made use of an intuitive graphical user interface that allows domain experts to define custom patterns without the need for programming skills, as well as a RESTful API to manage the patterns deployed within the architecture at runtime.