The goal of the EU-FP7 project WatERP is more interoperability of software systems along the water-supply chain. Having a better data exchange between different stakeholders along the supply chain shall enable more intelligent decision-support for saving water and energy. In order to achieve that higher degree of interoperability, the WatERP project develops a flexible and extensible communication architecture for the different kinds of tools in use, based on a Service-Oriented Architecture (SOA) which is complemented by a Multi-Agent System (MAS) for service identification and orchestration. One central element of the software architecture is the WatERP Water Data Ware-house which acts as a central data hub between different software systems. Both the SOA-MAS architecture and the WDW are based to the most reasonable extent on OGC's open standards for geospatial data processing and are carefully extended by semantic technologies. In this paper, we sketch the SOA-MAS architecture and explain some details of the WDW.