In most developing countries, the growth of urban public service infrastructure strives to keep up with population growth. Residential Water Use (RWU) in over half of total municipal water consumption in most urban areas in developed countries face similar challenges. For example, consider the Municipality Water Supply Utility (Perusahaan Daerah Air Minum/PDAM) Tirtawening, Bandung; in the last 10 years, the average urban water coverage services have grown at a rate of 0.65%, while the Bandung municipal population growth rate is 1.42% per year. PDAM select and prioritizes their project portfolio based on Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis as well as on its resources availability. A significant body of research exists which assesses the tools and techniques to optimize a project portfolio. Project Management Body of Knowledge (PMBOK) 5 th edition mentions that project interdependencies is a tool to determine and select the project from the Project Portfolio (PP). Most research conducted treated project interdependencies (PI) as a static variable, defined in earlier stage of the PP lifecycle. Apart from that, the importance of a dynamic PI model that is developed using the System Dynamics (SD) approach is not yet recognized as a tool and technique for project portfolio selection The outcomes of this research suggest that the project interdependencies model developed through the SD approach can be one of the available tools and techniques used to assess project interdependencies and determine project priority in order to optimize the project portfolio.