This research work attempted to model an integrated water management system in an advancing country, Nigeria, that can serve as a hallmark for knowledge-base since there is still limited knowledge and documents on the IWRM modeling practice not just in Nigeria but globally. This research adopted a mixed research design, data collection from respondents was done using a questionnaire while the development of IWRM model was started by reviewing existing literatures on the subject, before further attempt was made to design a systematic approach for the modelling practice.