The sewer system of many historical or holy cities is not well associated with the present need. The managing of the sewer system of such cities is very difficult. Karbala, located in central Iraq, is one such city that experiences tremendous pressure on its sewer system due to large visiting population during special religious gathering. As the sewer system of Karbala city is not designed for such high population like many other historic or holy cities, the sewer overflows, inundate the roads, and degrade the environmental due to the polluted sewer during religious gatherings. The problem often becomes critical due to heavy rainfall as the gathering usually happens during monsoon. The modeling of the sewer water quantity with a varying population and rainfall is important for simulating the sewer overflow as well as to manage the sewer system. The modeling of the sewer water quality is also important to understand the possible environmental hazard due to the sewer overflow. In this present study, an attempt has been taken to simulate the spatiotemporal distribution of the sewer water quantity and quality with a varying population and rainfall for the prediction of sewer overflow and possible pollution susceptibility. The Stormwater Management Model (SWMM) will be used in the proposed study. The simulation will be carried out in the city center of the Karbala city where the stormwater network is not fully developed. It is expected that this study will help in the operational management of the sewerage system and mitigate the sewer flooding and related environmental problems.