Computer simulations have become an important part of today`s engineering of stormwater, sanitary and water distribution systems. Modeling provides a means to cost-effectively analyze the capabilities of existing systems and evaluate complex improvement alternatives under a wide range of conditions. These models can identify an area where flow capacity may be limited or can assist with locating the optimal site for new relief sewers, pump stations, water storage tanks or booster stations. Models are used to support the design specification process and can evaluate the water quality.