HYDRA

From HYDRA web site:

HYDRA® software is a full-featured program used by environmental and civil engineers to model and design urban drainage systems. It helps you estimate wastewater flows, and then calculates the resulting hydraulics within the collection system. It provides tools for managing all types of flows, including sanitary wastewater, stormwater inflow, rainfall-dependent infiltration, and groundwater infiltration. It helps you understand how the whole sewer system works under various conditions — today and in the future – and identify potential problem areas. HYDRA® software creates preliminary design for new sewers and suggests improvements for existing systems. It helps you optimize your pipe network, and find the most cost-effective way to solve system problems. The HYDRA® program has been used by thousands of engineers since its first commercial release in 1973.

For more information see HYDRA web page.