Abstract for: Decision trade-offs of sewage treatment intervention for small river rejuvenation

Urban river pollution from untreated sewage remains a persistent challenge in rapidly urbanising cities. Treatment infrastructure often lags behind sewage generation, while a significant gap exists between installed capacity and actual treatment due to inadequate operation and maintenance. These challenges are compounded by governance complexities involving multiple stakeholders with differing goals and incentives. This study examines sewage management strategies for the Varuna River in India. This study develops a System Dynamics model of sewage management for the Varuna River catchment in the urban area, integrating five subsystems covering sewage generation, conveyance, treatment, economics, and river health, grounded in field investigations, stakeholder interviews, and secondary data. The gap between installed capacity and actual treatment performance is as consequential as the gap between sewage generation and treatment capacity. Also, under specific cost structures, topographic conditions, and operational parameters, decentralised infrastructure planning may offer a more robust, financially sustainable pathway for river rejuvenation in small urban rivers compared to centralised planning. The System Dynamics model offers a means of interrogating trade-offs under varying local conditions. Decision-makers at the national level can use the tool to support the allocation of investments in sewage treatment infrastructure across widely varying geographies and can capture the complexities of small river rejuvenation in an accessible way.