Water in the Pashupati-Aryaghat segment of the upper Bagmati River Basin in Kathmandu valley, the capital city of Nepal, is excessively polluted. The water quality problem is complex, because of the multitude of involved stakeholders, who have different perceptions on the nature of the problem and on ways to address it. In this research, I studied the intervention processes of the Guhyeswori wastewater treatment plant (GWTP) as a purposeful activity which aimed to transform water quality of the segment from the present state (poor water quality) to the desired state (clean water). For this purpose, I applied the Soft System Methodology (SSM) for framing the complex problem, and in which stakeholders are considered executives for solving the problem. Data was collected through semi-structured interviews with the stakeholders and these were analyzed and interpreted analytically. Firstly, my results indicate that water quality has been an important issue because of its cultural and religious significance. As a consequence, stakeholders were interested in the intervention of GWTP and its processes. Secondly, the stakeholders perceived the GWTP a failed intervention, because it could not deliver the desired state. GWTP was a top-down intervention process that did not include important stakeholders and their available skills and knowledge. Finally, my results reveal that stakeholders wanted to reach the desired state, but they did not shoulder the responsibilities. Based on the results, I offer recommendations for future interventions to transform the centralist management to a decentralized model involving the transfer of management functions to its real users.