The Serni River rejuvenation in Rajasthan, India, exemplifies a transformative model for integrated water resource management by blending traditional ecological knowledge with modern hydrological science. Led by Tarun Bharat Sangh since the early 1990s, the initiative restored the degraded Parbati-Serni watershed through over 160 community-driven water harvesting structures, including talabs and check dams. This study evaluates seven structures built in 2023, analyzing their hydrological efficiency, cost-effectiveness, and socio-economic impacts. The structures collectively store 1.4 million kiloliters of water, contributing to an estimated 96 million kiloliters conserved across the watershed, alongside 64 million kiloliters of groundwater recharge. Costing Rs. 4.78 per kiloliter, the approach outperforms conventional projects. The intervention has revived agriculture, reduced crime, empowered women, and restored ecological balance, with perennial flows, native biodiversity, and natural springs re-emerging. Qualitative narratives highlight social cohesion, cultural renewal, and community governance via the Serni Sansad. This case study offers a scalable framework for sustainable watershed restoration in semi-arid regions, emphasizing decentralized, participatory, and ecologically restorative practices for global application.