A plan to build a mega reservoir to solve Chennai's growing water crisis is giving people in nearby coastal fishing villages a major headache.

In villages like Kovalam, residents say construction has already disrupted rivers, backwaters and the livelihoods they have depended upon for generations.

The megaproject aims to boost climate resilience for the 12 million people who live in the southern Indian city's metropolitan area. But scientists and activists warn that blocking wetlands and mangrove ecosystems could worsen flooding and coastal erosion elsewhere in Tamil Nadu. What is touted as a big "solution" could end up doing more harm than good.