Mullaperiyar Dam is a masonry gravity dam constructed on the Periyar River in Kerala, India. The dam was constructed between 1887 and 1895 by John Pennycuick, and it lies 150km south east of Kochi and 200km north east of Trivandrum. The catchment area of the dam is located entirely in Kerala and not an inter-State river. It is operated and maintained by Tamil Nadu. The water level hit 142 feet for the first time in 35 years in 2014 and again topped its maximum limit in 2018. According to the report of UNU-INWEH, published in 2021, the dam is seismically active with significant structural flaws and places 3.5 million people in danger if it collapses.
