The Ponmudi Dam is a concrete gravity dam built across the Panniyar river which is a tributary of Periyar river at Konnathady panchayath of Konnathadi village in Idukki district of Kerala, India. The dam was constructed in 1963 as a part of a hydroelectric project. Construction was led by E.U.Philipose, Superintending Engineer, Kerala State Electricity Board. It has a length of 288.80 metres (947.5 ft). The hydropower component of the dam has an installed capacity of 30 MW with firm power of 17 MW, generating 158 GWh annually. Taluks through which the river flow are Udumbanchola, Devikulam, Kothamangalam, Muvattupuzha, Kunnathunadu, Aluva, Kodungalloor and Paravur.

Periyar, IPA: [peɾijɐːr], is the longest river and the river with the largest discharge potential in the Indian state of Kerala. It is one of the few perennial rivers in the region and provides drinking water for several major towns. The Periyar is of utmost significance to the economy of Kerala. It generates a significant proportion of Kerala's electrical power via the Idukki Dam and flows along a region of industrial and commercial activity. The river also provides water for irrigation and domestic use throughout its course besides supporting a rich fishery. Due to these reasons, the river has been named the "Lifeline of Kerala". Kochi city, in the vicinity of the river mouth, draws its water supply from Aluva, an upstream site sufficiently free of seawater intrusion. Twenty five percent of Kerala's industries are along the banks of the Periyar. These are mostly crowded within a stretch of 5 kilometres (3 mi) in the Eloor-Edayar region (Udhyogamandal), about 10 kilometres (6 mi) north of Kochi harbor.