As the Idukki Hydroelectric Project completes fifty years of power generation this year, Kerala finds itself reflecting on one of the most transformative engineering undertakings in its history and confronting new questions about the future of hydropower in a fragile mountain landscape.
The Idukki Hydroelectric Project, Kerala’s largest hydropower installation, completed 50 years of operation in February 2026, marking a major milestone in the state’s energy history.
Built across the Periyar river between the granite hills of Kuravan and Kurathi in Idukki district, the project consists of three dams: the Idukki arch dam, the Cheruthoni gravity dam, and the Kulamavu dam, which together create a vast reservoir spread across nearly 60 square kilometres.
Construction began in 1963 with Canadian assistance under the Colombo Plan, and the project was formally commissioned in 1976 by Prime Minister Indira Gandhi. The arch dam, rising about 169 metres, remains among the tallest of its kind in Asia and stands as one of the most ambitious engineering undertakings in India’s hydropower sector.
Electricity from the reservoir is generated at the underground powerhouse at Moolamattom, one of the largest underground hydropower stations in the country. The plant has an installed capacity of 780 MW produced through six Pelton turbines of 130 MW each, making it the backbone of Kerala’s hydropower system for decades.
Over the years, the project has played a crucial role in meeting the state’s electricity demand and stabilising the power grid. As the project enters its golden jubilee year, the Kerala State Electricity Board has also begun discussing an Idukki Extension Project that could add another 800 MW of capacity, though the proposal is still awaiting statutory clearances.
When the turbines beneath the mountains of Idukki began turning in the mid-1970s, the project symbolised a decisive leap into modernity for a state struggling with chronic electricity shortages. The massive arch dam held back a vast reservoir that promised to illuminate homes, power industries, and stabilise the state’s development trajectory.
Half a century later, the dam’s anniversary arrives at a moment when the rivers of the Western Ghats are behaving differently, extreme rainfall events are reshaping the hydrology of the region and public debates around dams have become sharper than ever before.
What once appeared to be an engineering triumph now sits inside a much larger conversation about climate change, ecological limits and the future of energy. The occasion also raises the larger question of whether such dam projects are anymore feasible in mountainscapes like Idukki where fragile ecology and looming disasters co-exist. Deforestation, changes in land use patterns, climatic shifts and altered rainfall behaviour have made the debate even more complex.
The Idukki Hydroelectric Project is not merely a dam, but a coordinated system of infrastructure built deep within the mountains.
At the time of its commissioning, the project dramatically altered the state’s electricity landscape and emerged as one of the global models of hydropower generation.
“In the 1970s Kerala was facing severe power shortages,” recalls Jumaila Beevi, executive engineer of the Idukki project. “Industries were struggling and power cuts were frequent. When Idukki came online it gave the state confidence that it could manage its energy needs.”
For decades, the dam provided a significant share of Kerala’s electricity supply and enabled the expansion of rural electrification, small industries and urban infrastructure.
The project was considered one of the most ambitious hydroelectric ventures undertaken in India at the time. But the most extraordinary engineering feat lay beneath the mountains.
The Moolamattom powerhouse was constructed deep underground, connected to the reservoir by long water tunnels bored through granite. Workers spent years blasting rock inside narrow tunnels to create the conduits through which water now rushes towards the turbines.
“Those were extremely demanding working conditions,” says Beevi. “There were fewer machines and more manual labour. People risked their lives drilling through rock for hours. But there was also enormous pride. Everyone believed this project would change Kerala.”
The construction of the project transformed the once remote high ranges of Idukki into bustling settlements. Temporary worker camps gradually evolved into permanent townships around Vazhathope, Kulamavu and Moolamattom.
Families recall years when the sound of blasting echoed across the hills and thousands of labourers worked around the clock.
“We grew up hearing stories about the tunnels,” says Leela Joseph of Cheruthoni, whose father worked as a technician at the powerhouse. “When the generators started running, people felt they were part of something historic.”
Yet the reservoir also submerged villages, farmland and forests. Families were relocated to new settlements and many lost ancestral land beneath the waters that now power the turbines.
The social and environmental cost of large dams was rarely discussed during that era of development.
Even today, the Idukki project plays a crucial role in Kerala’s electricity system. Hydropower has a distinct advantage over many other energy sources: it can respond quickly to fluctuations in demand.
When electricity consumption rises sharply during evening hours, water stored in reservoirs can be released immediately to generate power.
“Hydropower is extremely valuable for balancing the grid,” says Minhaj Alem, chairman of Kerala State Electricity Board. “Unlike solar power, which depends on sunlight, hydel stations can ramp up generation quickly when demand peaks.”
As renewable energy sources expand, this flexibility has become even more important.
Yet the river system feeding the Idukki reservoir is undergoing significant changes.
Climate scientists studying rainfall trends across the Western Ghats have observed increasing variability in monsoon patterns. Instead of steady rainfall spread across the season, precipitation often arrives in short bursts of intense storms.
“Climate change is altering the hydrology of the Western Ghats,” explains Roxy Mathew Koll, climate scientist at the Indian Institute of Tropical Meteorology. “We are seeing more extreme rainfall events and longer dry spells. This makes water management for reservoirs much more complex.”
Kerala’s devastating floods in 2018 and 2019 highlighted the challenges of managing multiple dams during extreme rainfall events. Reservoir levels rose rapidly and spillway gates had to be opened to release water.
The dramatic release of water from the Cheruthoni spillway during those floods remains etched in public memory.
The Periyar basin, where the Idukki project is located, is also one of the most ecologically significant landscapes in southern India. The surrounding forests form part of the Western Ghats biodiversity hotspot and include the Periyar Tiger Reserve.
Scientists say large infrastructure projects in such landscapes require careful ecological consideration.
“Hydropower is often described as clean energy,” says V S Vijayan, former chairman of the Kerala State Biodiversity Board. “But dams also transform ecosystems. They alter river flows, submerge forests and fragment habitats.”
The reservoir created by the Idukki project itself replaced large tracts of forest and agricultural land.
Over the decades, roads, tourism and settlement expansion have added further pressure on the surrounding ecosystems.
The anniversary of the Idukki project also coincides with renewed discussions about the future of the ageing Mullaperiyar dam upstream.
Built in the nineteenth century, Mullaperiyar continues to divert water from Kerala to Tamil Nadu under a colonial era agreement. Proposals to construct a new dam have intensified in recent years.
While some view the proposal as a necessary safety measure, others fear that large new construction activities inside the sensitive Periyar basin could create additional ecological stress.
“Any major intervention in this region must consider the cumulative impact on the Western Ghats,” says environmental activist Veena Maruthoor. “These mountain ecosystems are already vulnerable to landslides, deforestation and climate variability.”
Kerala’s geography places natural limits on further hydropower expansion. Most major river basins in the state already contain dams and reservoirs.
Environmental regulations and public resistance have also made new large projects increasingly difficult.
Energy experts therefore argue that the future lies in improving the efficiency of existing infrastructure.
“Instead of building many new dams, we should optimise current hydropower systems,” says energy expert C Jayaraman. “Better forecasting, modern turbine technology and pumped storage systems can increase generation without major ecological disruption.”
Kerala is rapidly expanding solar power through rooftop installations and floating solar plants. Battery storage technologies are also advancing.
Yet hydropower remains critical for balancing the variability of renewable energy.
“Hydropower will continue to play a stabilising role in energy systems dominated by solar and wind,” says Alem. “But we must manage rivers carefully and ensure ecological sustainability.”
For Kerala, the future energy strategy may depend less on building new dams and more on integrating solar, storage and existing hydropower infrastructure.