India’s Run-of-River Hydro: Ill-Defined, Under-Studied – and Growing at a Fast Clip

Bharat Lal Seth
Tuesday, March 18, 2014

Run-of-river projects are often portrayed as relatively benign alternatives to large-reservoir dam projects, as projects that don’t submerge large areas of land, displace high numbers of communities, or greatly reduce downstream flows. This friendly image has given a new lease on life to many dam builders around the globe. 

A significant number of the world's proposed dams are being billed as "run of river," including many large dams that are known to have significant social and environmental impacts (see box). India especially has been inundated by such projects.

Pinder River
Pinder River
Photo Courtesy of Vimal Bhai

The headwaters of many Himalayan rivers are teeming with run-of-river hydro project proposals. This mountainous area is said to be suffering from an “MOU (Memorandum of Understanding) virus.” Hundreds of agreements have been signed and great stretches of rivers apportioned to private and public enterprises. The projects are being billed as “non-consumptive” – meaning they are expected to make little change to a river’s flow. You can have your cake and eat it too, we’re being told. But the definition of such projects is obscure, and their impacts poorly understood. Run-of-river has become a kind of greenwashing. 

Let’s examine the official talking points. “From an operational point of view, water can be stored for 18 to 20 hours each day, and released for 4 to 6 hours in order to generate electricity. The length of the tunnel, or the height of the dam does not matter. What comes in must go out on a daily basis.” This is how a senior official of a committee that appraises hydroelectric projects for the Ministry of Environment and Forests described run-of-river projects in India. 

The Ministry of New and Renewable Energy, which is concerned with India’s small hydro projects (less than 25 megawatts), defines it in more restrictive terms: “A weir, one or two meters in height, can be built across a river as a means to divert water to a powerhouse. This water after running the turbines must be returned to the river downstream. In such cases there is no large dam or reservoir and water storage is kept to a minimum,” says BK Bhatt, an expert in the ministry.

The variance in these two definitions may appear to be a matter of semantics, but has serious consequences for the future of free-flowing rivers in India. According to government reports, the existing, under-construction and proposed hydro projects on the headwater streams (Alaknanda and Bhagirathi) of the Ganga will impact flows on more than two-thirds of their length. The majority of river flows will be diverted into tunnels for run-of-river projects. 

Take the case of the Pinder River, the last major free-flowing tributary of the Alaknanda, where a 90-meter-high dam to generate 300 MW was proposed. Land submergence from this project would impact more than 500 families, and subject 20,000 people downstream to reduced flows. In 2007, opposition to the project led to a reduction in the height of the dam by 55 meters, and its conversion to a run-of-river type. 

What this meant was that water would be diverted along an 18-km tunnel running parallel to the river. By using the river’s steep gradient, the long tunnel would ensure that the generation capacity would only reduce to 252 MW. The project continues to face roadblocks, however, in part due to the probable impacts of tunneling through the fragile mountainside; each year landslides in the region isolate the valley’s 20,000 inhabitants.  

There is no protocol followed for blasting through the hillsides, and this has resulted in the drying up of streams, as in the case of the 1000 MW Karcham Wangtoo project on the Sutlej River. Subsidence of land and wall cracks in nearby village homes caused by blasting and tunnelling is a frequently reported occurrence. 

Run-of-river projects also create problems because of the daily flood and low-flow situations they bring. The 1,750 MW Lower Demve project in the Lohit River basin in northeast India is one case in point. “The water levels rise and fall by several feet each day. Fluctuations can range from 70-1729 cumec in one day, everyday in lean season,” says Parineeta Dandekar of South Asia Network of Dams Rivers and People. “Such fluctuations due to peaking power generation will have serious impacts on ecology and safety of people downstream.”  

Run-of-river projects are not benign. Their impacts on downstream river flows can be serious and long-lasting. It is therefore essential that a standardized definition of this type of project be adopted worldwide. They must also be given the same scrutiny as larger-reservoir projects.  And given that they are often not the only dam in a river, their cumulative impacts must also be accounted for before approval. 


Background: When Run-of-River Brings Big Impacts

Proponents of run-of-river projects frequently claim they do not require a reservoir. In reality, all run-of-river dams impound water, either to create “head” for hydroelectricity generation, to raise water levels to the height of diversion intakes on water projects or to create enough depth for navigation. In theory, no dam with gates should be considered run-of-river, because closing and opening gates implies storing and releasing water. In practice, dams with some limited – but undefined – storage capacity are referred to as run-of-river.

Some examples of problematic “run of river” dams include: Maheshwar Dam in India's Narmada Valley, which forced some 35,000 people from their homes; Pak Mun Dam on a Mekong tributary, which caused drastic reductions in fish populations upstream of the dam and harmed the livelihoods of more than 20,000 people;  Chalillo Dam, which inundated 1,000 hectares of riverine habitat in Belize and threatens rare species; the Lower Kihansi Hydropower Project in Tanzania, which brought the endemic Kihansi Spray Toad to extinction, and the 113-meter-high Pangue Dam on Chile’s BioBio River, which displaced 1,300 people, and led to an even bigger dam being built upstream to ensure a more steady flow of power.