Hydropower Projects and River Flows: Environmental Challenges

A hydropower project is expected to leave enough water in the river below its dam or barrage, and this is usually written into its environmental clearance as an environmental flow condition. When a stretch of river runs dry, when excavated muck is dumped on the banks, when tunnel blasting cracks houses or when the project was cleared without studying these effects, the people affected have legal options. They can complain to the MoEFCC regional office and the State Pollution Control Board, appeal against the clearance in the National Green Tribunal within the time limit, or apply to the tribunal for directions and compensation.

This guide is for villages downstream of a dam or diversion barrage, families living above a headrace tunnel, river-dependent farmers and fishers, and also for project companies trying to understand what the law expects of them. It explains how hydropower affects a river, which approvals a project needs and how flow and muck disputes are taken up.

Where a matter needs legal action, our page on river and floodplain cases before the NGT describes how we handle river disputes, from the first complaint to the tribunal.

The essentials

Does a hydropower project have to leave water in the river?

Yes. A hydropower project is not entitled to take the whole river. Environmental flow, often called e-flow, is the minimum quantity of water that must be released below a dam or barrage so that the river continues to function: fish can move, the riverbed stays wet, villages downstream have water for drinking, cattle and irrigation, and the river can dilute what flows into it. Expert committees that appraise hydropower projects routinely fix an e-flow as a condition of the environmental clearance, often with different figures for the lean season, the monsoon and the months in between.

For the upper Ganga and its main headstreams, the Centre also notified minimum environmental flows in 2018, as seasonal percentages that projects in that stretch must release. Other rivers depend mainly on the EC conditions, state government orders and any directions the NGT or a High Court has given for a particular basin.

So the first practical step for anyone downstream is to find out what flow the project was told to release, at what point it is to be measured, and how compliance is reported. Without that number, a complaint that "the river is dry" is easy to brush aside. With it, the complaint becomes a specific breach of a specific condition.

How does a hydropower project affect a river?

Most Himalayan projects are run-of-the-river schemes. A barrage diverts water into a tunnel that may run for several kilometres through the hillside to a powerhouse, where the water returns to the river. The stretch between the barrage and the powerhouse is the one that suffers. In the lean months, when river flow is low and every litre is valuable for generation, this stretch can shrink to a trickle unless the e-flow is honoured.

Storage dams change the river differently. They hold back water and sediment, release it on a schedule that follows power demand rather than nature, and can cause sharp daily rises and falls downstream when turbines start and stop. Sediment trapped behind a dam starves the river below, which can deepen the channel and affect bridges, banks and farmland.

Where several projects are built one after another on the same river, the effects add up. A river can end up flowing mostly through tunnels with short open stretches in between. That is why cumulative impact and carrying capacity studies of a river basin have become a regular demand in objections and in tribunal proceedings.

Which approvals does a hydropower project need?

The list below is general. Exact requirements depend on the project's capacity, location and the current notifications, so check them for the project you are dealing with.

Land acquisition and rehabilitation are dealt with under the Right to Fair Compensation and Transparency in Land Acquisition, Rehabilitation and Resettlement Act, 2013 and state policies. Disputes about the amount of land compensation go to the authorities and courts under that law, not to the NGT.

Forest approval is often the slowest and most contested permission for hill projects; our page on forest clearance explains how that process works.

What legal sources fix environmental flows?

Muck dumping, blasting and tunnelling: the village complaints

Tunnels and underground powerhouses produce enormous quantities of excavated rock and soil, called muck. EC conditions usually require muck to be placed only at designated disposal sites, with retaining walls, terracing and planting. In practice, muck is often tipped down the slope or straight onto the riverbank because it is cheaper. The next monsoon carries it into the river, raises the bed, smothers fish habitat and can block side streams.

Blasting causes a different set of problems. Families above or near the tunnel alignment report cracks in walls, dried springs and landslips. Springs matter enormously in hill villages because they are often the only drinking water source. Proving that blasting caused the cracks or the drying needs care: dated photographs taken before and after, a list of affected houses, the blasting schedule obtained under RTI, and ideally a technical inspection.

In hill-village complaints that Advocate B.K. Singh has examined, the project's own six-monthly compliance reports to the MoEFCC regional office were often the most useful papers, because they show what the company claimed about muck sites and e-flow while villagers' photographs showed something else. Those reports can be obtained from the regional office or through RTI.

Sudden water releases and downstream safety

When gates are opened or turbines start, the river below can rise quickly. People grazing cattle, collecting firewood, fishing or crossing the riverbed can be caught. Projects are expected to have warning systems such as sirens and signboards, and to inform the district administration before planned releases. Where people are injured or killed, or livestock and property are lost, a claim for relief and compensation can be made before the NGT under section 15, and the police and district administration can act on negligence.

Large dams also raise structural safety questions. The Dam Safety Act, 2021 created a national framework for surveillance, inspection and emergency planning for specified dams. Questions about whether a dam is structurally safe go mainly to those authorities, but the environmental consequences of a failure, or of an ash or muck slide into the river, can come to the tribunal.

Fishers, water mills and farmers: whose loss counts?

The people who lose most when a river is diverted are often not the ones whose land was acquired. Fishers lose fish when the river shrinks and migration routes are blocked by a barrage with no working fish pass. Families who ran water mills lose them. Farmers who lifted water from the river for small irrigation channels find the intake dry. Temples and cremation ghats on the bypassed stretch lose the flowing water that their rites need.

These losses are environmental in nature, and the NGT can award relief and compensation for them under section 15, which covers victims of environmental damage and restitution of the environment. Gather evidence of what was lost and when: fish catch records or statements, photos of the mill or channel before and after, and the panchayat's record. Our page on compensation for pollution and environmental damage explains how such claims are built.

Damage to homes from blasting overlaps with quarry and mining cases, where the same proof problems arise; our guide on blasting damage and compensation covers the kind of technical evidence that helps.

Hydropower in the Himalaya: why cumulative impact matters

The Himalaya is young, steep and seismically active. Glacial lakes, landslides and cloudbursts are part of its normal behaviour, and climate change is making extreme events more frequent. After the 2013 Uttarakhand floods and the 2021 flash flood in Chamoli district, which destroyed one project and badly damaged another, the role of hydropower construction in high-risk valleys has been examined by courts, committees and scientists.

For objectors, the legal point is that an EIA must study real risks, including the project's exposure to floods and landslides and its combined effect with other projects in the same valley. An EIA that treats each project as if the river had no other dams, or ignores glacial and landslide hazards, is open to challenge. For a developer, the same point means that weak disaster studies are now a real litigation risk, not a paperwork issue.

How to complain about a hydropower project's effect on the river

These steps are written for a village or group downstream. A single affected family can follow them too.

Hydropower problems and where to take them

Can a hydropower project's environmental clearance be challenged?

Yes, by an appeal to the NGT under section 16 of the NGT Act. The time limit is 30 days from communication, with a further 60 days possible for sufficient cause. For people who are not the project company, communication is generally taken from the date the clearance is put in the public domain as the EIA Notification requires, but this is often argued, so do not wait. Our page on challenging an environmental clearance in the NGT explains the procedure.

Common grounds in hydro cases are an EIA that did not study e-flows properly, ignored downstream users or fisheries, left out the other projects in the basin, used old or copied data, or gave a poor account of landslide and flood risk. Defects in the public hearing, such as inadequate notice or a hearing held far from the affected villages, are another ground; see our guides on mistakes in an EIA report and objections at an EIA public hearing.

A forest approval under section 2 of the forest law is separately appealable to the NGT under section 16. If you missed both time limits, ongoing breaches of the conditions can still be raised under section 14, which is often the more realistic route once a project is running.

What hydropower developers should get right

• Measure and publish the e-flow. A flow meter and public display at the release point answer most complaints before they reach the tribunal.
• Use only approved muck sites. Contractors cutting corners on muck disposal create liability for the project company, not just for themselves.
• Keep a pre-construction record. A survey of houses and springs before blasting begins protects the company against exaggerated claims and helps honest ones get settled quickly.
• File honest compliance reports. Reports that do not match the ground are the first thing a committee checks, and they damage credibility in every later hearing.
• Plan warnings for releases. Sirens, signboards and advance notice to the district administration are basic safety duties.
• Answer the gram panchayat. A written reply to a village complaint, with action taken, is often what keeps a matter out of litigation.

Companies already facing an application can read our guide on EC conditions not followed, which explains how breaches are proved and answered.

What the NGT will not usually do in hydropower cases

The tribunal rarely shuts down a running power project on general grounds that hydropower is harmful. It looks at specific breaches and specific harm, and its usual orders are directions to comply, studies, monitoring, restoration and compensation. Expect that, and frame your case around it.

It also does not decide land compensation amounts, employment promises in rehabilitation plans or purely wildlife offences, since the Wild Life (Protection) Act is not in Schedule I. Those go to the authorities and courts under the relevant law. And a case based only on fear of a future disaster, without evidence of a flawed study or a broken condition, is unlikely to succeed.

For related river problems, see our guides on riverfront development and floodplain rules, industrial discharge into a river and challenging a forest land diversion.