Ganges Under Strain as Warming, Water Extraction and Pollution Deepen Dry Season Stress

A river supporting more than 650 million people faces growing pressure

The Ganges stretches more than 2,500 kilometers from the Himalayas to the Bay of Bengal, draining a watershed of more than 1 million square kilometers and sustaining more than 650 million people. Across that vast basin, lower water levels during the dry months are disrupting farming, navigation and ecosystems, while sudden floods bring a different kind of danger.

The river, also called the Ganga, supplies cities, industry and agriculture. It supports wildlife, provides food and work, and holds sacred meaning for many people. Its growing difficulties connect changes high in the mountains with decisions about wells, dams, crops and sewage far downstream.

Scientists describe increasingly intense drought clusters in recent decades. Reconstructions of regional climate history suggest that extreme dry season lows in important stretches are unusual across several centuries. Navigation that once continued throughout the year now faces interruptions. Large boats have run aground in summer shallows, while irrigation canals that previously carried water for weeks later in the season are emptying earlier.

Climate change is one part of the pressure. Thousands of withdrawals, large and small, remove water from the river. Pumping for irrigation lowers groundwater levels, while dams and barrages redirect flows through canals and gates. Pollution damages water quality and the ecosystems that help the river recover.

The result is a connected challenge for food security, public health and regional stability. Water can arrive too quickly during a storm and become scarce months later. Understanding that changing timing is central to understanding the Ganga's condition.

Snow and ice are changing the headwaters

A reconstruction covering 41 years in the Gangotri Glacier System, which feeds the Bhagirathi headstream, shows how snow, glacier ice, rainfall and groundwater contribute to river flow. Snowmelt supplied an average of about 64 percent of annual flow, glacier ice about 21 percent, rainfall runoff about 11 percent and baseflow about 4 percent.

Baseflow is the slower supply of water that continues feeding a river between rainstorms and periods of melting. At Gangotri, snowmelt and glacier ice together supplied about 85 percent of annual flow, calculated from the study's figures. That makes the timing of freezing, snowfall and melting especially important.

After 1990, the seasonal flow peak shifted from August to July. Winters brought less snow, while summer melting and rainfall arrived sooner. Farmers and dam operators therefore face a peak that comes earlier than the seasonal pattern on which they have depended for generations.

Modeling of the upper Ganga projects more total discharge in some future seasons because of heavier rainfall, even as the share supplied by snow and ice declines. By late century, the contribution from snowmelt could fall substantially, while annual flow could increase, with gains concentrated in warmer months.

Higher annual totals can therefore accompany weaker supplies during long dry periods. Short bursts of water raise flood risks, while communities still need steady flows during weeks without rain.

Glacier losses make monitoring more urgent

The World Meteorological Organization reported another year of severe glacier mass loss in 2024, estimating that glaciers lost 450 billion tonnes of ice. Only one third of major river basins experienced conditions near normal, reflecting a wider water cycle marked by flood and drought risks.

WMO Secretary General Celeste Saulo called for investment and cooperation to address gaps in observations:

Continued investment and enhanced collaboration in data sharing are vital to close monitoring gaps. Without data, we risk flying blind.

For the Ganga headwaters, sustained field monitoring would track river discharge, snow cover, glacier mass and local weather. Those measurements support forecasts of dry season supplies, decisions about hydropower operations and warnings for glacial lake outburst floods, when water held in a mountain lake escapes suddenly.

Why heavy monsoon rain can leave water shortages

The South Asian monsoon delivers about 70 percent of the region's annual rainfall within a few months. Recent years have brought later arrivals in some places, more intense downpours and longer dry breaks. Farmers can experience damaging floods and water shortages within the same season.

Across Asia in 2024, many basins recorded river discharge above normal during wet months. A strong El Nino, warmer air capable of holding more moisture and heated seas contributed to heavy bursts of rain. India experienced deadly floods and landslides in several states, with infrastructure and land management struggling to handle large amounts of rain in short periods.

Intense storms in the Ganga basin can send water rapidly over the land instead of allowing it to soak into the ground. Paved urban surfaces add to that runoff. Groundwater recharge can suffer even during a wet year, leaving less stored water for the following dry season.

A community may consequently face high river levels one month, followed a few months later by sharply lower rivers and wells. Rainfall totals alone give an incomplete picture of how much usable water will remain when it is needed.

Groundwater pumping weakens an essential reserve

The Ganga Brahmaputra aquifer is among the fastest depleting on Earth. Studies have estimated declines of about 15 to 20 millimeters a year in parts of the basin. Rural wells that once helped households through summer scarcity now sometimes yield little water.

Arsenic and fluoride contamination create further risks in pockets of the basin. When river supplies decline, these groundwater quality problems threaten health and reduce the amount of water people can safely use.

Modeling in Bihar shows why the intensity of rainfall matters. Scenarios with more rain falling at low intensity produced better recharge and smaller groundwater declines. Higher annual rainfall delivered through a few heavy bursts did less to replenish underground reserves.

One projection for Nalanda district suggests that up to 0.8 cubic kilometers of groundwater could be lost over 42 years if present extraction continues and rainfall arrives in fewer, heavier events. Managing the problem requires attention to pumping and infiltration, the process through which water enters the soil.

Agriculture is the main user. Boro rice, other water hungry paddy and sugarcane draw large amounts from wells and canals during dry months. Less thirsty crops where suitable, more efficient irrigation and repairs to leaking distribution systems could reduce demand.

Community projects such as check dams and restored ponds can slow runoff and help water enter the ground. Replenished groundwater can also restore baseflow to nearby rivers, linking the health of wells with the health of the channel.

Dams alter flows from the mountains to the delta

Hundreds of dams and barrages have been built or planned on the Ganga's main stem and Himalayan tributaries. Their gates redirect water into irrigation canals or power tunnels. Expert assessments have found that only around 80 kilometers of the river's 2,525 kilometer course now flows without interruption.

That is roughly 3 percent of the river's length, using those figures. Barriers interrupt the movement of water, sediment and wildlife. They can also smooth out seasonal pulses that help replenish wetlands, connect floodplains, flush pollution and resist the inland movement of salt water.

The Farakka Barrage, in the border zone of India and Bangladesh, was designed to manage sediment and navigation. It also reduces dry season flows into Bangladesh. When freshwater discharge falls, salty water can travel farther inland, threatening the Sundarbans, the world's largest mangrove forest.

Smaller rivers across northern Bangladesh and West Bengal already dry out in the hot season, leaving communities without dependable water for crops and livestock. Decisions at large structures therefore affect both major channels and the smaller waterways on which rural livelihoods depend.

Sediment trapped upstream creates another problem. The delta receives less of the silt that naturally helps build its low lying land. Groundwater extraction and the weight of new development contribute to subsidence, meaning the land sinks, while sea levels rise.

Some projections put sea level rise in the Bay of Bengal near or above 1 meter by the end of the century. Worst case estimates for the delta reach around 1.4 meters. Without protective planning, large populations in the lower basin face greater exposure to storm surges, saltwater intrusion and displacement.

Mountain disasters expose infrastructure risks

Investigations following the 2013 Uttarakhand flood and the 2021 Rishi Ganga disaster found that hydropower projects operating or under construction increased local risks through roads, blasting and debris. The projects themselves then suffered heavy damage when floods arrived.

Climate change raises the likelihood of outburst floods and landslides. Designs that rely on past conditions without accounting for changing extremes can increase losses. The sequence of events and observations shows why planning must address both sudden disasters and changes in seasonal flow:

• After 1990, the Gangotri reconstruction shows the seasonal flow peak moving from August to July.
• In 2013, the Uttarakhand flood exposed risks associated with mountain infrastructure and construction.
• In 2021, the Rishi Ganga event brought further damage and scrutiny of hydropower development.
• In 2024, severe global glacier losses and high wet season discharge across many Asian basins illustrated the wider pressures on water systems.

Safer operations require attention to the entire mountain setting, including unstable slopes, sediment and the consequences of sudden floods. The same observations needed for disaster warnings also help operators plan for changing water supplies.

Low flows make pollution more dangerous

Untreated sewage, industrial discharge and agricultural runoff place water quality under pressure throughout the basin. During dry months, less river water is available to dilute waste. Warmer water speeds some reactions and can contain less dissolved oxygen, the oxygen that fish and other aquatic animals need.

Modeling of the heavily industrialized Kanpur stretch examined how climate change, land use and changing flows could affect dissolved oxygen, biochemical oxygen demand, ammonia, nitrate, phosphorus and fecal coliform. Biochemical oxygen demand measures how much oxygen is consumed as organic waste breaks down, while fecal coliform indicates contamination associated with fecal material.

The modeling found a high risk of eutrophic conditions under many scenarios. Eutrophication occurs when excess nutrients encourage heavy growth of algae and other organisms, which can leave less oxygen for aquatic life. Pollutant concentrations rose as streamflow fell.

By the middle of the century, the probability of fish kills increases as periods with low dissolved oxygen become more frequent. Sewage and industrial pollution dominate conditions in the most affected reaches, giving treatment and enforcement a direct role in improving water quality even as temperatures rise.

Wildlife needs clean, connected habitat

Ganga river dolphins, gharials, freshwater turtles and otters depend on connected stretches of healthy river. The dolphin population has fallen from tens of thousands to an estimated 1,200 to 1,800 individuals.

Barrages divide habitat, while water diversions can entangle animals. Low flows reduce dolphin hunting grounds and push the animals into polluted backwaters. Pollution and disrupted connections therefore work together to shrink usable habitat.

Conservation groups and government agencies are expanding protected stretches, improving monitoring and promoting water stewardship with local communities. Environmental flow rules would support those efforts by preserving seasonal pulses and minimum discharges during dry months.

Environmental flows are the water levels and seasonal movements needed to sustain river life. Keeping a minimum amount of water in the channel matters, alongside allowing the larger pulses that connect wetlands and move sediment.

Farmers, electricity suppliers and transport face changing seasons

Earlier snowmelt and an earlier discharge peak reduce water later in the kharif growing season, while erratic winter rainfall complicates rabi planning. Kharif refers to the monsoon cropping season; rabi crops depend on the cooler season that follows.

Heat stress and longer dry spells reduce yields of wheat, pulses and vegetables. Farmers face canals that arrive later or close earlier, and wells that are more likely to run dry during lean weeks. Fishers lose income when fish die or habitat deteriorates. Urban water suppliers face greater difficulty maintaining drinking water quality as pollutants become concentrated.

Hydropower production depends on when water arrives as well as how much arrives. Moving the discharge peak from August to July can disrupt electricity schedules and reduce dependable generation later in summer. Sediment surges after cloudbursts can clog intakes and wear down turbines.

Inland navigation also becomes less dependable. Shallow stretches require lighter loads or seasonal shutdowns, affecting the movement of grain and other bulk goods. Because the basin supports a large share of India's economy, disruptions to water supplies bring higher costs and risks well beyond individual riverside communities.

Shared rivers require shared decisions

India, Nepal and Bangladesh share the Ganga system. Managing floods, droughts and fluctuating flows requires trust and the exchange of information from the mountains to the delta. Many existing treaties were written before climate variability was well understood.

Agreements need to address a wider range of conditions, including thresholds for low flows and release rules that protect downstream communities and ecosystems. Open data, joint forecasting, fair sharing and climate science can help countries plan for scarcity and extreme events.

Regional water politics are becoming more complex. Moves to suspend river treaties on other systems, alongside plans for large hydropower projects on Himalayan headwaters outside the Ganga, show the growing treatment of water as a strategic asset. Breakdowns in diplomacy reduce transparency and weaken flood warnings for communities across borders.

Cooperation also has practical uses beyond negotiations over water volumes. Shared observations improve early warnings, flood zoning and drought planning. Joint work on sediment, wetlands and pollution can strengthen resilience across the basin.

What restoring the Ganga would require

Recovery depends on reducing demand, restoring natural river functions and improving management through better measurements. Pilot projects have shown results when policies treat the river as a living system rather than only a channel for moving water. Practical measures span farming, infrastructure, public safety and conservation:

• Secure environmental flows and protect remaining stretches without barriers so the river can move sediment, dilute pollution and sustain wetlands.
• Retrofit hydropower projects and barrages exposed to high risks for safer, more flexible operation. Retire projects whose risks outweigh their benefits in landslide and flood zones.
• Cap groundwater extraction where withdrawals exceed replenishment, meter large users and invest in micro irrigation to reduce water demand.
• Encourage crops that need less water where conditions permit, with minimum support prices and procurement policies aligned to those choices.
• Recharge aquifers through check dams, percolation ponds and restored floodplains that help rain soak into the ground.
• Enforce sewage and industrial effluent treatment. Move tannery and textile clusters toward zero liquid discharge, which aims to prevent liquid wastewater from leaving the operation.
• Consider regulation of industrial clusters or mergers that make businesses account for pollution costs passed from upstream to downstream.
• Expand networks measuring weather and water, including glaciers and snow, and publish open data for reservoir management and drought planning.
• Strengthen warnings for glacial lake outburst floods, flash floods and heat stress through community drills and communication that reaches exposed households.
• Reduce sand mining, plan for sediment delivery and prepare relocation that accounts for climate risks where danger in the delta is extreme.
• Support citizen science, wetland restoration and local river guardians through programs connecting communities, government and businesses.

These measures connect immediate needs with the river's longer recovery: cleaner drinking water, safer settlements, steadier farm incomes and a healthier delta. They also address the different pressures together, from pumping and pollution to disrupted flows and inadequate monitoring.

Highlights

• The Ganga supports more than 650 million people across a watershed exceeding 1 million square kilometers.
• Snowmelt supplied about 64 percent of flow in the Gangotri reconstruction, and the seasonal peak shifted from August to July after 1990.
• Heavier downpours can increase flooding while leaving less water stored underground for dry months.
• Groundwater declines, river withdrawals, barriers and pollution add to climate pressures.
• Only around 80 kilometers of the river's 2,525 kilometer course flows without interruption, according to expert assessments.
• Lower flows threaten water quality, wildlife, farming, hydropower, navigation and the delta.
• Restoration requires environmental flows, groundwater management, pollution treatment, better monitoring and cooperation among India, Nepal and Bangladesh.