India's Hidden Climate Crisis: How Falling Groundwater Threatens Carbon Storage

Bengaluru: India is the world’s largest user of groundwater, a vital resource that supports agriculture, drinking water, industry, and natural ecosystems. While groundwater depletion is known to adversely impact these sectors, its effect on the capacity of ecosystems to absorb atmospheric carbon—and its connection with the water cycle—has remained poorly understood so far, as most earlier studies focused on specific regions, leaving gaps in the national picture.

Against this backdrop, new research from the Indian Institute of Science (IISc) reveals that groundwater depth directly influences how efficiently plants sequester carbon. By leveraging satellite imagery, existing datasets, and statistical models, the researchers evaluated how variations in groundwater levels affect the carbon storage potential of ecosystems.

The study was part of Abhishek Chakraborty's PhD at IISc, supervised by Prof Sekhar Muddu and Lakshminarayana Rao. Chakraborty is currently a postdoctoral researcher at the University of California, Merced.

Optimal Water Availability Essential for Healthy Ecosystem

The researchers calculated water table depth (WTD), the distance between the land surface and underground water, across different regions of India. They also measured plant productivity by estimating Gross Primary Productivity (GPP) and Net Primary Productivity (NPP), which reflect the chemical energy plants produce. In addition, they analysed evapotranspiration (ET), which tracks the amount of water plants release into the atmosphere.

Using these measurements, the team estimated two key indicators:

• Carbon Use Efficiency (CUE), which shows how efficiently plants convert absorbed carbon into growth after accounting for respiration
• Water Use Efficiency (WUE), which reflects how much carbon plants gain per unit of water lost

Plant growth depends on both water (a resource) and carbon (a nutrient). Prof Muddu explained that when water becomes scarce, especially in natural forests and grasslands, plants choose between conserving water and maintaining growth. Groundwater stress, therefore, forces difficult trade-offs, reducing plant efficiency and weakening long-term ecosystem health.

New research links groundwater depth to climate resilience in India (Getty Images)

The study found that in most parts of India, deeper groundwater levels reduce plant productivity and carbon storage efficiency. When plants have to draw water from deeper underground, they grow less efficiently and store less carbon.

However, this pattern changes in wetter regions during the monsoon. In these areas, groundwater levels are very shallow, and heavy rainfall leads to waterlogged soils. Because the water cannot drain quickly, plant roots are deprived of oxygen, reducing productivity despite abundant water. A similar effect was observed in irrigated croplands across the country.

These findings highlight that both too little and too much groundwater can limit ecosystem productivity and carbon storage. Prof Muddu clarified that excessively shallow water tables can cause waterlogging and plant mortality, while very deep water tables limit root access to water, leading to water stress and reduced growth. Most plants thrive under moderate, sustainable groundwater levels. Hence, optimal—not maximum—water availability is essential for healthy ecosystems, productive agricultural systems, and effective climate regulation.

A National Perspective on Groundwater Management

The study provides a national-scale view of how groundwater management affects climate-related processes. The researchers say such insights can help policymakers identify regions facing severe environmental stress due to groundwater overuse and design region-specific strategies for sustainable water and land management. Prof Muddu emphasised that given India’s wide range of ecosystems and diverse patterns of groundwater use, the study was conducted at a national scale to identify regional fingerprints and understand where impacts are most pronounced.

Talking to ETV Bharat, Prof Sekhar Muddu explained that falling groundwater levels threaten drinking water availability, especially in urban areas, and create difficulties for agriculture by increasing dependence on additional irrigation, which in turn requires more energy. This highlights the strong water–food–energy nexus linked to groundwater use. Additionally, natural ecosystems depend heavily on groundwater during dry seasons and droughts. When groundwater is depleted, plant growth is restricted due to insufficient water, reducing ecosystem productivity and carbon uptake. Thus, declining groundwater levels have significant environmental, economic, and ecological impacts, he added.

Conceptual illustration showing how groundwater availability influences plant health and carbon-water interactions across Indian ecosystems (Image: Abhishek Chakraborty)

"In India’s monsoon-driven tropical climate, rainfall is highly variable, with frequent dry spells and drought years," Prof Muddu said. "During these lean periods, groundwater becomes the primary source of water for ecosystems. Without access to groundwater, natural ecosystems would be severely impacted, especially during dry seasons and droughts."

Implications for Climate Change

Talking about the broader climate consequences if large parts of India's ecosystem become less efficient at carbon repossession due to failing groundwater levels, the professor stated that if groundwater depletion limits ecosystem growth, less carbon is sequestered and more remains in the atmosphere. Since vegetation and ecosystems act as natural carbon sinks, reduced carbon uptake weakens this “vegetation pump.” Higher atmospheric carbon levels can intensify climate change, increasing the risk of heat waves and droughts. In this sense, healthy ecosystems act as natural climate buffers, and groundwater depletion undermines that protection.

Groundwater is often seen only as a water source, but treating it solely as a water supply issue ignores its broader climate impact. “We need to recognise groundwater not just as a resource, but also as a vital climate-regulating service,” Prof Muddu emphasised.

Conceptual overview linking water table depth with ecosystem carbon-water processes (left), along with spatial trends in carbon uptake for croplands across India (right) (Image: Abhishek Chakraborty)

Policy Measures for Sustainable Groundwater Management

"The policy or governance changes are urgently needed to manage groundwater sustainably while protecting India’s carbon sinks. While policymakers in India recognize groundwater as vital for the water–food–energy nexus, its connection to carbon and ecosystem health is less known. This formed the basis for conducting the research,” Prof. Muddu said, and emphasised urgent actions, including:

• Demand-side measures: Promote water-efficient agricultural practices, such as flood and drip irrigation, structural reform and, depending upon the agro climatic region-specific crop choices to reduce excessive groundwater use.
• Supply-side measures: Enhance natural groundwater recharge through watershed management and rejuvenation programs.
• Community involvement: Implement social and community-based management to ensure policies are effectively adopted.

Together, these structural, technical, and social interventions can curb groundwater decline while supporting ecosystems and carbon sequestration, he said.

Hope for Recovery

Groundwater is a renewable resource, and its depletion is reversible with proper management. Prof Muddu said, “By improving supply-side measures (recharge) and demand-side practices (efficient water use), combined with targeted monitoring and evaluation, groundwater levels can rebound."

"As groundwater recovers, ecosystems regain water, restoring productivity and carbon sequestration. Past studies show that depleted groundwater has rebounded in several regions, offering hope that coordinated management can restore ecosystem health alongside human water needs," he added.