Monsoons and groundwater pumping: How climate change and human interventions drive greening of the Thar desert

Indian Institute of Technology Gandhinagar-led research suggests climate change, increased monsoon rainfall and expanded groundwater pumping have driven substantial vegetation growth in the Thar Desert over the past two decades.

Global drylands occupy about 41% of Earth's land area. These regions are highly vulnerable to anthropogenic climate change and land use transformation and frequently face the threat of desertification. Rising atmospheric water demands and expanding arid zones can limit vegetation growth, yet human interventions such as irrigation and groundwater pumping have created conditions for greening in several dryland ecosystems.

In India, drylands comprise nearly 70% of the total land area and support approximately 1.5 billion people. Among these, the Thar Desert, an arid zone of approximately 200,000 square kilometers across northwestern India and southeastern Pakistan, holds the highest population density of any desert worldwide.

In the study, "Greening of the Thar Desert driven by climate change and human interventions, published in Cell Reports Sustainability," researchers conducted an observational analysis using remote sensing, climate datasets, and hydrological records across the Thar Desert.

Conditions in this arid zone include temperatures ranging from 5°C in winter to over 50°C in summer. Annual rainfall averages around 200 mm, concentrated during the southwest monsoon. Surface water remains limited, making groundwater the primary source for agricultural, residential, and industrial use.

Researchers used satellite-derived vegetation indices, precipitation data from multiple sources including CHIRPS, and groundwater measurements from in situ wells and satellite missions such as GRACE and GRACE-FO.

Groundwater levels were assessed through 728 observation wells across Rajasthan with more than 50% data availability from 1996 to 2021. Of these, 207 wells were located within the Thar region. Groundwater storage changes were also captured using satellite-based terrestrial water storage anomalies from GRACE and GRACE-FO missions.

Between 2001 and 2023, vegetation greenness across the Thar Desert increased by 38%, with gains most pronounced in the north-central areas. Both monsoon and non-monsoon seasons showed measurable greening trends.

Seasonal analysis revealed that rainfall accounted for 66% of vegetation growth during the summer monsoon months, while groundwater contributed 34%. During non-monsoon months, groundwater's influence rose to 67%, with rainfall responsible for only 32%.

Annual precipitation in the region increased by 64%, one of only four major desert ecosystems globally to experience a statistically significant rise during the same period. Thar also recorded the highest population growth among 14 major deserts examined worldwide from 2000 to 2020.

Urban areas expanded by 50% to 800% between 1985 and 2020, and agricultural land grew by approximately 300%. Satellite data showed that much of this development was concentrated in areas where groundwater use intensified.

Rainfall and groundwater extraction together have enabled rapid agricultural and urban expansion in the Thar Desert over recent decades. Continued greening appears possible, as climate models project a 20% to 50% increase in mean annual precipitation through the end of the century under both low and high-emission scenarios.

Groundwater overuse is a critical concern as satellite and in situ observations show long-term depletion, suggesting current rates of extraction may not be sustainable.

Future development will depend on balancing increased monsoon rainfall with efficient groundwater management. Rapid expansion of irrigation, especially through deep tube wells, has raised crop yields but also lowered aquifer levels. Longer and more intense heat waves, rising irrigation demands, and water scarcity during dry seasons may strain the region's capacity to sustain growth.

Thar's transformation reflects how coordinated infrastructure investments, irrigation systems, and energy access can reshape arid environments. As monsoon rainfall trends shift westward, this region may experience further ecological and economic changes.

Continued greening will require adaptation strategies such as drought-resilient crops, improved water recharge, and renewable-powered irrigation to maintain food and water security for a growing population.

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