The delta dilemma: Crisis and the search for solutions

Deltas represent low-lying socio-environmental geographical regions characterized by the dynamic interaction between rivers, land, and oceans. These areas are shaped by a combination of fluvial and marine processes, as well as by human activities, including water management policies and the development of urban trade and commerce. Deltas often host densely populated settlements within vulnerable environments, as they provide an array of natural resources, including fertile soil and water suitable for irrigated and intensive agriculture, fisheries, rich biodiversity, and opportunities for non-agricultural economic activities.

The impacts of climate change on deltaic regions are both profound and undeniable. Unlike earlier debates on the existence of climate change, which have largely been settled by overwhelming scientific evidence, the current focus must shift to understanding localised impacts and developing adaptive strategies. While climate negotiations and policy discussions have extensively addressed temperature rise, shifting precipitation patterns, ocean acidification, sea-level rise, extreme flooding, and biodiversity loss, the specific vulnerabilities of deltaic regions remain underexplored in global climate discourse.

Deltas serve as critical ecological and socio-economic zones, supporting millions of people through agriculture, fisheries, and trade. However, they are also among the most fragile landscapes in the face of climate change. Recent studies underscore that land subsidence, saltwater intrusion, and intensified cyclonic activity are accelerating the degradation of these vital ecosystems (Syvitski et al., 2009; Rahman et al., 2019). Moreover, the interplay between anthropogenic pressures—such as excessive groundwater extraction and infrastructure development—and climate-induced stressors has exacerbated the crisis in these regions.

Addressing these challenges requires integrating deltaic concerns into broader climate adaptation and resilience frameworks. While policies such as the Sendai Framework for Disaster Risk Reduction (2015-2030) and the Paris Agreement emphasise resilience-building, more targeted interventions are needed to ensure sustainable water management, coastal protection, and community-led adaptation in delta regions. The unfolding crisis of deltas is not merely an environmental phenomenon; it is fundamentally a humanitarian and developmental issue, necessitating urgent, science-driven responses to safeguard both ecosystems and human livelihoods.

Deltas in human civilisation
Due to the fertile nature of their river-derived sediments, freshwater availability, diverse ecosystems, and access to both inland and the sea, deltas served as centers of early human civilization, particularly in arid climates—such as the Nile (Egypt), Tigris-Euphrates (Mesopotamia), and Indus (Indus Valley civilization). Over the ensuing millennia, these fertile deltas have functioned as agricultural, fishing, and commercial hubs. Asia is home to the world’s largest and most populated deltas, created by the sediment deposited by mighty rivers descending from the Himalayas. They are considered the ‘rice bowls of Asia: the Mekong Delta, for example, produces over 50 percent of Vietnam’s food resources. Ganges Brahmaputra Meghna Delta, commonly called the Bengal Delta, is the largest in the world, shared between Bangladesh and West Bengal in India and hosting 250 million people. Egypt’s Nile Delta is medium-sized, although the Nile is the longest river in the world.

Climate change challenges
However, Deltas are recognised as one of the most vulnerable coastal environments. They face a range of threats operating at multiple scales, from global climate change and sea-level rise to various hazards (floods, erosion, salinisation, subsidence), local anthropogenic activities, and land-use change. According to one study most of them, are sinking, and a percentage of them have experienced severe flooding during the last two there a decade. The extraction of groundwater in the Delta region, for agriculture, fish farming, and urban and industrial areas creates a vacuum. With climate change, the frequency and intensity of these hazards are increasing and are less and less predictable. Because of the limited freshwater resources and extraction of water from the ground several social and economic purposes are the reality in most of the Delta region. Some of the studies published highlight a concerning trend of groundwater depletion, particularly in areas like the Basanti block, where levels have been decreasing by approximately 1 to 2 meters annually over the past decade due to unregulated extraction. Unfortunately, the comprehensive data on the last 30 years is not available. At a similar level, for the Mekong Delta, annual subsidence rates up to several centimeters have been reported. Excessive groundwater extraction is suggested as the main driver.

As groundwater levels continue to decline, the phenomenon of subsidence occurs due to the compaction of aquifers. Over the last 25 years, the extraction of groundwater in this region has surged dramatically, shifting the delta from a nearly pristine hydrogeological condition to one fraught with severe aquifer depletion. Although the precise causes of this depletion are complex and not entirely understood, it’s clear that excessive groundwater extraction is a leading contributor to the diminishing altitude of the delta. One potential solution to mitigate this issue is the installation of a piped water distribution system, which could significantly reduce the reliance on groundwater. However, this solution comes with a steep price tag, making it a challenging option for many communities.

Compounding the issue is the escalating threat posed by cyclones. Taking the Sundarbans delta as a case study, we observe a notable increase in the frequency of cyclones occurring in the Bay of Bengal over recent decades. This trend is likely a consequence of climate change and the associated rise in sea surface temperatures. For instance, cyclones like Amphan in 2020 and Sidr in 2007 exemplify the growing strength and destructiveness of these storms. Cyclone Amphan, in particular, was alarming as it rapidly intensified into a Category 5-equivalent storm, a phenomenon linked to the exceptionally warm waters of the Bay.

While the total number of cyclones may not have shown significant growth, there has been a marked rise in the occurrence of higher-category storms; specifically, the instances of Category 4 and 5 cyclones—classified as very severe to super cyclonic storms—have increased. Research indicates that pre-monsoon cyclones, occurring between March and May, are becoming more potent as global temperatures rise, while post-monsoon cyclones, which typically take place from October to December, are intensifying at an accelerated rate. This shift in cyclone dynamics heightens the unpredictability of such weather events, complicating early warning systems and disaster preparedness efforts for communities in vulnerable regions.

Saltwater encroachment into estuaries and coastal aquifers poses another pressing challenge, particularly in areas where groundwater is being extracted for human consumption. A comprehensive report highlights alarming trends in the Bengal Delta, where saltwater intrusion has been documented extending up to 240 kilometers inland during dry seasons. This phenomenon occurs predominantly when river flow diminishes due to upstream water extraction for agricultural and domestic use. Increased salinity alters the composition of mangrove species, affecting biodiversity and the overall health of the ecosystem.​Salinisation of soil and water resources hampers crop production, threatening food security and the livelihoods of local communities.

International cooperation and policy responses
The recently concluded UN CCRD (United Nations Convention for Conserving Deltas) Summit, held at the Asian Institute of Technology in Bangkok from March 17 to 20, 2025, provided a vital platform for addressing pressing issues concerning delta regions. An expert panel established by the UN is expected to release a white paper, which will serve as an important reminder of the urgent need for collective action to save and conserve delta areas worldwide. Deltas are not merely geographical features; they are essential to maintaining the ecological balance of air, water, and land.
In this context, the Farakka Treaty, officially known as the Ganges Water Sharing Treaty, represents a bilateral agreement between India and Bangladesh regarding the distribution of the Ganges River’s water at the Farakka Barrage. Signed on December 12, 1996, this treaty will reach its 30-year milestone in 2026. It will be intriguing to observe the next phase of negotiations between the two countries, particularly in light of the challenges posed by diminishing water availability, increased sedimentation, the effects of climate change, and the current geopolitical climate.

A call for urgent action

• Deltas are not merely geographical features; they are lifelines for millions of people and critical biodiversity hotspots. Addressing the threats facing these regions requires urgent action, including:
• Sustainable groundwater management to reduce over-extraction and prevent land subsidence.
• Enhanced early warning systems to mitigate the impact of increasingly severe cyclones.
• Nature-based solutions, such as mangrove restoration and wetland conservation, to enhance coastal resilience.
• Transboundary water governance frameworks that ensure equitable water distribution and ecosystem protection.
• Investment in alternative freshwater sources, such as desalination and rainwater harvesting, to reduce reliance on groundwater.