Impact statement

The future of the Bengal Delta will depend not only on how much water Bangladesh can secure, but also on how wisely that water is managed. This article highlights a wider policy challenge: large water infrastructure can solve an immediate problem while creating new risks elsewhere in a highly interconnected delta, and it emphasizes the need to consider the entire river system rather than evaluating a major intervention only by its local benefits. In 2025, across Europe, a record 602 river barriers, including dams, culverts, and sluices, were removed to restore river connectivity and more natural flows. This emerging emphasis on restoring rather than continually engineering rivers offers a valuable perspective for Bangladesh when considering new large-scale hydraulic infrastructure. This writing therefore encourages a broader discussion about how public investment in water security should be allocated. As climate change, sea-level rise, and population pressure intensify, decisions made today may shape water security for generations and encourage transparent, adaptive, and scientifically informed decisions while preserving the long-term functioning of the delta and beyond.

Basis of analysis and limitations

This perspective draws on historical maps, particularly Rennell’s Bengal Atlas (Reference Rennell1781), historical and contemporary river-discharge records from the Joint Rivers Commission (JRC, Bangladesh), published scientific literature, publicly available project plans, and published observations concerning the hydrological and geomorphological behavior of the Bengal Delta. River channels and surface-water boundaries depicted in the maps were derived from the JRC Global Surface Water Dataset (Pekel et al., Reference Pekel, Cottam, Gorelick and Belward2016), while elevation and topographic context were obtained from the Copernicus DEM global elevation model. The proposed avulsion pathway does not represent a model-derived prediction or a forecast of a specific future river course. The discharge dataset from 1935 to 2015 is compiled from Rahman and Rahaman (Reference Rahman and Rahaman2018), and from 2015 to 31 May 2026 is collected from publicly available documents of the Joint Rivers Commission in Bangladesh (2026b). The average discharge of the dry season (Jan–May) is calculated from the total amount of discharged water and the total counted days. Moreover, the hydraulic infrastructures surrounding the Bengal Delta are documented from the relevant governments website and further verified by the existence of high-resolution imagery from Google Earth Pro.

Although government statements and project-related reports indicate that a detailed feasibility study was completed in 2013 and a Development Project Proposal (DPP) was subsequently prepared, the complete versions of these documents, together with detailed environmental, morphological, design, and sediment-management documentation, were not publicly accessible to the author in a form that permitted independent document-level verification.

The past and present of the Padma river

Historically, the Hooghly represents the westernmost paleo-channel of the Ganges–Padma system, along whose banks the city of Kolkata developed. Over geological time, the lower Ganges–Padma system progressively migrated eastward. Much of present-day southwestern Bangladesh consists of alluvial landforms generated through sustained sediment deposition by the Padma. Over approximately the last ten millennia, the principal course of the river system has shifted consistently eastward from the vicinity of Kolkata toward present-day Bangladesh (Sen, Reference Sen2019; Rudra, Reference Rudra and Mukherjee2022 ). According to geological interpretations, the present Madhumati River once constituted the primary distributary of the Padma, flowing through Jessore and Khulna toward the Swatch of No Ground submarine canyon. Subsequently, the main channel migrated further eastward (Umitsu, Reference Umitsu1993). Rennell’s Bengal Atlas (Reference Rennell1781) indicates that the dominant flow path of the Padma at that time corresponded to the present Arial Khan River, passing west of Shariatpur before joining the Meghna near Mehendiganj in Barisal (Figure 2). This implies that present-day Munshiganj and Shariatpur were once geomorphologically contiguous, separated only by a relatively narrow fluvial channel that later evolved into the modern Padma. The Padma Bridge now spans this evolved channel belt.

Figure 2.

Historical evolution of the lower GBM river system and the location of the proposed Padma Barrage. (a) Major river channels and confluences prior to the 1780’s avulsion, reconstructed from Rennell’s Bengal Atlas, showing the former course of the Padma through the Arial Khan system and the historical alignment of the Brahmaputra–Padma network. (b) Present-day river configuration following major channel migrations and avulsions over the last two centuries.

Figure 2. Long description

A two-panel geographical map comparing historical and modern river configurations.

Panel a, labeled ‘a’, shows the river system prior to 1787. In the Northwest, the Farakka Barrage is marked. The main Padma River flows Southeast, with a proposed Padma Barrage site located West of the Madhumati River. A red oval in the center-East highlights the confluence of the Jamuna and Padma. Further Southeast, another red oval marks the Padma River, now known as Arial Khan. The Brahmaputra River flows along the Northeast, labeled as the now Old Brahmaputra. The Meghna River and Dhaleshwari River are visible in the East, converging near Mehendiganj.

Panel b, labeled ‘b’, shows the present-day configuration. The Farakka Barrage remains in the Northwest. The main river channel has shifted significantly. The Jamuna River now flows directly South to meet the Padma at a new confluence point marked by a red oval. The proposed Padma Barrage is indicated with a black and white striped icon on the main Padma channel. To the Southeast, a large red oval highlights the Migrated Padma after the 1780s, showing a much wider and more complex braided channel system. The Old Brahmaputra is now a smaller channel to the Northeast. The Arial Khan is labeled as the older course of the Padma, located South of the current main flow. The Hoogly River is visible on the Western edge of both maps.

During the 1960s, when India initiated construction of the Farakka Barrage (Figure 3 ), the then-government of East Pakistan considered constructing a complementary structure on the Bangladesh reach of the Ganges. Following the commissioning of the Farakka Barrage in 1975, dry-season discharge into Bangladesh declined substantially (Kawser and Samad, Reference Kawser and Samad2016). Hydrological records from Hardinge Bridge between 1935 and 31 May of 2026 show steep declines in river discharge after Farakka became operational (Figure 4). Compared with the pre-Farakka period, post-1975 dry-season flows declined by around 22% in maximum discharge, 48% in average discharge, and 72% in minimum discharge. Even after the 1996 Ganges Water Sharing Treaty, flows remained far below historical levels (Rahman and Rahaman, Reference Rahman and Rahaman2018; Joint Rivers Commission, Bangladesh, 2026). Prior to the operation of Farakka, freshwater discharge within the rivers of the southwestern Bangladesh remained sufficiently strong to prevent significant saline intrusion (Islam and Gnauck, Reference Islam and Gnauck2011). After 1975, salinity progressively penetrated further inland, degrading agricultural land, contaminating potable water resources, and creating severe threats to both agriculture and public health across the region (Mirza, Reference Mirza1998; Gain and Giupponi, Reference Gain and Giupponi2014; Islam et al., Reference Islam, Talukdar, Akhter, Eibek, Rahman, Pal, Naikoo, Rahman and Mosavi2022).

Figure 3.

Topographic setting and major river systems surrounding the proposed Padma Barrage. The map shows an eastward basin gradient and the connectivity of the Padma–Brahmaputra–Meghna system.

Figure 3. Long description

A topographic map with a color-coded elevation scale from 0 meters (blue) to 584.994 meters (red).

* In the Northwest, the red-orange Rajmahal Hills represent the highest elevation.

* Moving East, the Farakka Barrage is marked with a pink dot and a black-and-white dashed line across the river.

* The Farakka Feeder Canal flows South from this point, while the main Ganges River flows Southeast through a yellow-green region labeled High Barind Tract.

* The Mahananda River joins the Ganges from the North.

* In the East, the wide, braided Brahmaputra River (Jamuna) flows South to meet the Ganges, forming the Padma River in the Southeast corner.

* The Gumani River flows East into this system.

* In the South-central area, the Proposed Padma Barrage is indicated by a pink dot, connected by a purple line to a black-and-white dashed barrier across the river.

* Below this, the Madhumati River is labeled as ‘To be Restored’.

* The Hoogly River is visible in the Southwest.

* A legend in the bottom-left includes a scale bar for 30 K M and a thin black line representing the International Boundary.

Figure 4.

Dry-season (January–May) average discharge of the Ganges River at Hardinge Bridge, Bangladesh, during the pre-Farakka (1935–1974) and post-Farakka (1975–2026) periods. The substantial reduction in discharge following the operation of the Farakka Barrage demonstrates the long-term decline of freshwater availability in Bangladesh and the increasing influence of upstream river regulation. Modified after Rahman and Rahaman (Reference Rahman and Rahaman2018) and Joint Rivers Commission (JRC), Bangladesh (2026).

Figure 4. Long description

The Y-axis is labeled Average Discharge in m super 3 s super -1, ranging from 0 to 4000 in increments of 500. The X-axis represents years from 1935 to 2026 in 5-year intervals.

* The Pre-Farakka period (1935 to 1974) is shown as a blue line. It exhibits high variability with peaks reaching approximately 3700 in the late 1950s and early 1960s. A light blue linear trend line for this period shows a positive slope, starting near 2000 and projecting toward 3500 by 2026.

* The Post-Farakka period (1975 to 2026) is shown as an orange line. Immediately following 1975, there is a sharp drop in discharge. The values fluctuate significantly lower than the previous period, mostly staying between 700 and 2000.

* An overall red linear trend line across the entire dataset shows a negative slope, starting near 2000 in 1935 and declining to approximately 1100 by 2026, highlighting the long-term reduction in water flow.

Potential geomorphological consequences

The long-term eastward migration of the Padma River can largely be explained through regional tectonic controls. The Bengal Basin exhibits a subtle eastward tectonic tilting, causing preferential flow adjustment in that direction (Islam and Tooley, Reference Islam and Tooley1999). During the Holocene climatic optimum, increased temperatures accelerated glacial melting, enhancing both meltwater discharge and sediment supply, thereby significantly intensifying delta progradation throughout the Bengal Delta system (Goodbred and Kuehl, Reference Goodbred and Kuehl2000; Allison et al., Reference Allison, Khan, Goodbred and Kuehl2003).

It must also be recognized that the river systems of the greater Active Delta, comprising Barisal, Faridpur, Madaripur and Gopalganj, depend heavily on the lower Padma distributary network extending from Daulatdia to Shariatpur. Reduction in discharge within these distributaries could similarly intensify salinity intrusion across central-southern Bangladesh. Existing studies broadly support such concerns (Shammi et al., Reference Shammi, Rahman, Islam, Bodrud-Doza, Zahid, Akter, Quaiyum and Kurasaki2017; Haq et al., Reference Haq, Shamsudduha, Zahid, Ahmed, Kamal and Taylor2024; Wahid et al., Reference Wahid, Mainuddin, Chiew, Karim, Nahiduzzaman, Alam and Hasib2025). Salinity intensity along the coastal zone is spatially heterogeneous; it is presently most severe near Khulna and Satkhira, while comparatively lower toward greater Barisal and Bhola. Moreover, the spatial distribution of salinity itself has historically undergone significant shifts (Rahman et al., Reference Rahman, Shamsudduha, Haq, Hanif, Islam, Islam, Biswas and Taylor2025).

A reduction in downstream discharge and sediment transport (if) caused by the Padma Barrage may also alter the hydraulic balance between the Padma and Brahmaputra systems. At present, the Brahmaputra–Jamuna joins the Ganges near the Aricha–Goalundo region, after which the combined flow proceeds eastward under the name Padma; the Padma subsequently joins the Meghna farther downstream near Chandpur. This trajectory is not purely eastward but exhibits a slight southward inclination. If the hydraulic energy of the Padma declines substantially, the Brahmaputra may seek an alternative energetically favorable course, potentially avulsing toward the Arial Khan system through a looped channel configuration (Figure 5). Prior to 1787, the Arial Khan reportedly constituted the principal flow path of the Padma (Rennell, Reference Rennell1781). Such a shift would have profound implications for river morphology, sediment distribution, and infrastructure across southern Bangladesh. These impacts may remain largely invisible during the early stages of project operation, creating an impression of success while delayed geomorphological responses accumulate.

Figure 5.

Conceptual illustration of a potential future avulsion pathway within the lower Padma–Brahmaputra system under altered hydraulic conditions associated with the proposed Padma Barrage. Reduced downstream discharge and flow velocity below the barrage may weaken the hydraulic dominance of the present Padma channel, while comparatively stronger flow from the Brahmaputra–Jamuna system could favor a more direct southward course toward the historical Arial Khan corridor.

Figure 5. Long description

A blue-toned hydrological map with a North arrow in the bottom-left corner.

* In the Northwest, a river channel is blocked by a black-and-white dashed line representing a barrage. Red arrows point toward the barrage, and a label downstream reads Low Flow (Lower Velocity).

* From the North, a wider braided river channel flows South with a label stating Comparatively Stronger Velocity.

* At the confluence of these two systems, a new potential pathway is highlighted with a red-outlined, stippled area. This pathway branches off the main channel and curves South toward the Arial Khan (Older Course of Padma) region.

* Along the main Southeast-flowing channel, two red dashed circles are labeled Possible Cut-off Zone.

* To the West of the main system, the Madhumati River System is visible as a series of smaller, winding tributaries.

As previously noted, the Madhumati River functioned as the principal channel of the Padma system during the early Holocene (Umitsu, Reference Umitsu1993; Islam and Tooley, Reference Islam and Tooley1999). If the barrage project induces increased flow conveyance toward this distributary, the Madhumati could potentially reactivate as a dominant channel. Nevertheless, because the Padma undergoes an approximately right-angled deflection and substantial flow deceleration near Alodiar in Kushtia, significant sediment transport into the Madhumati is unlikely. Instead, sediment response could change upstream of the barrage. This may promote extensive char formation, accelerate bank erosion processes, and intensify the braided morphology of the river system.

An uncertain future and rethinking the Padma Barrage

Bangladesh has initiated a significant number of regional and national short- to mid-term plans addressing water security, sediment control, delta management, livelihood improvement, climate resilience and hazard protection. However, despite a lack of formal post-implementation assessments, it is evident that most of these initiatives failed to resolve critical water-related challenges. In fact, several high-profile projects backfired completely, devastating local ecosystems. A prime example is the idea of constructing riverbank embankments and dams for flood protection; these structures severely disrupted basin-level ecology and fundamentally fractured the dynamic relationship between human communities and water systems in the delta (Asaduzzaman and Rahman, Reference Asaduzzaman and Rahman2016; Khatun et al., Reference Khatun, Talukdar, Pal and Kundu2021; Rahman et al., Reference Rahman, Dawes, Donehue, Donehue and Rahman2022; Kais and Islam, Reference Kais and Islam2023; Iqbal et al., Reference Iqbal, Rahman, Murshed, Islam, Muktadir, Khan and Bala2026). Nevertheless, the Bangladesh Delta Plan 2100 (BDP 2100), a 100-year plan introduced in 2018, attempts to provide long-term direction by managing upcoming challenges, including climate change, water security, and environmental stress (GED, 2018, BDP 2100 Abridged Version). Additionally, this adaptive plan features specific goals for water security and the integrated use of land and water resources (Goals 2 and 6), while emphasizing the balance between water supply and demand for sustainable and inclusive growth under its freshwater strategy (FW1). Regrettably, there has been near-zero visible progress, limited application of the plan as an active guideline, a lack of secured budgeting, and minimal practical implementation. Although this plan claims to be integrated, it largely excludes social dimensions, cultural inclusion, economic diversity, and ethnic identities, while failing to predict the human and industrial future of the delta. It may sound uncomfortable, but at this point, it can easily be assumed that one of the most vulnerable countries in the world is moving forward without a comprehensive, inclusive plan or dedicated budget that can be sustained across different political regimes and circumstances.

Moreover, the neighboring country, India’s National River Linking Project (NRLP) seeks to transfer water from Himalayan rivers toward western and southern India through a large network of dams, barrages, reservoirs and canals. In eastern India, this strategy increasingly affects rivers flowing into Bangladesh through the Ganges-Padma-Teesta system, including the Farakka Barrage, which diverts Ganges water into the Bhagirathi-Hooghly system through a 38-km feeder canal (Joshi, Reference Joshi2013; Shah and Amarasinghe, Reference Shah, Amarasinghe, Narain and Narayanamoorthy2016). India has also expanded irrigation and hydropower infrastructure across the Teesta basin. New diversion canals in West Bengal, alongside upstream hydropower projects such as Teesta Low-Dam III and IV, regulate river discharge and trap sediment before water reaches Bangladesh. Beyond the Teesta, the author has identified nearly 170 existing or planned river-control projects that are now distributed across transboundary catchments in northeastern India and Bhutan, affecting rivers that ultimately flow into Bangladesh. At the same time, China is accelerating hydropower expansion on the upper Brahmaputra in Tibet, including large cascade dam systems (Jyoti Deka, Reference Jyoti Deka2021). Together, these projects could significantly alter the Bengal Delta’s hydrological balance by reducing dry-season freshwater flow, increasing salinity intrusion, and destabilizing river systems across Bangladesh. Therefore, Bangladesh needs a futuristic and global standard, water-based plan that is extensively evaluated and integrated across the entire delta system; includes climate change, agriculture, people, and industry; as well as considers non-physical entities, cultural and economic diversities (Islam et al., Reference Islam, Rahman, Matin, Dey, Talukder, Sanyal, Asadujjaman and Akand2024).

Geographically, Bangladesh has alternative choices rooted in its unique deltaic location. Large-scale rainwater harvesting, freshwater storage, managed aquifer recharge, climate-resilient irrigation, distributary restoration, and improved basin-scale water management may contribute to water security at different spatial and temporal scales. Their potential contributions, however, cannot be assumed to be equivalent to the water volumes anticipated from the barrage and would require systematic comparison in terms of water volume, land-energy, and institutional requirements.