Freshwater Reserves Discovered Beneath Coastal Bangladesh Amid Salinity Stress

Vast freshwater reserves have been discovered beneath the salinity-stressed coastal regions of Bangladesh. Researchers from the Lamont-Doherty Earth Observatory, part of Columbia Climate School, conducted a study published in Nature Communications, revealing two significant freshwater reservoirs located deep underground along the Pusur River in the Ganges-Brahmaputra Delta.

One reservoir extends 800 meters deep and stretches approximately 40 kilometers, while the second reaches 250 meters deep and also spans about 40 kilometers. These reservoirs were formed over the last 20,000 years due to geological processes, where falling sea levels previously exposed land to freshwater, later inundated by rising sea levels, which then trapped freshwater below muddy sediments.

The study utilized deep-sensing magnetotelluric soundings to map the distribution of freshwater, as freshwater is less electrically conductive than saltwater. Although the full dimensions and volume of these reservoirs are still being assessed, estimates suggest they could contain around 10 billion cubic meters of freshwater, equivalent to about 4 million Olympic-sized swimming pools.

However, careful management is critical for sustainable extraction to prevent salinization of the freshwater. The implications of this discovery extend beyond Bangladesh, suggesting similar freshwater reservoirs may exist in other coastal deltas globally, where historical sea level fluctuations have occurred.

The lead author of the study, Huy Le, emphasizes the need for thoughtful water management strategies to utilize these resources effectively while mitigating risks of salinization.