Problem with Saltwater Intrusion in the Coastal Region of Bangladesh

by Mahir Tajwar

Bangladesh, one of the world's freshwater reservoirs, currently faces a significant saltwater intrusion threat. The overall land area of Bangladesh is approximately 2,48,677 square kilometers, of which approximately twenty percent of the land mass is made up of coastal regions. Due to Bangladesh's extensive coastline, the negative effects of saltwater intrusion on the country are severe. Salinity impacts coastal land and water primarily. The salinity levels of soil, groundwater, and surface water in coastal Bangladesh have been increasing over the past few decades. According to the Soil Resources Development Institute of the country (SRDI), the overall quantity of salinity-affected land in Bangladesh was 83.3 million hectares in 1973, 102 million hectares in 2000, and 105.6 million hectares in 2009. Salinity in the coastal region has increased by around 26% over the past 35 years, expanding to the non-coastal regions.

Figure 1: Salinity in the groundwater in the coastal region of Bangladesh

Variations in temperature and precipitation patterns, sea-level rise, changes in frequency and intensity of cyclones, storm surges, and changes in river and soil salinity are the broad categories of climate change effects impacting the coastal regions of Bangladesh. The salinity of coastal Bangladesh's soil, groundwater, and surface water have increased during the past several decades.

Current saline levels have already posed a danger to crop production in coastal regions. Changes in river salinity and the availability of freshwater negatively impact fisheries' natural habitats. The human body requires a specific amount of salt, which it obtains from food and water. However, the concentration of salt in the water in coastal regions is many times greater. When this water enters the body, the health risk increases. It gets increasingly dangerous, particularly for pregnant women. During pregnancy, women who ingest more saltwater develop convulsions and high blood pressure. As a result, the rate of infant mortality among women is also greater, as noted in the World Bank report. In addition, high blood pressure is linked to a high salt intake, which raises the risk of cardiovascular disease. According to experts, coastal residents can lower their blood pressure by consuming less salty water. In order to protect the people of the coastal region from health risks, it is vital to provide clean water.

Fig 2: A layer of salt has covered this dried-up canal in the coastal region

Fig 3: Causes and Impacts of Salinity in the Coastal Region of Bangladesh

Groundwater, which is a major source of fresh water for agricultural and drinking purposes in the region of Hatiya Island, an island in the central coastal region of Bangladesh, is heavily contaminated by natural processes as well as some anthropogenic activity, which has resulted in a variety of adverse impacts on human health. The shallow aquifer, which is at a depth of 30 to 40 meters, is highly polluted with arsenic and is unsuitable for usage. Thus, the people of this region rely greatly on the intermediate aquifer which is at a depth of 60 to 120 meters. Our investigation analyzes intermediate groundwater aquifers based on hydrogeochemical characterization and suitability for irrigation and drinking uses on different indices utilizing a combined geochemical method, multivariate statistical approaches, and some geospatial analysis. The drinking water quality index map indicates that six of the groundwater samples are in good condition and fit for human consumption, while nine of the samples exceed the water quality index's standard limits and are therefore unfit for human consumption. Based on the values of Sodium Absorption Ratio, Soluble Sodium Percentage, and Residual Sodium Carbonate, 7 of the groundwater samples are inappropriate for agricultural use, but 8 samples are in excellent or good condition for usage.

Fig 4: Groundwater suitability indexing in the region of Hatiya Island

In conclusion, the issue of saltwater intrusion has received very little attention in the past. It has become vital to investigate the possibility of increasing the potential of the coastal regions of Bangladesh to supply fresh groundwater for the livelihood of the people residing in the coastal regions. It is crucial to address the issue of land salinization by implementing long-term land management policies. This study can be used to assess the condition of groundwater quality in the study region and evaluate the extent of contamination in Bangladesh's coastal region.


Image Sources

Figure 1: Hasan, M. H., Rahman, M. R., Haque, A., & Hossain, T. (2019, January). Soil salinity hazard assessment in Bangladesh coastal zone. In International Conference on Disaster Risk Management.

Figure 2: Habiba, U., Abedin, M. A., Shaw, R., & Hassan, A. W. R. (2014). Salinity-induced livelihood stress in coastal region of Bangladesh. In Water insecurity: A social dilemma. Emerald Group Publishing Limited.

Figure 3: Salehin, M., Chowdhury, M., Arefin, M., Clarke, D., Mondal, S., Nowreen, S., ... & Haque, A. (2018). Mechanisms and drivers of soil salinity in coastal Bangladesh. In Ecosystem services for well-being in deltas (pp. 333-347). Palgrave Macmillan, Cham.

Figure 4: Tajwar, M., Uddin, A., 2022, Hydrochemical Characteristics and Quality Assessment of Groundwater in Hatiya Island, Southern Coastal Region of Bangladesh: Geological Society of America Abstracts with Programs. Vol 54, No. 5, doi: 10.1130/abs/2022AM-38266

Acknowledgement: This material is based upon work supported by the Geological Society of America. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the funding organizations. Mahir is currently a Ph.D. student at Vanderbilt University, having completed his M.Sc. from Auburn university.