According to World Health Organisation (WHO) and Department of Public Health and Engineering (DPHE) Bangladesh, freshwater is water that contains 300 milligram/litre chloride or less. Water within the range of 300-600 milligram/litre chloride is drinkable.
This latest study, Distribution of Groundwater Salinity and its Seasonal Variability in the Coastal Aquifers of Bengal Delta, found groundwater salinity to be much higher than the potability level in most areas in the country’s coastal districts.
The study was conducted by Bangladesh Water Development Board (WDB) funded by the Bangladesh Climate Change Trust Fund (BCCTF).
WDB Groundwater Circle Deputy Director Anwar Zahid, who led the study, said salinity level beyond potability was found in the aquifers of Shariatpur, Chandpur, Feni, Lakshmipur, Noakhali, Cox’s Bazar, Barguna, Barisal, Bhola, Pirojpur and Jhalakathi.
In most coastal areas, the study found, the level of salinity (Chloride count) in the main or second aquifer ranges from 103 to 12,433 in the dry season and 34 to 11,366 in rainy season.
The highest level of salinity in the main aquifer was found in Patharghata area of Barguna, which is 12,433 chloride count in the dry season and 11,366 chloride count in the wet season.
In case of the third or deep aquifer, the study shows groundwater chloride values between 77 and 12,333 in dry season and 24 and 3,346 in wet season.
Also Read- Fresh water for a price
The highest salinity of 12,333 chloride count was observed in dry season at Kalapara, Patuakhali and a maximum value of 3,346 in the wet or rainy season was observed at Bandaria, Pirojpur.
However, the study found the presence of potable levels of salinity in groundwater at different depth levels of coastal aquifers in Patuakhali, Barisal, Satkhira, Jessore and Narail while brackish water (saline level between 300-600) found at Shariatpur, Chandpur and Gopalganj areas.
However, the study also found Fresh water in the main aquifers at some pocket areas-of Chandpur, Feni, Lakshmipur, Cox’s Bazar, Barguna, Patuakhali, Barisal, Bhola, Satkhira and Jessore district areas.
In the deep aquifer, fresh water occurs in Chandpur, Feni, Laksmipur, Chittagong, Cox’s Bazar, Barguna, Patuakhali, Barisal, Bhola, Satkhira, Jessore, and Narail districts.
It also found the salinity occurs in the deep aquifers of Shariatpur, Barguna, Gopalganj, Khulna and Cox’s Bazar district areas.
The coastal area covers about 20% of Bangladesh and over 30% of the net cultivable area under 19 southern Districts.
Freshwater resources, especially aquifers, are always considered valuable assets in the coastal zone where the surface water is saline most of the year.
Salinity intrusion in Bangladesh coast varies seasonally. In the rainy season (June-October) intrusion of saline water is minimum due to extreme flow of freshwater, but in the dry season, especially in winter, saline water goes upward gradually.
Most of the 19 coastal districts are facing salinity problems. Furthermore, it is anticipated that climate change would have increasing negative impacts on availability of freshwater resources.