Gradients of salinity in water sources of Batiaghata, Dacope and Koyra Upazila of coastal Khulna district, Bangladesh

Salinity intrusion affects the soils and water for irrigation and drinking purpose severely in coastal Khulna District. Therefore, current research was done to find out the salinity gradients in different sources of surface water e.g.- river water, canal water, pond water, together with deep tube well water of Southern parts of Khulna District. Previously, these sources were used for irrigation and drinking purposes. Water samples were collected from selected Unions of Batiaghata, Dacope and Koyra Upazila of Khulna District, because these Upzilas were situated in the Southern parts and near to the Bay of Bengal. A total of 51water samples were collected to determine the physical and chemical parameters e.g.- turbidity, electrical conductivity, pH, total dissolved solids, salinity and the concentrations of iron (Fe), sulfate (SO42−), phosphate (PO43−), sodium (Na), potassium (K), calcium (Ca) and magnesium (Mg). The results showed that in most of the cases, the concentrations of the mentioned parameters were very high in the water sources as compared to the standard value set by Bangladesh Bureau of Statics and World Health Organization. In Koyra, the salinity levels were 9500 mg L−1 in river water, 8535 mg L−1 in canal water, 2541 mg L−1 in deep tube well water and 1560 was in pond water. Similarly, in the case of canal water the salinity values were 8535 mg L−1 in Koyra, 7075 mg L−1 in Dacope and 4180 mg L−1 was in Batiaghata. It was found that the salinity was the highest in Koyra and was the lowest in Batiaghata, indicating that salinity increased from North to the South direction. This is because the Southern part is very near to the Bay of Bengal. Among the sources, river water contained the highest salinity and pond water contained the lowest. Salinity trend could be ranked as river water ≥ canal water ≥ deep tube well water ≥ pond water. Current study will be very effective to know the present scenario of salinity and to find out further effective solution in the coastal Khulna region of Bangladesh.