Impact of Climate Change and Ganges Discharge on the Salinity of the Passur River, Southwestern Bangladesh

Abstract

The present paper embodies the possible impact of climate change and upstream discharge on the Passur River water at the Mongla point of Khulna division, south-western part of Bangladesh. The secondary data have been gathered from different sources and were analysed to understand the aforementioned situation. To establish the relationship, the long-term salinity data (1962-2015) have been taken into account as the dependent variable with other climatic variables’ viz., temperature, rainfall, river discharge, tide level and also sea level change. The salinity of the Passur River increased persistently at a rate of 0.13 ppt/year from 1962 to 2015. Dramatic changes of salinity have been audited after the construction of Farakka barrage (1975), which apparently increased from 0.35 ppt to 7.05 ppt in 2015. A continuously increasing relation has been observed in salinity with both the temperature and the position of sea level. Notwithstanding the inconsistency of rainfall data, an inverse relation was also noticed between salinity and rainfall, i.e., salinity increases with the decrease in rainfall. The relation between freshwater discharge at the Hardinge Bridge Point of the Ganges River and subsequent salinity in the Passur River has been compared establishing that the long-term gradual and abrupt decrease in discharge has a direct impact on the increasing trend of the salinity of this River. On the basis of foregoing results and observations, an attempt has been made to generate an equation that may predict the future scenarios of the salinity, temperature and sea level changes for 2050. Nevertheless, a minor disparity in the data of various parameters, it may be concluded that the salinity, temperature and the sea level will be increased significantly in the near future. From the present findings, an immediate measure has to be taken to overcome the possible adverse impacts of the inevitable climate change.