One of the largest coastal fresh groundwater zones located in between the Kobadak and Hari rivers in Khulna will disappear by 2050 due to salinity rise in the coastal belt, accelerating a freshwater crisis there, warns a new study. Due to climate change, the study says the increase in vertical salinity distribution between the Kobadak and Hari rivers is distinct by the year 2050. The salinity range will disappear and the aquifer salinity will increase to higher values. The Department of Public Health Engineering (DPHE) and the Institute of Water Modelling (IWM) conducted the study titled, ‘Joint Action Research on Salt Water Intrusion in Groundwater in the Coastal Area’. Starting from September 2010, the study was completed in December 2014.
The JAR project leader M Rezaul Hasan said using mathematical models, the research team has found a big freshwater zone 20-90 meters beneath the surface located in between Kobadak-Hari rivers, but the team predicts that the zone will disappear by 2050 due to increase of salinity caused by sea level rise. The study was carried out in parts of three districts of Khulna, Jessore and Satkhira covering about 1534 square kilometres, aiming to assess salinity extent and intrusion, and aquifer vulnerability in the area.
The study reveals that in the year 2050 for average hydrological condition considering human intervention, the area of freshwater zone (less than 1000 ppm – parts per milligram) will decrease to its present condition. Within the saline zone, the areas of severe salinity (more than 2000 ppm) will go up by 11 percent by 2050 and vertical groundwater salinity distribution along the rivers of Kobadak-Hari will increase substantially. He said the coastal areas have already been facing salinity problems which is predicted to be exacerbated by climate change and sea level rise.
“Much more work is needed to accurately define the freshwater-saline water interface and to monitor its seasonal and long-term movements,” said Rezaul. Coastal aquifers are vital sources of freshwater throughout the world. Bangladesh, especially the low-lying coastal areas, is likely to be in extremely vulnerable condition under the current scenario of changes in climate condition because of its geographic location and low-lying topography. This scenario is likely to be worsened by reduced dry period flow and increased use of water for domestic, industrial, irrigation and other needs.