Effects of Aila, a severe tropical cyclone on three major hydrological parameters namely surface water salinity, pH and DO in the western part of the deltaic Sundarbans region of Indian sub-continent at the apex of Bay of Bengal is ascribed in the present study. It consists the in situ studies before and during Aila at 12 sampling stations in the Hooghly estuarine complex and also extended our studies further (ten days after the storm hit the Gangetic delta) to visualize the situation of the aquatic phase. There were changes in surface water salinity, pH and dissolved oxygen (DO) due to intrusion of saline water from the Bay of Bengal. Due to this severe cyclonic storm, high energy tidal surges increased the average salinity of surface water from 13.64±6.24 ppt to 17.08±8.03 ppt, which is a rise of 25.2%. Average pH changed from 7.99±0.20 to 8.01±0.21 which is an increase of 25.03%. Average DO decreased from 5.24±0.70 ppm to 4.95±0.51 ppm, which reflects a fall of 5.53% in the area of investigation due to intrusion of sea water. Ten days after the Aila incidence was over, the salinity and DO exhibited gradual restoration. Such drastic changes of hydrological parameters due to natural calamities may pose an adverse impact on the ecology of the deltaic complex and requires a systematic planning to combat the ecological effect of the disaster.