Water quality indices to assess the spatiotemporal variations of Dhaleshwari river in central Bangladesh

Different water quality indices were determined to assess the spatiotemporal variations of Dhaleshwari river, specially, where effluent from the central effluent treatment plant (CETP) of newly shifted tannery industrial park was discharged. Thirty physicochemical parameters were examined to evaluate the drinking water quality index (DWQI), irrigation water quality index (IWQI), heavy metal pollution index (HPI) and contamination index (Cd). Pearson’s correlation coefficient was also utilized to understand the interrelationship and coherence pattern among the parameters and indices. DWQI values using CCME method were within the ‘Poor’ (0–44) range (37 ​at both upstream and junction and 34 ​at the downstream) and those using W.A. method were at ‘Poor’ (51–75) and ‘Unsuitable’ ( ​> ​100) level (52 ​at upstream and 63 ​at downstream and 103 ​at the junction). IWQI values showed the ‘Excellent’ (0–25) quality status (a range of 19.2–20.3). Considering heavy metal pollution, HPI values revealed ‘Critical’ ( ​> ​100) condition of water, and Cd values ( ​> ​3) emphasized ‘High’ contamination of the river water. Temporally, water quality deteriorated in the winter season compared to the monsoon and post-monsoon season. Spatial changes in water quality in junction and downstream side clearly indicated the negative impact of tannery industrial park. Different indices were positively correlated either very strongly or strongly. This study will provide an index-based baseline data that will help the local people in the vicinity of tannery industrial park envisage the different applications of the river water and the policymakers take conservation strategies to save the river Dhaleshwari as well.