Seasonal dynamicity of environmental variables and water quality index in the lower stretch of the River Ganga

Abstract Rapid human pressure in semi-urban and urban areas along with increasing industrial activities has resulted release of untreated sewage other forms pollutants into major rivers globally including the Ganga. In this study, nine sites represented by 59 stations lower stretch River Ganga were monitored seasonally to understand effect monsoonal precipitation on environmental variables Water Quality Index (WQI). Sampling was undertaken pre-monsoon, monsoon post-monsoon seasons (2019). situ surface water temperature, dissolved oxygen, pH, total solids (TDS) electrical conductivity (EC) measured nutrients Chlorophyll-a. Both pH DO strongly influenced affected WQI. TDS higher point source (PS) during pre-monsoon (113–538 ppm) compared (SW) (113–248 strong influence (PS-27.4-310.3 ppm; SW-27-68.9 ppm). Dissolved nitrate o -phosphate concentration showed significant seasonal variation precipitation. PS across studied varied from 26.33–646 ? M while SW range 21.22–148.06 M. sites, reflected municipal directly river. The resulting clearly evident biological variable (concentration Chl-a) observed values (0–21 mg l ?1 ) which lesser (0–89.3 monsoon. Non-metric multidimensional scaling revealed three distinct clusters greater overlap between WQI (14–52) determined for very poor quality majority did not have any trends.