The current study analyses a seasonal change in various physicochemical
parameters of Varuna River at Varanasi during pre-monsoon, monsoon and post-monsoon seasons. Important parameters are pH, dissolved oxygen
(DO), biochemical oxygen demand (BOD), chemical oxygen demand(COD), turbidity, and total dissolved solids (TDS) were studied to assess
changes in water quality over time under different hydrological conditions.
The results indicate different seasonal trends which were predominantly
controlled by monsoonal rains, surface runoffs, dilution processes, and the incessant anthropogenic contributions. The high value of BOD and COD in
the pre-monsoon season suggests that organic pollution burden is much
higher in the low-flow environment in the pre-monsoon period than in the
high-flow period as indicated by higher turbidity of the water in the season.
The increase in the dissolved oxygen during monsoon and post monsoon
implies that recovery was partial, as more flow and natural aeration
occurred. Altogether, the identified seasonal changes demonstrate a joint
effect of natural activities and human actions on the water quality of the
Varuna River, which makes it necessary to monitor the situation in the river
seasonally and implement effective methods of pollution control.