Seasonal and Spatial Variation of DO and BOD for Assessment of the Water Quality of Brahmaputra River

In this study, an attempt has been made to monitor the water quality of the Brahmaputra river by analysing two major parameters, viz., DO and BOD by plotting various curves to determine the seasonal as well as the spatially variation of the parameters along the river stretch. The seasonal variation of DO in the Upper Assam region showed similar trends for the pre- and the post-monsoon period with a decreasing trend as the river flows from Kherghat to Dibrugarh and thereafter shows an increase of DO levels near Dhenuka paharh. A decreasing trend was again observed as the river passes through the Nimatighat region. Similarly, for the monsoon season the variation of DO showed an increasing trend as it passes through Dibrugarh and as the river progresses towards the downstream, discharges from various cities along the river stretch blend with the river water, thereby increasing its pollution levels and hence a decreasing trend was observed for the DO in the downstream portion of the Upper Assam region. As far as the variation of BOD along the river stretch is concerned, it was observed that it varies inversely as the DO, which can be seen as an appropriate co-relationship between the two parameters. Similarly, variations of the BOD and DO were obtained for the Lower Assam region. The spatial variation of the BOD and DO showed the map of the depicting the variation of the parameters along the entire river stretch. Proper visualisation of the maps obtained would thereby help in predicting the stretch most polluted so that proper river training works can be done to restore the water quality in the river.