Özet:

The river Yamuna is considered a crucial river in the Indo-Gangetic plain. Having 0.4 Percent of the catchment area in the National Capital Territory (NCT) of Delhi, it feeds about 70 per cent of the population of Delhi and hence, is a major source of dependency for NCT of Delhi. The water quality monitoring of River Yamuna is done by the Delhi Pollution Control Committee (DPCC), Delhi on monthly basis.The objective of the study is to investigate the water quality of the river in the Delhi stretch, for the period 2003-2021. The water quality data has been derived from experimental analysis at DPCC across seven monitoring stations and has been analysed in the present study. It has been revealed that pollutant load from urban local bodies and drains have a stronger impact on the water parameters after the Wazirabad in Delhi, resulting in deteriorated water quality and high-Water Quality Indices (WQI). Water Quality Index (WQI) for the year 2021 indicates that pollution in the river Yamuna increases during monsoon and post-monsoonperiods while during pre-monsoon it remains relatively low.The average pH of the river water ranges from 6 to 8 throughout the year. The comparative data reveals that dissolved oxygen (DO) at most of the sites (except Palla) is nil and, the values of BiochemicalOxygen Demand(BOD) and Chemical Oxygen Demand (COD) have been increasing tremendously, which is due to the unregulated discharge or dumping of sewage water from urban local bodies (ULB) in the river.

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