Assessment of spatio-seasonal variability of key physicochemical parameters in the Yamuna River

The Yamuna River is a vital freshwater resource in northern India, yet it experiences severe pollution pressures, particularly along its urbanized stretches. This study evaluates the spatio-seasonal variability of major physicochemical parameters temperature, pH, dissolved oxygen (DO), salinity, turbidity, electrical conductivity (EC), free CO₂, bicarbonate, calcium, magnesium, nitrate, nitrite, chloride, and total ammonia across three monitoring stations: Tajewala, Wazirabad, and Okhla barrages. The findings reveal clear spatial degradation from upstream to downstream, accompanied by notable seasonal fluctuations. Temperature increased from 17.80-26.36°C at Tajewala to 22.17-31.60°C at Okhla, while pH varied between 7.26 and 8.55 across sites and seasons. DO concentrations declined critically downstream, from 7.63-8.15 mg/L at Tajewala to 3.27-3.63 mg/L at Okhla, indicating severe organic loading. Turbidity and EC showed substantial downstream elevation, peaking at 383.03 mg/L and 1,393.75 µS/cm, respectively, reflecting high sediment and ionic influx. Major ions also increased notably downstream, with bicarbonate (113.75-293.50 mg/L), calcium (39.37-242.12 mg/L), and magnesium (104.25-361.00 mg/L) showing distinct enrichment. Nutrient pollution was most pronounced at Okhla, where total ammonia reached 12.55-13.30 mg/L, far exceeding ecologically safe limits. Nitrate (0.075-0.188 mg/L) and nitrite (0.320-1.830 mg/L) also displayed rising trends downstream. These patterns indicate strong anthropogenic influence, especially from sewage discharge, industrial effluents, and urban runoff.