Effects of COVID-19 lockdown on hydrochemical properties of the Brahmaputra River, India

AbstractMillions of the people in Assam- India, rely on the Brahmaputra River for survival. Hence, the assessment of the suitability of its water for drinking and agricultural use is of utmost necessity. The present research work assessed the water quality of the Brahmaputra River before and after the COVID-19 lockdown period. Eleven sampling stations along the river's course were analysed. The trend of cations and anions was observed as Ca2+> Mg2+> Na+>K+and HCO3−> SO42−> Cl−> NO3−> PO43−, both before and after the lockdown. Statistical analysis showed more deteriorated water quality after the lockdown. Chemical oxygen demand (COD) during post lockdown period was 1.4 times higher than the pre-lockdown, signifying more pollution in the post-lockdown period. Silicate and carbonate weathering was found in both periods. The drinking water quality did not improve after the lockdown and remained 'poor' for both periods. Indices used to analyse irrigation water quality were percent Sodium (Na%), Magnesium hazard (MH), Sodium Adsorption Ratio (SAR) Kelly's ratio (KR), Permeability index (PI) and Cation ratio of soil structural stability (CROSS). SAR index and Wilcox diagram depicted deteriorated water quality after the lockdown period, making it harmful for irrigation.