The novel coronavirus disease (COVID-19) halted almost all the industrial scale anthropogenic activities across the globe, resulting in improvements in water and air quality of megacities. Here, using Sentinel-2A data, we quantified impact of COVID-19 lockdown on the water quality parameters in one of the largest perennial creeks i.e., the Buddha Nala located in District Ludhiana in India. This creek has long been considered as a dumping ground for industrial wastes and has resulted in surface and ground water pollution in the entire lower Indus Basin. Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Normalized Difference Chlorophyll Index (NDCI), Nitrogen Content Index (NI), Normalized Difference Turbidity Index (NDTI), and Total Suspended Matter (TSM) were compared prior (2019) and during (2020) lockdown in the creek. There was a significant enhancement in NDVI, NDWI, NDCI, and NI values, and reduction in NDTI and TSM values during the lockdown period. When compared with prior year (2019), the values of indices suggested an improvement in water quality and an indicative change in aquatic ecology in the creek. The impact of the COVID-19 lockdown on the improvement in water quality of Buddha Nala was more evident in the upstream and downstream sections than the middle section. This is intriguing since the middle section of the creek was continually impacted by domestic household effluents. The earth observation inspired methodology employed and findings are testament to the discriminatory power to employ remote sensing data and to develop protocols to monitor water quality in regions where routine surveillance of water remains cost prohibitive.

中文翻译：

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基于地球观测的COVID-19锁定对印度旁遮普邦佛那拉地表水水质的影响评估

新型冠状病毒病（COVID-19）阻止了全球几乎所有工业规模的人为活动，从而改善了大城市的水和空气质量。在这里，使用Sentinel-2A数据，我们量化了COVID-19锁定对最大的多年生小河之一，即印度卢迪亚纳州的佛陀纳拉水质参数的影响。长期以来，这条小河一直被视为工业废料的倾倒场，并导致整个印度河下游盆地的地表水和地下水受到污染。归一化植被指数（NDVI），归一化水分指数（NDWI），归一化叶绿素指数（NDCI），氮含量指数（NI），归一化浊度指数（NDTI），在小河锁定之前（2019）和锁定期间（2020）比较了总悬浮物（TSM）和总悬浮物（TSM）。在锁定期间，NDVI，NDWI，NDCI和NI值显着提高，NDTI和TSM值降低。与上一年度（2019）相比，该指数的值表明水质有所改善，并且溪流水生生态系统发生指示性变化。COVID-19锁定对佛陀纳拉水质改善的影响在上游和下游部分比中部更为明显。这很有趣，因为小河的中段一直受到家庭生活污水的影响。