The Lonar Lake of Maharashtra is a crater based-saline lake. During the month of June 2020, this lake suddenly changed its colour and turned to pink due to the presence of Haloarchaea microbes, and this species have a unique adaptation style to survive in high saline condition. The salinity of this lake is increasing due to less rainfall, low human intervention, and an increase in the temperature of this region. These microbes produce fantastic bloom, which can be sensed from outer space because of red-orange carotenoids production. In this work, Sentinel 2A datasets have been used for the duration of January 2020 to June 2020. These datasets have been processed in Google Earth Engine platform and several indices like Salinity Index, Surface Algal Bloom Index, and Normalized Difference Haloarchaea Index have been calculated. With the help of these indices, it has been found that the appearance of these microbes has happened in the early part of June 2020, and in more precise terms, it can be stated that between May 31 and June 5, these microbes have appeared in the lake.
The proper functioning of the river ecosystem has been symbolised by healthy aquatic life. The river Ganga has shown signs of rejuvenation due to lockdown. In this study, an attempt has been made to analyse the change in river water quality using Sentinel-2 and Landsat-8 imageries. The quantitative analysis has been performed for temperature and normalised difference turbidity index (NDTI). The qualitative analysis has been performed for pH, dissolved oxygen (DO) and total suspended solids (TSSs). Ghazipur, Varanasi and Mirzapur stretches have been selected for this study. In the Ghazipur stretch, the river temperature decreased by 7.14% in May 2020 (lockdown period) as compared to May 2019 (1 year before lockdown). Similarly, in the Varanasi stretch, this decrease has been by 8.62%, and in the Mirzapur stretch, this decrease has been by 12.06% in May 2020 compared to May 2019. For the same period, NDTI in the Ghazipur, Varanasi and Mirzapur stretch has been decreased by 0.22, 0.26 and 0.24, respectively. The pH and DO of the river increased, and TSS decreased for the considered time period. The lockdown during the second wave of the coronavirus disease 2019 was not helpful for river rejuvenation. This study elicited how the behaviour of the parameters changed during the lockdown.
Research highlights
River Ganga becomes much cleaner in the lockdown period (May 2020) compared to the pre-lockdown time.
In the Mirzapur stretch, the temperature decreased most in May 2020 as compared to May 2019.
In the Varanasi stretch, there is a maximum variation in the NDTI value in May 2020 in comparison with that of May 2019.
The most significant task will be to maintain river conditions during post-lockdown similar to that prevailed during lockdown.
In the second wave COVID-19 lockdown the river again became polluted like the pre-COVID times.
Excessive water use in the agricultural sector in the Betwa-Dhasan basin of the Bundelkhand region is becoming the cause of irrepressible drawdown in the groundwater level. These changing dynamics are becoming the cause of water scarcity in the basin and increasing difBculty in fulBlling the water demand of the area. For incorporating the water-saving agricultural practices in the region, it is essential to have a precise estimation of the crop water productivity (CWP) and evapotranspiration (ET) at the basin scale. In this analysis, the Kharif and Rabi seasons of 2004-2005, 2009-2010, and 2013-2014 have been included. The ET and CWP have been calculated for all the seasons. The MODIS satellite imageries have been used for calculating the ET using the surface energy balance algorithm for land (SEBAL) algorithm. The highest CWP has been recorded as 2.56 kg/m 3 for the Rabi season 2014. With the increase in the demand for water for irrigation and agricultural purposes, the groundwater gets depleted. The decadal groundwater Cuctuation map of the Rabi season (2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014) shows that groundwater gets depleted by more than 30 m within this period in some of the river basin regions situated in the Jhansi and Tikamgarh districts.
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