Monitoring of water Quality to assess Seasonal Color Changes of Lunar-Lubha River in East Jaintia Hills, Meghalaya (India)

Abstract

The Lunar-Lubha River is a significant river in Meghalaya, India, flowing through the Jaintia Hills and eventually reaching Bangladesh’s Surma valley. During winter, the river undergoes a remarkable transformation, changing its color from turquoise to a vibrant sky-blue hue. This study investigated the reason behind this color change by examining the physicochemical characteristics of the river water during pre-monsoon, post monsoon and winter season of the year 2020 to 2022. Chemical properties of the white-powdery sediment (which acts as light reflecting media) found on the riverbed of the color-changing stretches of the river were also investigated. The analysis revealed the presence of high levels of Iron (Fe) and Alumina (Al) in sediments of the Lunar-Lubha River beds. The water quality in stations located at Lunar River can be designated below-E as per Central Pollution Control Board (Govt. of India) guidelines as the water in those stations is not fit for drinking, bathing, propagation of marine life as well as irrigation or agricultural uses. The blue coloration is more prominent in the deeper sections of the river compared to the shallow stretches. This observation aligns with the argument that shorter wavelengths of light scatter more as the depth increases. The presence of light scattering effect due to variation in water depth and the white-colored sediments at the riverbed could explain the intensified blue color in the river. The apparent blue color of the Lukha River is most likely an illusion induced by the scattering effect rather than the genuine blue color of the water.