Meghalaya in the northeast of India is richly endowed with natural resources such as streams and rivers as well as mineral resources such as coal, limestone, clay, sillimanite, uranium, and more. The estimated coal reserve in Meghalaya is around 576.48 million tonnes while limestone reserves are around 15,100 million tonnes. Exploitation of coal and limestone has been taking place on a large scale in the state.
This paper Seasonal Variation in Water Quality of Lukha River, Meghalaya, India published in the journal Current World Environment informs that this exploitation of coal and limestone has been leading to severe environmental degradation in the state. A number of studies done on the impact of coal and limestone mining have found that mining has adversely affected the water quality of the water bodies in the state besides having an adverse impact on the plant and animal diversity, forest cover, agricultural productivity, etc.
Mining and Lukha’s water
The paper presents the findings of a study that looked at the impact of mining on the water quality of the Lukha river. The Lukha is located in the southern part of east Jaintia Hills of Meghalaya. It receives water from the Lunar river (Wah Lunar) and small streams draining from the Narpuh Reserve Forest and the undulating hills of the area while flowing down. The river is mainly fed by monsoon rain and flows in the south-west direction and later takes a southern path after joining the Lunar river near the Khaddum village. The river passes via the Sonapur village and then into the Surma valley and ultimately ends up in the flood plains of Bangladesh.
Physico-chemical parameters such as the acidity of the water, electrical conductivity, turbidity, total solids, total hardness, calcium, magnesium, chloride, sulphate, phosphate, nitrate concentrations, dissolved oxygen (DO) and biological oxygen demand (BOD) were analysed from four locations of the Lukha.
Findings of the study
The overall water quality of the river was found to be poor and this was attributed to the activities such as mining of limestone and manufacturing of cement in the catchment area of the river. It was found that the pollution of the Lukha river was mainly due to high pollution of the Lunar river upstream that joined the Lukha near the Sonapur village. The water of the upstream Lunar river was found to be highly acidic, with high turbidity levels, high electrical conductivity, high concentration of total hardness, calcium and sulphate in water due to pollution from limestone and cement industries.
The studies by the Meghalaya Pollution Control Board (MPCB) in 2008 have also found that the Lukha gets polluted due to its tributary, the Lunar which comes into direct contact with the mixed coal and leachates and effluents from the limestone mines. This cocktail of contaminants is so deadly that it not only kills the fish and other life forms of the Lunar river, but also those of the Lukha [1].
Locals in the area have observed a change in the colour of the water of the Lukha river over the last seven to eight years during the winter months, which is distinctly visible near the Sonapur village. The water in the river turns deep blue during the months of December, January and February and stays so till the monsoon when high rainfall dilutes the pollutants.
Many NGOs from the region have alleged that the reason behind the river turning blue is the cement factories since coal mining has been banned in the state for nearly two years [1, 2, 3]. But , no evidence has been found to claim it.
This study explored the phenomenon further and found that a few kilometres upstream of the Sonapur village, at the confluence site of the two rivers, the water of the Lunar river is yellowish green in colour due to the presence of thick yellowish powdery and slimy sediments deposited in the river bed by the industrial pollutants. Though the water of the Lukha appears clear, the pollution due to acid mine drainage (AMD) from coal mining areas and powdery sediments originating from the cement plants cause precipitation of aluminium and such other compounds in the water upon mixing of the two rivers. This is found to generate the blue colour in the water.
However, this study has not found any clear relation between the change in the colour and the physicochemical properties of the river water. Neither has any study found the agent responsible for the coloration. The paper ends by saying that there is a need to explore this phenomenon and take urgent steps to prevent further pollution and deterioration of the river.
References:
1. Jesudasan, Goswami (2012) Mined to death: An elegy for the rivers of Meghalaya. Down to Earth. Accessed on 24th September 2016.
2. Dailyhunt (2016) Cement companies responsible for change of colour of Lukha River: HY. Accesssed on 24th September 2016.
3. India Today (2015) Two rivers turn blue in Meghalaya; high acid content doubted. Accesssed on 24th September 2016.