Alaknanda colour changed
Source: By Lalmani Verma: The Indian Express
The Alaknanda rises in the Satopanth glacier and is met at Vishnuprayag by the Dhauli Ganga, which carried deposits from the flood on 7 Feb 2021. The Alaknanda is then met by the Nandakini at Nandaprayag, Pindar at Karnaprayag, Mandakini at Rudraprayag, and Bhagirathi at Devprayag. Thereafter, it is known as Ganga, which flows to Rishikesh and Haridwar.
The pictures below show the Alaknanda at Devprayag, muddied by the landslide and flash flood in the Rishi Ganga and Dhauli Ganga on 7 February 2021. The muddiness, which persisted, is the result of suspended sand, clay, rocks, in the water, geologists and environment scientists in Uttarakhand said.
The river is usually clear in winter, Uttarakhand Pollution Control Board (UPCB) environment engineer Ankur Kansal said; it becomes muddy only in the monsoon. Kansal could not recall when the Alaknanda had been seen this muddy in winter. The flood weakened downstream of Tapovan, and the mud and debris reached Rishikesh on 11 February 2021, travelling 250 km in three days. UPCB data show the Ganga was clean at Rishikesh and Haridwar on 6 February 2021; it was classified as “muddy” on 11 February 2021, and is currently “turbid”.
The volume of debris that fell into the Rishi Ganga and was carried downstream to the Alaknanda is difficult to estimate, Dr Kalachand Sain, Director, Wadia Institute of Himalayan Geology, said. But it is estimated that a glacial rock mass of 0.2 to 0.4 million cubic metre volume fell from about 5,600 m to 3,600 m along a 40-degree incline, transforming into a muddy slurry as it picked up vegetation and loose rock along the way, Dr Sain said. Prof Y P Sundriyal of the Hemvati Nandan Bahuguna Garhwal University in Srinagar said no timeframe can be given for the water to flow clear again.
