Talk:Gangotri Glacier

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I have rated this as a "B" class. It has cited refs, subsections and images detailing the article. Thanks.--MONGO 04:15, 18 July 2007 (UTC)

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"Threatens the water supply for hundreds of millions of people in Northeastern India and Bangladesh"
I would like to add some commentary about the last sentence in the last paragraph, which is: "Unchecked this retreat threatens the water supply for hundreds of millions of people in Northeastern India and Bangladesh".

Here are some pictures from the source of the Ganges at Gangotri: http://static.panoramio.com/photos/original/15309084.jpg

http://upload.wikimedia.org/wikipedia/commons/thumb/e/ed/Gaumukh_Gangotri_glacier.jpg/800px-Gaumukh_Gangotri_glacier.jpg

All I can see is a small stream flowing out of the glacier, and I wonder how can this small stream pose a threat to the water supply for hundreds of millions of people in NE India and Bangladesh. The Ganges is one of the largest rivers on the planet, and most of its waters come from monsoon rain in the wet season, and only a small part of it from melting snow in the Himalayas. For example, there is a place named Cherrapunji very close to the border between India and Bangladesh which has an average yearly rainfall of 11,430 mm (about 450in).

My another problem is with ignoring the very simple fact that ice melt produces meltwater. If a glacier is retreating, it will certainly lead to more meltwater for hundreds of years than the amount of meltwater in the case of non-retreating. If the whole glacier melts away (absolutely unlikely in the near future) there will be still water in the upper-Ganges. A glacier behaves like a stream or a river, flow the accumulated precipication (mostly snow) from the area, a stream will do the same with melted snow. How can it cause a massive water shortage? In fact, you get more meltwater than average when the glacier is in retreat.

According to reliable information (see Naithani et al [2000], p94. http://www.ias.ac.in/currsci/jan102001/87.pdf), the Gangotri glacier is retreating with an average rate of 19m per year. The total length of the glacier is 30.2 kilometers or 30 200 meters. If the retreating is going to continue in the future at current rate, it will take 1589 years for the Gangotri Glacier to melt away completely. But don't forget the word if: maybe it will be retreating faster, or maybe the process will slow down or even reverse...

I would say that Wikipedia should not provide an opportunity for advocating unscientific, alarmist ideas. —Preceding unsigned comment added by 82.144.178.41 (talk) 12:43, 18 May 2009 (UTC)


 * i largely subscribe to that (surprising to appear here but very) insightful statement. --Alexander.stohr (talk) 17:26, 7 February 2010 (UTC)

Retreat is slowing, not accelerating
In the lead section, it is said that:
 * In recent times, it has been pointed out that the retreat of the glacier has quickened significantly.

without citation. Then in the "Retreat of Gangotri Glacier" section, it says:
 * However, over the last 25 years of the 20th century it has retreated more than 850 meters (34 meters per year)[5], and 76 meters between 1996 and 1999 (25 meters per year). [6]

Firstly, 34 m/yr changing to 25m/yr is obviously not a quickening, but the exact opposite, a slowdown, and a considerable one at that (26% reduction.) After time for anyone else to comment, I will correct the lead section to say "slowed significantly" instead of the plainly wrong "quickened significantly." (Another reference, which I discuss below, shows that this slowing has continued even more strongly after 2001 and in fact the retreat is currently almost stopped, and actually stopped in some parts.)

Secondly, it is difficult to see how reference 5 can be discussing the last 25 years of the 20th century when it was published in 1996. In fact, I do not believe this text comes from reference 5 at all, as it seems to be a verbatim quote from reference 6 (which is not peer reviewed, and does not source its statement.) A copy of reference 5 can be obtained at http://webcentral.uc.edu/eProf/media/attachment/eprofmediafile_443.pdf (warning, 2.5 MB PDF) I am still reading through it, but so far I can find nothing to support to the quote; in fact it primarily concerns glaciation 63,000 years ago.

Thirdly, Indian government surveys (e.g discussed in "Himalayan Glaciers: A State-of-Art Review of Glacial Studies, Glacial Retreat and Climate Change", V.K.Raina, Indian Ministry of State for Environment and Forests, 2009) show a highly variable retreat across the width of the snout from 1996 to 2001, with the fastest parts retreating at 25 m/yr (as suggested in reference 6) but many sections doing under 20 and about a third of the face retreating by less than 10 m/yr. While broadly consistent with reference 5, this detailed data make it look very much as though the "sound bite" quotes in reference 5 are cherry-picking the worst data and presenting them as typical. Furthermore, and most importantly of all, the same survey shows the retreat almost stopping after that; from 2001 to 2006, retreat varied across the face of the snout from 50 m to 0 m, with the average being about 20 m, or 4 m/yr. At that rate Gangotri would last for thousands of years -- but it is actually even better than that. You see, the Indian glaciologists' model shows that retreating glaciers are not retreating indefinitely, but asymptotically approaching a new equilibrium line. If the new equilibrium line is higher than the head of the glacier, the glacier will vanish. But Gangotri's new equilibrium line is only a few hundreds of metres behind the current snout. Precisely as the model predicts, observational data shows that the retreat is now rapidly slowing, and may soon practically stop altogether. -- 202.63.39.58 (talk) 11:25, 11 July 2010 (UTC)