In Tibetan Plateau, about 4600m elevation, If Lake Manasarovar and Lake Rakshastal ("lake of the demon" ) used to be the same lake, but due to the tectonic activity now they are separated to two by small hills, how come Lake Manasarovar is a fresh-water lake while Lake Rakshastal is a salt-water lake?

Before they were separated, was the overall old lake a fresh-water lake or a salt-water lake?

enter image description here

Is that just because Lake Rakshastal is in the Endorheic basin and Lake Manasarovar is not within the Endorheic basin?

Also, Lake Manasarovar overflows into lake Rakshastal which is a salt-water endorheic lake. These lakes used to be part of the Sutlej basin and were separated due to tectonic activity.

  • $\begingroup$ Seems obvious: Manasarovar overflows into Rakshasta, so its water is being continually replaced with fresh water. $\endgroup$ – jamesqf Mar 28 '17 at 18:15

You pretty much answered the question yourself. Lake Rakshastal, along with most of the lakes along the Tibetan plateau is, indeed an endorheic lake. The important meaning of that term is that there is no outflow from that basin. Water evaporates, but as with any evaporative process, the minerals in the water stay behind and become more concentrated. Since Lake Manasrovar flows into Lake Rakshastal, the water that leaves takes the minerals in contains with it, leading to a much lesser concentration left behind as new water flows in, and, most importantly, out of that lake.

  • $\begingroup$ Thanks, question i) Now Lake Manasarovar is a fresh-water, will it become a salt-water lake, say in what time scale? $\endgroup$ – wonderich Mar 29 '17 at 0:00
  • $\begingroup$ Appreciate your answer. question ii) Before the two lakes were separated, was the overall old lake a fresh-water lake or a salt-water lake? (Perhaps it depends on the ratio of water volume of two lakes? Also the definition of fresh or salt? Comapring to the human standard.) $\endgroup$ – wonderich Mar 29 '17 at 0:01
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    $\begingroup$ @wonderich: Assuming that there is enough inflow to produce a regular outflow, it will never become significantly saline. As to what the original lake was, we can't really say without more information. If it was landlocked for a significant period, it would become saline. If it had regular outflow to some other basin, it would not. (At least with sufficient outflow to replace saline water before significant accumulation took place.) $\endgroup$ – jamesqf Mar 29 '17 at 4:00

I feel that before tectonic plate movement Kali Gandaki was flowing northword in Tethys ocean which got separated in the form of Mansarovar sweet water of river, whereas Rakastal is pushed up waters of Tethys ocean which has to be salty.enter image description here

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    $\begingroup$ Welcome to Earth Science SE! As a science site, we generally prefer answers backed with references than "feelings". $\endgroup$ – Jean-Marie Prival Mar 15 '20 at 11:05
  • $\begingroup$ As I trekked in the area I could see the relevance . However whatever has happened during Himalaya formation has to start with some assumption. You can delete my answer as I am not any scientist or research Geologist. $\endgroup$ – Aditya Paranjape Mar 21 '20 at 5:09

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