Nothing magical about glacier water.
Your car overheated because water level was low in radiator. When you topped it up. It didn't overheat. The reason the temp stayed below 50% is probably because you have removed the thermostat valve or it has stopped working. Thus water flows freely through radiator and because temperature in Naran is much more colder, the air coming through the radiator fins, was enough to keep the temp below 50%.
When you came back from Naran, obviously the temp was much higher, hence the air coming through the radiator was not so cold, hence the temp goes up to 50% after which the automatic fan kicks in and keeps the temp at 50%. So my conclusion is that you need a new thermostat valve.
Some time back, a similar problem happened with my Civic. In winter season on the highway, the temperature would drop below 50%. Reason was that the thermostat valve would not close, hence water was flowing freely through the radiator and the cold air would keep the temp below 50%. But in city driving, the temp stayed at 50% all the time. I replaced the valve and problem solved. Temp stays at 50% all the time