Gangkar Puensum and Three Rivers.

In the past, the farmers of Bumthang were envious of those living in the valley of Mangde and Kurtoe because those two valleys besides having many hilly terrains, they managed to built beautiful terraces and grow paddy. But the poor Bumthaps, despite having a beautiful valley with nearly plain topography, they could not grow paddy which is why they mainly feed on the cuisines made from flour made from wheat, buckwheat, barley etc.., but the reason is obvious as the legends says as follows:

Gankar Puensum: google images

Long ago at Gangkar Puensum, literarily meaning “White Peak of the Three Spiritual Brothers ", (the Highest Mountain in Bhutan @ 7561 m), three lakes were also blessed beneath each brothers from almighty. The lakes being the blessing from above have more roles to play for the wellbeing of the sentient beings so the three brothers planned what they have to do for the dwellers in Drukyul.

 

One evening the three brother peaks, after gazing down towards the lush valleys of Bhutan, they unanimously decided to flow as three rivers from the three lakes to drain the valley and turn them fertile so that the dwellers can have a bountiful reap annually. But a conflict arose among the three brothers while they were discussing about the path they were to follow. The three brothers could not conclude on following the same track, as this would mean lesser credit for the ones that flow latter.

Calm Chamkhar Chhu : google

So the three before going to sleep that evening came to an agreement that they will take their own route the following morning and compete a race. They also agreed that they will meet at a common point after draining the valleys and the condition was that the valleys drained by the first and second rivers would reap paddy, the main staple food of Bhutan while the valley drained by the third river will reap only the common cereals and not rice. The term was agreeable to all the three brothers. However, none of the three mentioned about the timing at which the race should began.

The next morning, before the dawn cracked the eldest brother was awake. Instead of awakening his two little brothers, he silently woke up and flowed down the mountains to enter the valley of Drukyul. Fearing that his noise would awake the two other brothers, he selected the most comfortable routes and flowed slowly without making much noise. But his speed being slow he could not reach the destination at the earliest despite taking the plain through the valley Bumthang. This is also one reason why Chamkhar Chhu flow without making much noise.

Mangde Chhu : google

When the second eldest brother was awake, he found that their eldest brother has already left. So not knowing how far his brother has reached down the valley, he also started flowing down taking the comfortable routes at a faster speed with little splashes. He was also so mean to awake his little brother. He then penetrated through the valley of Trongsa. It is said that Mangde Chhu flow swifter and much noisier than Chamkhar Chhu.

When the youngest brother was awake, it was already late in the morning but when he turned around to awaken his two brothers, he found both of them gone. Therefore, without thinking much about the trials and tribulations he would encounter, he started his journey with high speed and started flowing through any type of terrain so fiercely be it jungles or cliffs. The river ferociously and noisily drained the valley of Lhuentse and it is known as Kuri Chhu.

Kuri Chhu : google

When Chamkhar Chhu finally finished its route through the plains of Bumthang, with great relieve it flowed down thinking that he is the first to complete the race but then he found the trails of Drangme Chhu before him. There was nothing he could do then join his brother for the journey ahead. Thus, Chamkhar Chhu lost to Mangde Chhu in the race. Mangde Chhu was relieved that at least he could bless the valley he has drained with paddy. The two brothers then turbulently flowed downwards only to discover that their youngest brother has already gone ahead of them. After catching the youngest brother, the three siblings however joyously proceeded their journey forming the mighty Manas through the Indian plains to reach the oceans.

This is how the youngest brother won the race followed by second brother and this is the rationale why Bumthng valley does not grow rice despite having fertile plain valleys. The two valleys of Trongsa and Lhuentse grow paddy. The unity among the Bhutanese can also related to the fact that the three rivers flowed further together all in one forgetting about who won and who lost the race.

But no worry, global warming has already helped Bumthang grow paddy.  The sad thing is that the peak of Gangkar Puensum is prone to wither day by day unless precautionary measures are taken before hand by the dwellers, who are reaping the blessings of Gangkar Puensum one way or the other.

Another myth says that when these three rivers (Kuri Chhu, Chamkhar Chhu, and the Mangde Chhu) made their first descent from the glacial lakes of Gangkar Puensum, they proposed to have a race. While the other two rivers entered into the race the Chamkhar Chhu showed lack of interest in such a race and asked the other two to go ahead, saying that he would follow them at his own leisurely pace.  This is the reason why the Bumthang Valley is being blessed with a wide and calm expanse, while the Trongsa and Lhuentse Valleys are steep and narrow. 

P.S: This is a folklore, which I heard some ten years ago so it might contain some mistakes, or I might have told from a different angle. Kindly bear with it and share with us if you have any similar myths about this content of the story. 
Besides Gangkar Puensum is also a commonly used simile in Bhutanese songs be it traditional folk or modern lyrics. See more in the succeeding posts.