Why is Tianshui in Gansu called Tianshui? What's the story?

Tianshui", is the longest-used place name in local history. It was first used in the third year of the Yuan Ding reign of Emperor Wu of the Han Dynasty (114 years ago). The name Tianshui originated from the beautiful legend of "Tianhe River Filling with Water". More than three thousand years ago, the Tianshui area was densely populated, with adjoining houses, "beautiful landscapes and dense forests". However, at the end of the Qin and the beginning of the Han Dynasty, the long-term war, fighting, coupled with successive years of drought, so that when the prosperous, rich city of Shangcheng has become a debris, the people do not want to live. Legend has it that one night, just as people were entering dreamland, suddenly the sky howling winds, thunder and lightning, with a golden light flashing, the ground now red light. At once, the earth continuous vibration, in the rumbling sound, the ground cracked open a big seam. Just see the sky river water pouring down, into the crack in the slit, so the formation of a lake, Tianshui Lake ". This lake level is stable, pure water, sweet and mellow, "spring does not dry up, summer does not overflow, limpid in all seasons". At that time, people said that the lake and the heavenly river, and called it "Tianshui well". Later, this legend was heard by Emperor Wu of Han Dynasty, who ordered to build a new county next to the lake in the northern city of Shangji, and named it "Tianshui County". From then on, the name "Tianshui".