Why is the Three Gorges of the Yangtze River also called Xiajiang?

700 miles of the Three Gorges, with mountains on both sides, is completely uninterrupted. Layers of cliffs block the sky and the sun. If it weren't for noon and midnight, the sun and the moon would not be visible. In summer, the sky climbs up the mountain and rises to a high place, and the upstream and downstream waterways are blocked, making it impossible to sail. Sometimes the emperor's name needs to be conveyed quickly. At this time, you can leave Baidicheng in the morning and arrive in Jiangling at night. The distance between the two places is 1200 Li. Even if you ride a horse and ride the wind, it is not as fast as taking a boat. In spring and winter, there are white rapids, green deep pools, and the swaying clear twists and turns shoot out the shadows of various scenery. There are many cypresses with different postures on the extremely high mountain peak. Between the two mountains, there are hanging springs and waterfalls washing down. The water is clear and the trees are glorious, and the mountains are high and the grass is long, which is endless. Every morning after the rain, the frost falls, the Woods are cool and the mountains are silent. There are often apes whistling, and their voices are continuous and sad. They echoed in the empty valley and disappeared for a long time, so the fisherman sang: The Wuxia Gorge of the Three Gorges in Badong is long, and the ape cries three times, and tears spill on his skirt.