(170904) --YAN'AN, Sept. 4, 2017 (Xinhua) -- People visit the Hukou Waterfall on the Yellow River on the border area between north China's Shanxi and northwest China's Shaanxi provinces, Sept. 4, 2017. Due to heavy rainfall at the upper reaches, the water volume of Hukou Waterfall surged. (Xinhua/Tao Ming) (yxb)