2-Source of river

(1) Atmospheric precipitation -main source of river: after the rainwater falls on the surface, some evaporates and returns to the atmosphere, some is absorbed by plants, some is permeated into the soil pore space or rock crevice and becomes the underground water, the remaining part runs along the surface, runs through rivers and finally enters into the sea.
(2) Underground water: karst area, underground water runs out of the surface and feeds into the river.
(3) Ice and snow: in the areas with high mountains and high latitude, snow melts into the water and feeds into the river.