The Heihe River Basin is located at the climatic intersection between
the Westerlies and the East Asian summer monsoon. The highest air
temperature in summer can reach about 40 °C in the plains and downstream
areas, while the lowest air temperature in winter falls to about
−40 °C in the high mountain upper basin area. The upper reaches are
in the Qilian Mountains, in which the source of the Heihe River is located,
and which are characterized by a humid, cold climate with an elevation
between 2000 and 5500 m, and a mean annual precipitation from
250 to 500 mm. Below the snow line (about 4200 m). The vegetation
can be divided into high mountain meadow, brush and meadow, mountain
grass and forest (mainly Picea crassifolia), mountain grass and finally
desert grass in the north. The upstream flow provides water supply
for agricultural production and ecosystem stabilization in the middle
and lower reaches of the basin