Dry valley of Jinsha River

A dry valley in the Hengduan Mountains region, SW, China, and an artificial reservoir (the Ahai Reservoir) is impounded on the mainstream of the Jinsha River, the source water of the Yangtze River. The valley is dry and warm during the dry season (Nov. to May) and humid and hot during the wet (Jun. to Oct.). Annual precipitation in the picture is less than 600 mm, which results in that some slopes are totally covered by cactuses (both banks in the picture). Such a special climate only exists below certain heights in deep valley (generally 500 m above the river surface). Above these heights, climates belong to latitudinal climatic zone that's the wet SW China commonly seen. Therefore, the higher elevation above the bottom of the dry valleys, the more vegetation covered, which is contrary to the vertical distribution of vegetation commonly spread in the Hengduan Mountains region. In the picture, the water surface is at 1420 m a.s.l, and the top of the mountain of each bank is more than 3200 m a.s.l.