Photo taken on Aug. 3, 2011 shows the black clouds over the Gyaring Lake, northwest China's Qinghai Province. The sister lakes Gyaring Lake and Ngoring Lake are two largest freshwater lakes on the main stream of the Yellow River, affecting the function of adjusting water volume. With the progress of environmental protection and development of nature preservation zone of the Three River Sources, the areas of the sister lakes have enlarged each 31.76 square kilometers and 59.46 square kilometers in recent years.[Photo/Xinhua]