Photo taken on Sept. 2, 2014 shows the reflection of the sky over the surface of the lake of Gahai in Luqu County of Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. The Gahai Wetland, a source area of China's Yellow River, is growing in both water area and waterfowl numbers since the establishment of a national natural reserve in 2002. (Xinhua/Xue Dongmei)

Photo taken with a cellphone through a telescope on Sept. 2, 2014 shows two cormorants resting on the lake of Gahai in Luqu County of Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. The Gahai Wetland, a source area of China's Yellow River, is growing in both water area and waterfowl numbers since the establishment of a national natural reserve in 2002. (Xinhua/Zhang Meng)

Photo taken on Sept. 2, 2014 shows the scenery of the lake of Gahai in Luqu County of Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. The Gahai Wetland, a source area of China's Yellow River, is growing in both water area and waterfowl numbers since the establishment of a national natural reserve in 2002. (Xinhua/Li Mangmang)

Photo taken with a cellphone on Sept. 2, 2014 shows the scenery of the lake of Gahai in Luqu County of Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. The Gahai Wetland, a source area of China's Yellow River, is growing in both water area and waterfowl numbers since the establishment of a national natural reserve in 2002. (Xinhua/Xue Dongmei)

Photo taken on Sept. 2, 2014 shows the scenery of the lake of Gahai in Luqu County of Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. The Gahai Wetland, a source area of China's Yellow River, is growing in both water area and waterfowl numbers since the establishment of a national natural reserve in 2002. (Xinhua/Zhang Meng)

Photo taken on Sept. 2, 2014 shows a bird flies over the lake of Gahai in Luqu County of Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. The Gahai Wetland, a source area of China's Yellow River, is growing in both water area and waterfowl numbers since the establishment of a national natural reserve in 2002. (Xinhua/Zhang Meng)

Photo taken on Sept. 2, 2014 shows a staff member observes waterfowls through a telescope at the lake of Gahai in Luqu County of Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. The Gahai Wetland, a source area of China's Yellow River, is growing in both water area and waterfowl numbers since the establishment of a national natural reserve in 2002. (Xinhua/Zhang Meng)

Photo taken with a cellphone through a telescope on Sept. 2, 2014 shows cormorants finding food on the lake of Gahai in Luqu County of Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. The Gahai Wetland, a source area of China's Yellow River, is growing in both water area and waterfowl numbers since the establishment of a national natural reserve in 2002. (Xinhua/Zhang Meng)

Photo taken on Sept. 2, 2014 shows tourists enjoy themselves at a viewing deck on the lake of Gahai in Luqu County of Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. The Gahai Wetland, a source area of China's Yellow River, is growing in both water area and waterfowl numbers since the establishment of a national natural reserve in 2002. (Xinhua/Zhang Meng)

Photo taken on Sept. 2, 2014 shows the scenery of the lake of Gahai in Luqu County of Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. The Gahai Wetland, a source area of China's Yellow River, is growing in both water area and waterfowl numbers since the establishment of a national natural reserve in 2002. (Xinhua/Li Mangmang)

Photo taken on Sept. 2, 2014 shows the reflection of the sky over the surface of the lake of Gahai in Luqu County of Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. The Gahai Wetland, a source area of China's Yellow River, is growing in both water area and waterfowl numbers since the establishment of a national natural reserve in 2002. (Xinhua/Xue Dongmei)

Photo taken on Sept. 2, 2014 shows tourists enjoy themselves at a viewing deck on the lake of Gahai in Luqu County of Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. The Gahai Wetland, a source area of China's Yellow River, is growing in both water area and waterfowl numbers since the establishment of a national natural reserve in 2002. (Xinhua/Zhang Meng)

Photo taken on Sept. 2, 2014 shows water birds finding food at the lake of Gahai in Luqu County of Gannan Tibetan Autonomous Prefecture, northwest China's Gansu Province. The Gahai Wetland, a source area of China's Yellow River, is growing in both water area and waterfowl numbers since the establishment of a national natural reserve in 2002. (Xinhua/Xue Dongmei)