Aerial photo taken on July 29, 2019 shows a view of the Gahai Lake of Luqu County in Tibetan Autonomous Prefecture of Gannan, northwest China's Gansu Province. The area of Gahai Lake, known as a large wetland at the Qinghai-Tibet Plateau as well as one of the main headwaters of the Yellow River, has been expanding and reached 2,700 hectares due to plentiful rainfall and improvement of its ecological environment in recent years. (Xinhua/Ma Ning)