Students at a primary school in Liaocheng, East China's Shandong province, take part in an experiment aimed at detecting polluted water, on March 22, as part of activities marking International World Water Day, which is held annually. The United Nations General Assembly designated March 22, 1993, as the first World Water Day, and it says it aims to focus attention "on the importance of freshwater and advocating for the sustainable management of freshwater resources". [Photo by Zhang Zhenxiang/Asianewsphoto]