The Site is a near-natural wetland covering some 72% of the Yeya Lake Nature Reserve. The Site features marshes which are representative wetlands of the biogeographical region but also unique to Beijing. The hydrological processes are mainly influenced by the Guishui River and the Guanting reservoir, which has a storage capacity of about 4 billion cubic metres. 501 plant species, 361 birds, five amphibians, 13 reptiles, 16 mammals and 25 fish are found in the Site. Three of the bird species – the speckled reed warbler (Acrocephalus sorghophilus), Baer’s pochard (Aythya baeri) and yellow-breasted bunting (Emberiza aureola) – are critically endangered, eight are endangered and 14 are vulnerable. In the seven years to 2022, more than 20,000 waterfowls were recorded in the Site, many of them migrating on the East Asian-Australasian Flyway. The Site provides various ecosystem services to over 20 million people in Beijing which includes water conservation and regulation, climate regulation, research, education and tourism.