Topography and hydrology
Ba Be National Park is centred on Ba Be lake. The name Ba Be means "three lakes", although the lake is one continuous water body, 8 km long and up to 800 m wide. At an altitude of 178 m, Ba Be is the only significant natural mountain lake in Vietnam. It is up to 29 m deep, and contains numerous small limestone islets.
The site ranges in altitude from 150 to 1,098 m. The geology of the area is predominantly limestone, with numerous rugged peaks and deep, steep-sided river valleys. The limestone karst landscape contains many caves, the largest being the 300 metre-long Phuong cave, through which the Nang river passes.
Ba Be lake is fed by the Ta Han, Nam Cuong and Cho Leng rivers, which form the above-ground hydrological system in the southern part of the national park. The lake drains into the Nang river, which flows through the north of the park. The Nang river then flows southwards, eventually meeting the Lo river in southern Tuyen Quang province, before joining the Red River west of Hanoi.
The forest at Ba Be can be classified into two main types: limestone forest and lowland evergreen forest. The limestone forest is distributed on steep limestone slopes with shallow soil, and covers a large proportion of the national park. This forest type is dominated by Burretiodendron hsienmu and Streblus tonkinensis. Lowland evergreen forest is distributed on shallow slopes with deeper soils. This forest type has a higher tree species diversity than limestone forest and has a richer ground flora.
With regard to mammals, the site is of particular interest for the presence of the globally vulnerable Owston's Civet Hemigalus owstoni and Francois's Leaf Monkey Trachypithecus francoisi, although it appears that only one group of 7 to 13 Francois's Leaf Monkeys remains.
It is highly unlikely, however, that the globally critically endangered Tonkin Snub-nosed Monkey Rhinopithecus avunculus continues to occur within the core zone of Ba Be National Park. Information from Ba Be National Park staff suggests that the species may have occurred in the north-west of the national park as recently as 1997.
However, surveys by BirdLife International and Fauna & Flora International on behalf of the Creating Protected Areas for Resource Conservation Using Landscape Ecology (PARC) Project, in 2002 and 2003, provided no evidence in support of the supposition that the species remains at Ba Be.
Ba Be is unique amongst Vietnamese protected areas for the diversity of freshwater habitats. This is reflected to some extent in the diversity of fish species found at the site. Although recent surveys by the PARC Project have documented the existence of several endemic fish species, more work needs to be conducted in this area.
Ba Be also supports a high butterfly species richness. During surveys in 1997 and 1998, a total of 332 species were recorded at the national park, of which 22 were new records for Vietnam.
Ba Be lake is a popular tourist destination. A total of 8,733 visitors stayed at national park accommodation in 2003, 10% of whom were international visitors. Together with the river network, the lake is also an important means of communication for local communities, and the road heads on its eastern and western shores are linked by ferry. However, the construction of the new road around the lake has minimised the need for a ferry. The lake is also an important source of fish for local communities, and plays an important role in the regulation of flooding of the Nang river. Ba Be lake, therefore, has numerous economic and environmental functions, both locally and on a wider scale.