Wetland types can be related to the relative importance of the climatological, surface-water and groundwater variables found in the wetland water balance equation. Using this assumption a 12 -fold hydrological classification that includes ombrotrophic, rheotrophic, minerotrophic and omnitrophic wetland types is proposed. Each wetland class can also be assigned a hydrological vulnerability to a number of man's activities and various types of water pollution.
Using Scottish Natural Heritage data, compiled in relation to designation of Scottish Sites of Special Scientific Interest with a wetland component, the classification was tested to assess its usefulness as a first stage in wetland hydrological vulnerability assessment. Despite limited site-specific data, each of 399 wetlands were fairly confidently assigned to one of the 12 classes and thus a provisional assessment of its hydrological vulnerability could be made. It is believed that this classification may have universal application as a first stage in the generalized approach to wetland hydrological vulnerability assessment recently proposed by Lloyd et al. (1993; Journal of Environmental Management 37, 87-102), particularly if it can be linked to a simple lumped hydrological model to test the sensitivity of individual wetlands within any given class.