GEOG 431
Geography of Water Resources


image of Comte Georges-Louis Leclerc de Buffon
In general, the more one augments the number of divisions of the productions of nature, the more one approaches the truth, since in nature only individuals exist, while genera, orders, and classes only exist in our imagination.

Comte Georges-Louis Leclerc de Buffon (1707-1788)
French naturalist, author, artist Histoire Naturelle (1749),
trans. by John Lyon, The 'Initial Discourse' to Buffon's
Histoire Naturelle: The First Complete English Translation,
Journal of the History of Biology, 9(1), 1976, 164.

No classification system can capture effectively all of the inherent variability in natural systems, nor can it provide a foolproof determination given the different experiences of users. Most classification systems used internationally or regionally are designed to distinguish among major types aquatic ecosystems with recognizable differences. Some are directed at a specific type, such as wetlands or streams, but many are designed to address all fresh and marine waters for the geographic area of interest. The following classification systems, although focused on wetlands, address a broader set of aquatic ecosystems (Cowardin et al. 1979, Brinson 1993, Warner and Rubec 1997, Ramsar 2009, 2013, Brooks et al. 2011). Whatever the intent and potential use of the classification system, it is critical that users consider the landscape and hydrologic contexts of each type. How large an area is being classified? A river channel and the associated floodplain on both sides of the channel, or just the wetland associated within a property on the upland edge of a floodplain? Context really matters, and should be carefully and succinctly documented.

When seeking to classify a body of water, the most fundamental question the user must ask is, How was it formed? which can be stated as, What is the origin of this body of water? If this question is thoughtfully answered and described in a brief narrative, then the actual label assigned to the type matters less, because the user will have considered where and how the water fits in a given landscape and hydrologic setting. Obviously, this is more relevant for regions where aquatic ecosystems do not form the dominant matrix of a landscape (e.g., coastal salt marshes, bottomland hardwood forests). For example, is it a depression that is isolated during drier times of the year, but located in a floodplain setting? Or is it isolated from all riverine influences, receiving only a combination of groundwater and precipitation? Clearly, these types of wetland depressions are distinctively different in many of their attributes and functions, but they could have the same morphometric dimensions.

Many waters have characteristics of multiple types, warranting a dual label (e.g., depression/slope) just as National Wetland Inventory (NWI) mapping for the U.S. recognizes mixed vegetation classes (e.g., forested/scrub-shrub, FO/SS). Thus, it is important to recognize these distinctive elements and document the reasons for labeling the water as a specific type. This is especially important when addressing types that occur along a broad hydrologic gradient and when a group of microhabitats occur in a cluster. Thoughtful selection of classes supported by careful documentation will make any classification system more consistent among users (Brooks et al. 2011).