Soil classification systems are analysed to explore the potential ofdeveloping classification systems for catchments. Soil classifications areuseful to create systematic order in the overwhelming quantity of differentsoils in the world and to extrapolate data available for a given soil typeto soils elsewhere with identical classifications. This principle alsoapplies to catchments. However, to be useful, soil classifications have tobe based on permanent characteristics as formed by the soil forming factorsover often very long periods of time. When defining permanent catchmentcharacteristics, discharge data would therefore appear to be less suitable.But permanent soil characteristics do not necessarily match withcharacteristics and parameters needed for functional soil characterizationfocusing, for example, on catchment hydrology. Hydropedology has madecontributions towards the required functional characterization of soils asis illustrated for three recent hydrological catchment studies. However,much still needs to be learned about the physical behaviour of anisotropic,heterogeneous soils with varying soil structures during the year and aboutspatial and temporal variability. The suggestion is made therefore to firstfocus on improving simulation of catchment hydrology, possibly incorporatinghydropedological expertise, before embarking on a catchment classificationeffort which involves major input of time and involves the risk ofdistraction. In doing so, we suggest to also define other characteristicsfor catchment performance than the traditionally measured discharge rates.Such characteristics may well be derived from societal issues being studied,as is illustrated for the Green Water Credits program.
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