LINKING PARAMETERS ACROSS SCALES - SUBGRID PARAMETERIZATIONS AND SCALE-DEPENDENT HYDROLOGICAL MODELS

It is argued that the aggregation approach towards macroscale hydrolog ical modelling, in which it is assumed that a model applicable at smal l scales can be applied at larger scales using 'effective' parameter v alues, is an inadequate approach to the scale problem. It is also unli kely that any general scaling theory can be developed due to the depen dence of hydrological systems on historical and geological perturbatio ns. Thus a disaggregation approach to developing scale-dependent model s is advocated in which a representation of the distribution of hydrol ogical responses is used to reflect hydrological heterogeneity. An app ropriate form of distribution may vary with both scale and environment . Such an approach is dependent on the data available to define and ca librate the chosen subgrid parameterization. A parameterization based on a minimum patch representation is suggested and the problems of ide ntification at the larger scale discussed.