USING TOPMODEL TOWARDS IDENTIFYING AND MODELING THE HYDROLOGICAL PATTERNS WITHIN A HEADWATER, HUMID, TROPICAL CATCHMENT

Increasing pressure on the tropical environment requires a more thorou gh understanding of hydrological processes as part of reconciling the conflicting demands of economic development vis-a-vis sustainable land management. Using TOPMODEL, a physically based semi-distributed topoh ydrological model, we test its validity in modelling the stream flow d ynamics (hydrograph) in a 1 ha tropical rainforest catchment in French Guiana. Another objective is through field validation of TOPMODEL to ascertain possible runoff generation mechanisms. The field validation of the temporal and spatial hydrodynamics across a rainfall-runoff eve nt reveals that TOPMODEL may be suited for applications to this partic ular tropical rainforest environment; in fact, this is possibly the fi rst successful application of such a model within the humid tropics. T he main reasons why the model was successful are the presumed low hydr aulic conductivities of the subsoil, coupled with the absence of an ad ditional deep groundwater body, the contribution from which has caused difficulties in application of topographically, 'physically' based ru noff models elsewhere in the humid tropics. (C) 1997 by John Wiley & S ons, Ltd.