Spatial and temporal predictions of soil moisture patterns and evaporativelosses using TOPMODEL and the GAS-FLUX model for an Alaskan catchment

By using topographic indices as derived from a Digital Terrain Models (DTM) , it is possible to represent the heterogeneity within a landscape. This he terogeneity can reflect both long term evolutionary patterns seen in a land scape and the short term forcing of flow dynamics during storm events. By s patial analysis, the linkage between the geomorphological-hydrological-plan t physiological phenomena can be examined. In this study, a direct link wil l be established between the topographically-driven hydrological phenomena and the eco-physiological response. The topographic distribution function o f TOPMODEL is used to control the spatial and temporal flux of the channel flow and water table. The plant physiological model GAS-FLUX is used to giv e a spatially and temporally dissaggregated species-sensitive estimate of e vapotranspiration flux. Evapotranspiration is sensitive to the vegetation p henology, to tundra community physiology and to the temperature regime. A s imple linking of TOPMODEL and the GAS-FLUX model is applied to a summer sno w-free period to the Imnavait catchment, Alaska (2.2 Km(2)). A species-sens itive evapotranspiration model proved to give the highest quality results w hen validated against flow observations. Predicted dynamics of variable sou rce area and the component hydrological processes are illustrated.