Examining the results from the Asu catchment in a wider Amazonian context
Martin
George
Hodnett, Free University of Amsterdam, mhodnett@lineone.net
(Presenting)
Javier
Tomasella, CPTEC - INPE, javier@cptec.inpe.br
Waterloo
Maarten, Free University of Amsterdam, watm@geo.vu.nl
Luz
Adriana
Cuartas, CPTEC - INPE, adriana@cptec.inpe.br
Antonio
Donato
Nobre, INPA, anobre@ltid.inpe.br
The important results from the 6.4 km2 Asu catchment are examined in a wider context. These were: the importance of storage in the deep unsaturated zone and groundwater in the water balance (?memory effect?), the scale dependence of the processes of flow generation, and the sandy soils of the valley/floor being the main source of DOC in streamflow. The storage capacity in the Asu catchment, and areas with a similar deep and permeable geological sequence, is large and catchment storage does not return to the same level each year. The assumption that the net annual storage change is zero would cause much noise in model results, and erroneous estimates of evapotranspiration from rainfall and runoff data.
In the headwater areas of Asu (areas of a few ha), throughflow and return flow can cause surface runoff, but scaling up from such small areas would give misleading results. Saturation excess overland flow (SOF) from the saturated valley floor was the main process of runoff generation in Asu. The percentage of total runoff occurring as stormflow depends on the proportion of the catchment area occupied by valley floor. In catchments with a shallow depth of weathering, the proportion of baseflow will be smaller because of the low storage capacity. Storm runoff can be generated as SOF, and from a larger area of the catchment, when a perched water table builds up on the unweathered bedrock. The amount of storm runoff will depend strongly on the rainfall distribution.
Submetido por Martin George Hodnett em 25-MAR-2004
Tema Científico do LBA: SH (Hidrologia e Química das Águas)