Abstract. In a study of the spatial variability of rainfall across a network of 46 raingauges in a 4 km² rainforest catchment in the interior of northeastern Borneo, seasonal rainfall totals were correlated with raingauge separation distance, aspect and relief. A very high degree of spatial variability in seasonal totals across a very small area was found, even in comparison with other regions experiencing convective rainfall. Moreover, it shows systematic, stochastic structure in rainfall is present over scales of 10s to 100s metres; these patterns change from the southwest monsoon (May-October) to the northeast monsoon (November-April). Local associations with aspect and relief are present but the seasonal changes in rainfall pattern over the whole 4 km² catchment must relate to more complex local topographic effects on the regional windfield.

Keywords: catchment, Malaysia,monsoon, rainfall, spatial variability