HR: 15:00h
AN: H32E-05    [PDF]
TI: Persistent Spatial Variability of Throughfall Amounts and Intensity Beneath Forest Canopies
AU: * Keim, R F
EM: Richard.Keim@oregonstate.edu
AF: Oregon State University Department of Forest Engineering, 215 Peavy Hall, Corvallis, OR 97331 United States
AU: Skaugset, A E
EM: Arne.Skaugset@oregstate.edu
AF: Oregon State University Department of Forest Engineering, 215 Peavy Hall, Corvallis, OR 97331 United States
AU: Weiler, M
EM: markus@2hydros.de
AF: Oregon State University Department of Forest Engineering, 215 Peavy Hall, Corvallis, OR 97331 United States
AB: Forest canopies are important modifiers of precipitation, both spatially and temporally. Because of the nonlinearities in water fluxes through soils, understanding precipitation redistributions in space and time will allow advances in predicting rainfall-runoff processes in forested watersheds. We found distinct spatial patterns of throughfall persisting in time in three forest stands in the Pacific Northwest, USA. Variograms of storm-total throughfall, collected in small gauges, differed by stand but were consistent among storms within each site. Nondimensionalizing throughfall amounts in the small gauges revealed persisting wet and dry areas, which preserved variograms through time deterministically instead of simply statistically. Cumulative distribution functions of study-total throughfall at each gauge were useful for characterizing persistence of throughfall variability. We measured throughfall intensity within storms using larger throughfall gauges attached to tipping buckets. By comparing these data to rain gauges in nearby openings, we quantified attenuation of rainfall intensity by canopies. There was both temporal and spatial variability in intensity attenuation. Spatial variability was low under a homogeneous canopy of young conifers, but high under a heterogeneous canopy of old-growth conifers. High intensity attenuation was generally correlated with low storm-total throughfall. These persisting patterns in throughfall amounts and intensity suggest there may be corresponding variation in infiltration and soil water movement.
DE: 1854 Precipitation (3354)
DE: 1860 Runoff and streamflow
DE: 1866 Soil moisture
DE: 3322 Land/atmosphere interactions
SC: Hydrology [H]
MN: 2003 Fall Meeting