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Electronic journal of the International Association
for Environmental Hydrology
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JEH Volume 7 (1999), Paper 18, November 1999 Posted
November 24, 1999
EFFECTS OF RAINFALL VARIABILITY ON SPATIAL ACCUMULATION OF PEAK RUNOFF
AND EXCESS RUNOFF DEPTH: LITTLE WASHITA RIVER BASIN, OKLAHOMA, USA
A. Komuscu
State Meteorological Service, Research Department, Kalaba, Ankara,
Turkey
D. Legates
Southern Regional Climate Center, Louisiana State University, U.S.A.
ABSTRACT
This paper demonstrates the spatial variability of surface runoff components,
accumulated peak flow (Q a ) and excess runoff depth (R a ), in response
to varying distribution of precipitation on a basin scale. A hydrologic
representation of the Little Washita Basin was developed using HEC-1, a
lumped parameter-based single event model. Accumulation of peak flow and
excess runoff was computed at 20 locations along the drainage network.
The analysis focused on the differences in the spatial and temporal distribution
of precipitation while total basin rainfall and basin hydrologic conditions
are held constant. The study also relates variability in the surface flow
to the storm’s duration and depth. The analysis shows that heterogeneous
rainfall intensities in both space and time greatly influence peak flow.
Uneven spatial distribution of precipitation directly contributes to higher
peak flows, particularly in storms of short duration. The larger variabilities
with Q a are observed when rainfall has a nonuniform distribution and high
intensities. When the distribution of rainfall was more even, the resulting
Q a and R a showed less variability. The contribution from new subwatersheds
to Q a in a downstream direction is usually less if the high intensity
rainfall areas are located far from the centroid of the basin. Coupled
with the steady increase in drainage area in the downstream direction,
changes in the magnitude and variability of Q a decrease. Proximity of
high intensity rain cells to basin outlet also gains major importance in
the spatial behavior of R a . The study also shows that for high storm
totals, flow volumes and peak flow can be simulated more accurately compared
to low storm totals.
Reference: Komuscu, A. U. and D. R. Legates; Effects of Rainfall
Variability on Spatial Accumulation of Peak Runoff and Excess Runoff Depth:
Little Washita River Basin , Oklahoma, USA, Journal of Environmental
Hydrology, Vol. 7, Paper 18, November 1999.
Dr. Ali Umaran Komuscu
State Meterological Service
Research Department
Kalaba, Ankara
06120 Turkey
E-mail: aukomuscu@meteor.gov.tr