Fl. Ogden et Py. Julien, RUNOFF SENSITIVITY TO TEMPORAL AND SPATIAL RAINFALL VARIABILITY AT RUNOFF PLANE AND SMALL BASIN SCALES, Water resources research, 29(8), 1993, pp. 2589-2597
Surface runoff sensitivity to spatial and temporal variability of rain
fall is examined using physically based numerical runoff models. Rainf
all duration t(r) and temporal sampling interval deltat are varied sys
tematically, and normalized by the time to equilibrium t(e). The relat
ive sensitivity R(s) is defined as the total volume of outflow variabi
lity over 50 Monte Carlo simulations normalized by the rainfall volume
and the coefficient of variation of rainfall. Relative sensitivity to
temporal rainfall variability increases with both t(r) and deltat. An
asymptotic R(s) value proportional to (deltat/t(e))1/2 is approached
as t(r) >> t(e). Two-dimensional surface runoff simulations with spati
ally variable rainfall, without temporal variability, on two watershed
s indicate that R(s) decreases as t(r)/t(e) increases. Normalized R(s)
versus t(r)/t(e) curves are identical for two watersheds and a one-di
mensional overland flow plane. These findings indicate that spatial va
riability is dominant when t(r) < t(e), while temporal variability dom
inates when t(r) > t(e), particularly for larger values of deltat/t(e)
.