The Precordillera area of the Andes Mountains (Mendoza, Argentina) is affec
ted by severe flash floods, caused by heavy rainfall events of short durati
on and high intensities. A, telemetric network, installed on a pilot zone s
ince 1983, provided a set of about 150 rainfall events. In addition, about
50 hood events were recorded at the outlet of a 5.47 km(2) catchment. The d
istributed model Areal Non-point Source Watershed Environment Response Simu
lation was adapted to this catchment and applied continuously over the peri
od 1983-1994. The year 1985 was used for calibration. The model was able to
reproduce runoff volume with an efficiency of 0.6, and peak discharge with
an efficiency of 0.46. The largest events were however underestimated, alt
hough the model was able to reproduce the sharp increases in streamflow reg
istered by the sensor. Based on the assumption that the model had captured
the catchment behaviour, it was used to determine the main processes involv
ed in runoff generation. The combination of rainfall and soil variability,
mainly associated with a quasi-impervious area in the middle of the catchme
nt, was found to explain the rapid increases in streamflow. Vegetation, sur
face storage capacity, and initial soil moisture were also influential but
with a much smaller magnitude than the combination of rainfall and soil var
iability. (C) 1999 Elsevier Science B.V. All rights reserved.