This study is an assessment of the importance of precipitation accuracy on the rainfall‐runoff modeling of a small catchment. Two mathematical models were used in the investigation: a deterministic rainfall‐runoff model based on the kinematic wave approximation and a nonstationary time‐varying multidimensional rainfall generation model. It is implicitly assumed that this rainfall generation model is an appropriate mathematical representation of the natural phenomenon of rainfall. The deterministic rainfall‐runoff model is used to represent the 26.5‐mi2 catchment of the Rio Fajardo in northeastern Puerto Rico. The rainfall model generates synthetic rainfall which serves as the input to this runoff model. The influence of the spatial distribution of the rainfall input on the discharge is analyzed by using 1 rain gage or 20 rain gages to record the synthetic storms. The isohyetal maps and hyetographs of the synthetic storms, together with the storm hydrographs produced by the runoff model, are analyzed, with specific attention given to the volume of storm runoff, time‐to‐peak runoff, and peak runoff. The experiments show that the spatial distribution of rain and the accuracy of the precipitation input have a marked influence on the outflow hydrograph from a small catchment. Copyright 1979 by the American Geophysical Union.
