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To estimate cheaply the infiltration/runoff of typically unsteady rainfall events for purposes of watershed modeling, a method known as 'time compression' has been tested against hysteretic Darcy computations. This method assumes that for a given soil the maximum infiltration rate is simply a function of the cumulative infiltration, regardless of the rainfall versus time history. Hysteretic characteristics from soils measured by Topp (1971) were employed in the Darcian calculations. The appraisal proved generally encouraging for application of this approximation to watershed modeling. The maximum infiltration rate was uniformly underestimated to a moderate degree in the early minutes of a downpour commencing late in an unsteady event.As a part of the International Biological Program the authors have been trying to incorporate the extensive wor k of soil physicists more effectively into the analysis of watershed hydrology. The philosophy has been to cut corners freely to make reasonable approximations wherever necessary order to achieve quantitative field modeling experience more quickly. By generating specific models from soil physics concepts and exposin• these models to the test of practice one can hope to harness the eoncepts to practical uses while bringing to light those areas of deficiency most urgently in need of research.Although the objective has been to apply existing methods rather than to develop new ones, the very first step of the hydrologic cycle, the partitioning of rainfall events into surface runoff and soil infiltration, was not found in a practical state of

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