The development of useful rainfall-runoff relations for small basins is an extremely useful extension of this valuable hydrologic tool. The authors are to be congratulated upon a n excellent paper on an interesting subject presented in a clear and concise manner.
Explanation: The writer is particularly interested in the subject because of his own efforts to develop some methods of computing approximate rainfall-runoff relations in various areas of the world, given a minimum amount of climatological facts and runoff data. I n the course of the writer's investigations, he came to several conclusions which seem to be at variance, to some degree, with the authors'. Firstly, the authors state that experience has shown that the seasonal factor in the rainfall-runoff relation shows little change with in a physiographicaUy homogeneous region. The writer believes that authors may have meant to include similar climate as well as similar physiography. By definition, seasonal curves properly established should largely reflect the influence of the annual climatic cycle on runoff. In many areas of similar physiography, considerable differences have been known to exist in the evapotranspiration losses reflecting the effect of climatic differences. In place of accepting the seasonal curve from an area of one climate and using it foe an area of another climate, the writer has obtained some workable runoff relations by adjusting the seasonal curves for variations in seasonal factors. The factors used included the mean air temperature in January and July, plus the length of the growing season and other climatic data. It seems to the writer, that if acceptable results were obtained by the authors in Georgia, using the seasonal curves of a rainfall-runoff relation developed in Maryland, the effect of differences in climate may have been only partially compensated in the hourly rainfall-hourly runoff portion of the runoff relation. If this were the case, the procedure illustrated in the paper will have limited application.
