A Model to Predict Mean Annual Watershed Discharge

A method was developed for the estimation of long term discharge characteristics of small watersheds. It was shown that, besides the annual precipitation and the annual mean temperature, other factors also influence the discharge. Two newly established watershed parameters were developed for improving the long term discharge prediction techniques. The first watershed parameter may be determined from a few years long discharge—precipitation—temperature record. It was shown that the second watershed parameter is related to the drainage density which reflects the soil texture. This study proves the expectation that the long term discharge is higher from watersheds having high drainage densities than the reverse, provided the other factors are identical. The consistent evaluation of the drainage density from aerial photographs requires the application of a system of conventions. The conventions were discussed in detail in the text.