Estimation of runoff hydrograph from ungauged catchments has been an important subject of research for
planning, development and operation of different water resources projects. In this study, Nash's linear
reservoir model was applied to predict direct runoff hydrograph characteristics in Jafar-Abad watershed
(109 km2) located in Golestan province. Using hourly hydro-meteorological data, the Nash model parameters
(n and k) calculated by Moment method for 33 storm events. Then the mean value of n and k, were
used for simulation of second subset of storm events as model validation. The efficiency of Nash model
was evaluated by statistical comparison with the observed hydrographs. The results indicated that the
model predicts direct runoff hydrographs with good accuracy, 70 % according to the Nash-Sutcliffe criterion.
Also mean relative error of peak discharge, relative error of time to peak, model bias for water balance
and RMSE are 10 %, 10 %, 25% and 3.94, respectively. The good agreement between observed and
simulated hydrographs shows that n and k were calculated reasonably by Moment method. Results show
that the Moment method in estimation of n and k parameters gives good results. So that regionalization of
Nash's model parameters (n and k), in ungauged catchments is suggested for development and application
of this hydrological model.