Over the past few decades,many numerical streamflow prediction techniques using observed time series(TS)have been developed and widely used in water resources planning and management.Recent advances in quantitative rainfall forecasting by numerical weather prediction(NWP)models have made it possible to produce improved streamflow forecasts using continuous rainfall-runoff(RR)models.Hydrological modeling aims to place the disposal of water actors,very simple tools hydrological simulation to start with,the basic observations made on rainfall until the reproduction of the response the flow of a basin.The aims of this work consist,first,of testing the conceptual model GR4J(Genie Rural a4parameters Joumalier)performances of the rain-flow in mid-subtropical monsoon environment watershed and secondly,of highlighting the contribution of different optimization techniques(Willmot,RMSE,MAE,and Nash)in determining the optimal parameters of the model.In terms of the model performances,we obtained satisfying results(Nash=72％).Thirdly we have forecasted our rainfall data using SARIMA;rainfall forecasting could play a significant role in the planning and management of water resource systems also.In this thesis,univariate Seasonal Autoregressive Integrated Moving Average(SARIMA)models were used to forecast daily rainfall for365days lead-time for12rainfall stations of Lijiang.The best SARIMA models were chosen based on the AIC,BIC,MSE,RMSE,MAPE,and MAE.A validation check for each station was performed on residual series.Residuals were found white noise at almost all stations except three stations.Besides,lackof fit test and MAE confirms all the models were fitted satisfactorily.The predicted results from the selected models were compared with the observed data to determine prediction precision.We found that selected models predicted daily rainfall with a reasonable accuracy.Therefore,year-long rainfall can be forecasted using these models.Finally,the forecasted rainfall results were used again as inputs in our GR4J model in order to calculate the forecasted flow;these results confirm the capability of the conceptual models in the operation of simulation even if they were validated by a modest rate of the Nash index.