The present invention relates to a method of forecasting reservoir inflow for hydropower reservoir operation. The method comprising the steps of collecting reservoir inflow data as an input; employing a neural network and provide an analysis on the input; and determining new reservoir inflow data based on the analysis. The present invention also relates to a system of forecasting reservoir inflow of hydropower reservoir operation comprising means for collecting reservoir inflow data as an input; means for accessing a database having stored therein historical reservoir inflow data; means for analyzing the input and compare with the database; and a front end system to receive a request from a user.