What is the average annual rainfall and evaporation in Changsha?

Can you tell me the average rainfall and evaporation in Changsha over the years? I want to inspect a small hydropower project, and I need to know the annual average water quantity in the reservoir catchment. It is best to have statistical data for 30 to 50 years. I estimate that the average annual rainfall is about 1500mm, and the average annual evaporation is about 500mm. I don't know how much it will deviate from the actual hydrological data.