Principle of hydrograph separation based on isotope and hydrochemical methods was introduced.It provided an overview on the development and advantages and disadvantages of all kinds of hydrograph separation models.Runoff(new water) and groundwater(old water) were separated in the initial two-component model,without considering soil water.There are runoff,groundwater,soil water in the three-component model which has a wide application;multi-component model is suited to basins that have complex water sources....