Runoff generation and separation are key processes for a simulation of hydrological models such as precipitation-runoff model and hydrological forecasting models in both local and regional scales.Nevertheless, determining the ratio of runoff components including base flow,ice-melted water and precipitation are very complicated due to non-availability of hydrological data for ungauged basins.While limited data can be collected in some basins, large errors brought by simply using mean value of each hydrological parameter greatly affects the accuracy of hydrograph separation at watershed-scale.We present a simple method (HySis model) based on inequality systems with hydrological and geochemical data as constraints.HySis model takes account of both mass conversation equations and varying values of each hydrological,geochemical and isotopic parameter, and finally generates not a specific value but an accurate range of recharge ratio of each component.