INTRODUCTION
As the important factors of runoff in hydrological cycle,
its change process is bound to affect the comprehensive
development and utilization of water resources, scientific
and effective management and reasonable optimal
management[1].Separating the runoff process and water
source partition is an important problem in engineering
hydrology ,it is widely used in rainfall-runoff simulation,
river basin water resources assessment and
investigation[2].Based on the data of inflow runoff into
Qingshitan reservoir during 1958-1990 years in this
paper[3-4],the digital filter technique is used to separate the
data of inflow runoff into surface runoff and baseflow .
The characteristic value and change trend of surface
runoff and baseflow are analyzed; it expects to provide
certain basis for reservoir regulation and water resources
reasonable organization.