Baseflow estimation of the source regions of the Yellow River

Baseflow plays an important role in water security,food security,water resource assessment and investigation,and water allocation.Baseflow is mainly the recharges from groundwater.The characteristics of recharge and discharge of groundwater are very important to efficient groundwater management and sustainable development,and are vital to the control of pollution.Runoff of the source regions of the Yellow River accounts for more than 35% of the total ruhoff of the Yellow River basin.Baseflow is a very important water supply source in the low flow season and also an important supply cource in the headwaters,hence,it's essential to estimate baseflow in this area.There are numerous baseflow separation methods such as analytic methods and graphic methods,but they have their own shortcomings and can't be applied extensively.In this study,two physically based and two parameters based baseflow separation methods-Kalinin method and digital filiter method-were selected.First the Kalinin baseflow separation method was improved based on the climate condition of the study area and a new procedure was developed and then the sensitivity analysis was conducted for the two methods.The results show that the baseflow separated by digital filter baseflow separation method is very sensitive to the parameter's variation,and the filter parameter β is the control factors of the baseflow.With the increase of β the separated baseflow decreases and vice versa.The sensitivity(analysis) curves are very alike as to the runoff of different years.The baseflow separated by the modified Kalinin method is strongly affected by the runoff hydrograph,generally,the baseflow increases with the increase of recession coefficient and is not sensitive to the variation of parameters.