Study of efficiency of various base flow separation methods in arid and semi-arid rivers (Case study: Hablehroud basin)

Base flow is an important part of river flow, which shows stream response to precipitation. Separation of base flow through hydrograph analysis provides useful information about characteristics of water storage, which drains into rivers. Base flow is usually related to the evacuated water from underground water reserve. It is useful to understand base flow in order to measure water quality and conditions of low flow that can be utilized for calibrating and validating of hydrologic models. There are several methods for hydrograph separation. In this research, Recursive Digital Filters of one and two parameters, PART and Local Minimum methods were used in order to separate hydrograph of flow into two parts (direct runoff and base flow) in four hydrometric gauging stations, located in Hablehroud basin. Results indicated that Local Minimum method show the best estimation of base flow index in all stations, except of Namrood. Meanwhile, in Namrood station, Recursive Digital Filters method with α value of 0.975 provided the most accurate estimations.