Geographical Research

Hydrograph analysis is a complex problem in a variety of water resources investigations and its estimate is critical in the assessment of low flow characteristics of river for use in water supply، water management and pollution assessment. The paper describes different methods of base flow separation based recession analysis from daily river flow records and distinguishes the most suitable method in some hydrometric stations of Azarbaijan province. An automated base flow separation with different parameters –with different parameters of 0.9 to 0.975- and local minimum techniques has been tested against correlation method of master recession curve with base flow index. unnecessary of calibration in this algorithms is made easy to use them and Finally، use of digital filter with the parameter set to 0.925 was found to be a most accurate method of base flow separation in study region. Also، Recession constants have fluctuations between 0.65 to 0.83 which reveal role of ground water and base flow in river recharging. Continuous investigations of daily flow data in long term duration is another benefit of this algorithm that can be used for leaching control and pollutions entry into soil in environmental plannings.