Comparison of Separation Methods for Baseflow from Direct Runoff in Doroud Basin, Lorestan, Iran

Abstract

As groundwaters make an important part of the permanent rivers flow, their role in maintaining the life of rivers and creating ecological balance in watershed can be determined by knowing the base flow contribution. Moreover, identification of runoff production processes is crucial for assessing the effects of climate change and landuse on the hydrologic response of the watershed. In the current study, the base water separation in Doroud watershed located in Lorestan province with 6 study areas was performed during a period from 1982 to 2011 using PART, one parameter recursive digital filter (Lyne -Hollick) and two parameters recursive digital filter (Eckhart) with filters value of 0.925, 0.95, 0.975, and 0.99. Then the results obtained by these methods were compared with those of BFI method. The comparisonshowed that Lyne -Hollick method with filter value of 0.975 was the best method to separate base water from direct runoff in Doroud watershed. In Bayatan watershed, Silakhor sub-watershed, Ab Sardeh sub-watershed, Sarab Sefid sub-watershed, and Gale Rood sub-watershed, the Eckhart's method with filter value of 0.975, Lyne -Hollick method with filter value of 0.975, PART and Lyne -Hollick method with filter value of 0.975, Lyne -Hollick method with filter value of 0.95, and Lyne -Hollick method with filter value of 0.925 were the suitable methods for hydrograph decomposition, respectively. Considering the results obtained by this study and having statistics of this watershed flow rate ona daily basis, the abovementioned methods can be used in future years for hydrograph decomposition.

Keywords

• baseflow index
• hydrogragh
• lorestan province
• recursive digital filter