Low Flow Scaling with Respect to Drainage Area and Precipitation in Northern Iran

Abstract

Low flow spatial scaling relationships have been defined by log-log linearity between 7-, 15-, 30-, and 60-day low flow probability weighted moments (PWMs) and drainage area size in north of Iran. The PWMs are used to avoid the influence of outliers. Across the entire region, the regression relationship is not significant which is believed to be due to climate heterogeneity of the region. Dividing the region into two humid and semiarid regions, the log-log relationship is found to be significant for the humid subdivision while it is not significant in semiarid region. This implies that in a heterogeneous climate regime, scaling alone is a poor method for extending low flow at-site probabilistic behavior to a region. However, for the semiarid subdivision, the relationship between mean annual rainfall and PWMs verges on significant which suggests to the hydrologist that other alternatives to drainage area size should be examined for scaling low flows in such regions.