Analysis of Monthly Flow Discharge Occurrence Pattern using Power Laws Analysis in Some Hydrometric Stations of Mazandaran Province

The assessment of hydrologic wet and dry periods is the primary and necessary basis of water resource management and planning which need to study and understand of drought occurrence. The aim of this study is the use of Power Law Analysis and analyzing wet and dry period’s patterns of river flow in some gauge stations of Mazandaran Province. Toward this attempt, wet and dry periods of monthly discharge time series in 26 hydrometric stations have been analyzed through a 36-years study period. Therefore, average monthly discharge, threshold limit and start and end of wet and dry spells were calculated and then the number of wet and dry spells occurrence sequences from 1 to 41 months were determined. Results showed that there is an straight relationship between the severity and duration of dry and wet spells. The minimum severity of dry and wet spells were observed in Polur and Hanisk stations with the line slope of -0.87 and -1.29 in southwest and western parts of the Mazandaran Province. The maximum flow duration for dry and wet periods (122.09 and 145.89) were identified in Qoran Talar station at the center of study area. In other words, stations in the main branches of southeast and center of Mazandaran province have dry and wet flow durations more than other studied stations. The proximity of scatter plots to the straight line or parallel lines without intersection in the study area represented a homogeneous regime of dry and wet periods and significant changes with the time hadn’t observed. In this regard, it can be noted that the periodic pattern of monthly discharge and its duration can be determined using Power Law Analysis method.