Spatial and Temporal Variability of River Flow in Mazandaran Province

Variability is natural in rivers flow. Rivers flow has large variability in time and space scales. The most part of this variability is due to climatic factors. The main objective of this study is the annual variability of monthly maximum discharge in Mazandaran province. For this purpose, data from 19 stations, which has collected for at least 30 years (87 to 1386 since its establishment in blue), are used.  Initial investigation shows that, relative to the maximum monthly discharge occur in spring and fall in the rivers. For detail study harmonic analysis was used. This method showed the highest percentage of variance explained by the first harmonic of 60% was observed in Kasilian station. Annual variability of maximum monthly flow in this station was during the considered period of is generally annually. In Most rivers in the second harmonic has a very large role in explaining the variance of the data. Safarud station PVR2 is more than 68%. Thus the dominant pattern of monthly maximum fluctuations in this area has six-month period. The first harmonic of the peak time (T1), generally occurs in April and the second harmonic peak (T2) between March and April with a six-month alternation between September and October. The peak time of the harmonics, which models the maximum monthly flow is influenced by two fundamental factors. During spring (March-April) due to the occurrence of maximum monthly flow is the melting snow and the second peak occurred in autumn (October-November) is affected by the rainfall regime that is generally fall