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Abstract:
The time of peak discharges in rivers is considered good indicator in the climatological variation in the rivers basins reflecting their values for long periods. The water quantities of the melted snow during spring season is one of the main sources feeding rivers in the world like Tigris river and its tributaries in Iraq. The climate variation on the rivers basin lead to variation in their hydrograph shape specially in the peak discharge values and its arrival time. The daily recorded discharges data for three tributaries of Tigris river (Greater Zab, Lesser Zab and Khazir) for fifty years (1965-2014) were analyzed after the division into two periods (1965-1989) and (1990-2014). One of previous statistical indices was applied in analyzing the time of peak discharges measured at each river like the annual center time of the discharges (CT). This is the time at which half of annual volume of flowing discharges is passed. The recorded air temperature criteria in the climatological stations is depended in this analysis too. An early arrival time of peak discharge as a result of an advancement in the melting snow was observed to be (6.2, 7.1,10.4) days for the Greater Zab, Lesser Zab and Khazir rivers meteorological stations respectively. This is due to 3.3°C increasing in the average maximum recorded air temperature in the climate stations during the previous forty years.
