Abstract
The timing criterions represented by the time center of mass flow (CT), spring pulse onset (S.P.O) and time of flood peak discharge (TP) of rivers are considered good indicators for the climate change occurs on their watershed areas. Spring snowmelt is a main water resources for large number of rivers in the world such as lesser Zab river in Iraq. An analysis for the daily discharge of lesser Zab measured at Dokan station and for climatic data such as temperature and rainfall measured at Alsulaymania meteorological station is carried out for spring and winter seasons of the 50 water years (1960-2009) after dividing this study period into two equal consecutive eons.The results indicate an early advance for the average values of these above criterions in the second eon by 5 , 5 and 15 days respectively in-comparison with the first eon as a result of early snowmelt feeding the river due to increasing temperature in the second eon (1.33)°c and decreasing rainfall (16) mm. The earlyadvance in the timing criterions of the flow hydrograph occur from snowmelt may effect on the storage efficiency and operation of reservoirslocated on the river and require taking these hydrological changes intoconsiderationinthewaterresourcesprojects.
