Iraq relies greatly  on  the  flow of  the  Euphrates  and  Tigris Rivers  and  their tributaries. Five tributaries namely Khabour, Greater Zab, Lesser Zab, AlAd- hiam  and  Daylia,  which  are  the  major  tributaries  of  Tigris  River,  sustain Northern  Iraq  Region,  a  semi-arid,  mainly  a  pastureland.  These  tributaries contribute about 24 km3  of water annually. The discharge in the tributaries, in recent  times,  has  been  suffering  increasing  variability  contributing  to  more severe droughts and floods apparently due to climate change. This is because there were no dams constructed outside Iraq previously. For an appropriate appreciation,  Soil  Water  Assessment Tool  (SWAT)  model  was used  to evaluate  the  impact  of  climate  change  on  their  discharge  for  a  half-centennial lead time to 2046-2064 and a centennial lead time to 2080-2100. The suitability of the model was first evaluated, and then, outputs from six GCMs were incorporated  to  evaluate  the  impacts  of  climate  change  on  water  resources under three emission scenarios: A1B, A2 and B1. The results showed that wa-ter resources are expected to decrease with time.