This research is to evaluation and analyzing the main aspects of spillway design
for Chaq-Chaq dam in north of Iraq in Suleimaniya governorate, with help of the
hydraulic, hydrologic and climate data collecting. Four different distribution models
are used in order to conduct the analysis required to find the different return periods
of flood, based on the expected daily rainfall depth, also the result was compared
with the study of Sogreah consulting company .Analysis of data shows that the
length of the spillway of Chaq-Chaq dam should be increased by about 206% to
accommodate the maximum flood discharge according to Extreme Value type I
distribution with return period of 1000 year.