An analysis was performed on the treated water from two water treatment plants in Baghdad
city. This analysis was used to evaluate the stability of the treated water from these plants and
that will flow in the distribution system to consider its corrosivity. The variation in water
stability with time and distance from the north to the south of Baghdad was indicated. The
analysis showed that the flowing water in the distribution system in Baghdad is corrosive to very
corrosive water by calculating Ryznar stability index (RI). In Al- Karkh WTP in the north, RI
maximum ranged between 7.958 to 9.403 where RI minimum ranged between 7.03 to 7.915.
Where in the south Al-Rasheed WTP, RI maximum ranged between 7.119 to 8.63 and RI
minimum ranged 6.679 to 7.994. The corrositivity of water decreased in the water flowing down
stream. The water quality parameters affecting RI was discussed which were calcium, alkalinity,
total dissolved solids and pH.