Surface water flow samples were collected with distances downstream over Saqlawiya main drain whose stretch of about 24.5 km. The drain travels through different land use pattern, before, flowing into Tigris River. Eight sampling points were carefully
selected downstream the channel during dry season. The examined water parameters were pH, NH3, NO3, PO= 4, BOD5, COD, TDS, S.S, Cl-, SO= 4, Na+ , Ca+2, Mg+2, and Oil and Grease. Descriptive and inferential methods through finding the best curve fit correlation were employed in the study to test the strength of the association between water chemical characteristics and distance downstream the channel. A comparison of the values of chemical parameters at the Al-Saqlawiya Drain-Tigris River meeting shows that nine parameters (i.e. pH, NH3, NO3, PO= 4, BOD5, COD, TDS, S.S, and Oil and Grease) out of the 14 parameters under study decreased in
their concentration at meeting point. In a further analysis, predictive models were obtained through using six sampling points (0. 1, 3, 5,7, 8) and leaving three (2, 4, 6) as activation function. The percentage error for the calculated values of pH, NH3, BOD5, COD, TDS, Cl-.
SO= 4, Na+ and Mg+2 ranges from (0.54 to 15) % which demonstrate the high predictive capacity of the models. While the high values of the determination coefficient (r higher than 0.9) for NH3,NO3, BOD5, COD, SS, Cl-. SO= 4, Na+ , Mg+2 and Oil and grease, demonstrate a good model capacity relating water values and distances downstream Finally the paper concludes that artificial purification efforts at the water works should be directed towards controlling the concentration of Cl- , SO= 4, Na+ , Ca+2 , Mg+2 which increased with increases in distance downstream and suggests further research in the area of monitoring water quality.