Physicochemical Properties of Highway Stormwater Runoff, Sulaymaniyah-Iraq

Urban stormwater runoff contributes to contamination of downstream water bodies, through washing away accumulated pollutants from streets. Studies are necessary to develop methods for managing urban runoff towards building a sustainable urban drainage system. Rainfall runoff samples were collected from Tasluja highway of Sulaymaniyah City, KRG, in fall of 2024 and tested for water quality parameters. Runoff samples were tested for temperature (T), turbidity, pH, total dissolved solids (TDS), total suspended solids (TSS), electrical conductivity (EC), zinc (Zn), cadmium (Cd), chromium (Cr), cobalt (Co), cupper (Cu), nickel (Ni), iron (Fe), lead (Pb), magnesium (Mg), and manganese (Mn) parameters. After long dry seasons, first and second rainfalls runoff samples showed significant concentrations of pollutants. Results of the study from the first flush showed the following average concentration of heavy metals in (mg/L) in descending order Mg (22.191), Fe (0.994), Mn (0.611), Zn (0.220), Cu (0.214), Ni (0.084), Cr (0.030) and Co (0.012). First rainfall test results showed higher heavy metals concentration compared to the second rainfall. Furthermore, to regulate the degree of pollution from different samples, water quality index (WQI) calculated for both rainfalls. The results demonstrated variations in stormwater WQI values ranging from 64 to 411. Results of this study suggest onsite stormwater treatment to protect nearby receiving water bodies from contamination.