In freshwater ecosystems, green algae play a key role as a microorganism's component, and the diversity of algae benefits species richness and enhances the importance of these organisms for ecosystem function. The community makeup and pollution levels in the research region can be determined using bio-diversity indices. Due to the limited information clarifying the bio-natural of the irrigation project and the extent of pollution in the study region, this study sought to give information about the planktonic green algae and evaluated them using calculated diversity indices. The study identified 54 phytoplankton green algae species collected from five sites (Mahooz village, Hawija district center, Abbasi sub-district, Zgeaton Valley, and Riyadh district), belonging to 13 families and 20 genera of Chlorophyta from October 2019 to March 2020. To measure algal diversity, four diversity indices were used: Margalef index, Shannon diversity index, Species evenness, and Simpson's diversity index. The algal community structure and pollution index at all sites were depicted using these indices. The study showed that phytoplankton communities are of higher diversity with a moderate pollution level. Phytoplankton grows and increases by responding to some environmental variables, such as nutrient availability, organic matter, and salinity caused by agricultural lands adjacent to the irrigation projects; in addition, it is impacted by the physicochemical factors of the studied region.