Egyptian Journal of Aquatic Biology & Fisheries Zoology Department, Faculty of Science, Ain Shams University, Cairo, Egypt. ISSN 1110 – 6131 Vol. 22(5): 461 - 474 (2018) www.ejabf.journals.ekb.eg Evaluation of Water Quality and Plankton for Mahmoudia Canal in Northern West of Egypt Mohamed M. M. El-Feky 1 ; Ahmed E. Alprol 1 *; Ahmed M. M. Heneash 1 ; Hamdy A. Abo-Taleb 2 and Mohsen Y. Omer 1 1- National Institute of Oceanography and Fisheries, Egypt. 2- Faculty of Science, Al-Azhar University, Egypt. * Corresponding Author: ah831992@gmail.com ARTICLE INFO ABSTRACT Article History: Received: Oct. 20, 2018 Accepted: Dec. 22, 2018 Online: Jan. 2019 _______________ Keywords: Mahmoudia canal Water quality Physical properties Phytoplankton Zooplankton Water quality describes the condition of the water, including chemical, physical, and biological characteristics, usually with regarding to its suitability for a particular purpose. The present study describes the environmental conditions of Mahmoudia canal which are the main water source for Alexandria and Behiera governorates. Water samples were collected from ten sites along the Mahmoudia canal in the year 2018 for study the seasonal variations of the water quality parameters (physicoche- mical and biological parameters). The measured physicochemical parameters include; (Turbidity, Temperature, pH, Electrical Conductivity, Total Dissolved Solids, Total Suspended Solids, Total alkalinity, Total Hardness, Nitrate, Nitrite, Ammonia, Sulfate, Phosphate, Dissolved Oxygen, Biological Oxygen Demand, Chemical Oxygen Demand, Chlorinated pesticides and some heavy metals). Phytoplankton and Zooplankton were examined as biological parameters. The values of average water quality index (WQI) of Mahmoudia canal ranged from 75.01 (poor water quality) to 132.57 (very poor water quality). According to the results of Cluster analysis, six statistically significant clusters were formed. Three groups of phytoplankton were recorded which, the annual maximum density of phytoplankton recorded in Town of Abou Hommos, while the lowest recorded in site Zawyet Ghazal Village. The highest density registered in winter (3460.2 U/ml), while the lowest density recorded in summer (831.6 U/ml). In addition to six zooplankton groups were quantified in the analysis of the samples from ten sites, the highest density listed in summer (6000 ind./m 3 ) ,although the lowest listed in winter (3200 ind./m 3 ). INTRODUCTION Water is super abundant on the planet as a whole, but fresh potable water is not always available at the right time or the right place for human or ecosystem use. Water quality refers to the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. Rivers are vital and vulnerable freshwater ecosystems that are critical for the sustenance of all life. Rivers are waterways of strategic importance across the world, providing main water resources