The wilaya of Skikda has experienced a real industrial development marked by the establishment of large factories that discharge their liquid discharges into various aquatic environments. These industrial discharges have become a factor of water pollution that may seriously threaten the stability of the environment in the few years to come.In this book we are interested in the presentation of the state of the art of aquatic environments in the North-East of Algeria by presenting particularly the physicochemical and biological qualities of the threatened watercourses.