Subject of the book include ecological and taxonomical consideration for the exotic genus Potamogeton that invade Tigris River below Mosul dam after damming the river and formation of the lake. The study area cover a river stretch with about 50 km length located between Wana and Yarimja villages within Nineveh province. Book contents are divided into two parts, the first one covered the physical and chemical properties of the water, in which the hydrophytes live in, and the second one cover some taxonomical, ecological and phytochemical aspects of exotic Potamogeton genus. The present work based mainly on a Ph. D. thesis submitted to the Department of Biology, College of Sciences, University of Mosul, in 2009 by May Taha Al-Tawattar under the supervision of Dr. Basheer Ali Al-N'ima.