Journal of Babylon University Vol.10 No.3-(2004) 1 Weekly and spatial variation of Physico-Chemicals variables and Algal composition in Kasnazan Impoundment, Erbil, Iraq By Janan Jabbar Toma Department of Biology, College of Science, University of Salahaddin Keyword: Weekly, Spatial variation, Algal composition, Impoundment Abstract Weekly surface water samples were taken from selected sites in Kassnazan impoundment (10Km north east of Erbil city) during 29 Oct-31 Dec 2003.Generally results showed that water temperature was ranging between 7-20C o. Average value of electrical conductivity and total dissolved solids were ranging from 350-560μs.cm -1 and 170-270mg.l -1 respectively. Water was alkaline with average alkalinity of 180-360mgCaCO 3 .pH values were on alkaline side of neutrality. The water was well aerated with dissolved oxygen value more than 7.5 mg .l -1 was recorded. The total hardness was ranged between 150-370 mgCaCO 3 .l -1 . Among the studied ions followed by calcium, magnesium, sodium and potassium. Calcium was the most abundant ions. Nitrate was the dominant inorganic from nitrogen. Phosphate and silicate showed no regular weekly variation. A total of 33 species was recorded. Chrysophyta and Chlorophyta were the dominant groups. Result showed that there is a significant increase in total number species in impoundment site was recorded. Introduction In Iraq the range of inland water types is varied. There are two major rivers, the Tigris and Euphrates and many reservoirs are found in Iraq and marshes in the south (1). Within Kurdistan part of Iraq there are a wide range of fresh water bodies in contrast to other parts of the country , fresh water areas are abundant and wide spread in Kurdistan, they take different form s Rivers, Streams, Ponds, Lakes, Impoundment, Springs....ect (2). So many studied were published on Limnological aspects of Iraqi lentic environments (3, 4,5,6and7).While Kasnazan impoundment a larger lentic system within Erbil province got less attention (8 and 9 ). So the present work would be the first attempt to characterize weekly and spatial variations of so Physico-chemicals variables in addition to algal composition in Kasnazan Impoundment. Description of the area The Erbil province (Fig.1) is capital of Kurdistan and situated in the north east of Iraq. It is bounded to the north east and south east by the Greater and Lasser Zab rivers. Boundaries extend from longitudinal 43 0 15 - E to 45 0 14 - E and from latitude 35 0 27 - N to 37 0 24 - N. The climate of the area is characterized by a wide diurnal and annual range of temperature (10). The climate most closely related to Irano-Turanian type. The average annual rainfall may exceed 1000mm.The annual average rainfall for