Acknowledgment

First, I would like to thank the Almighty God and his mother Saint Mary, who brought me to this level by making me strong and patient during hard times. Second, I would like to thank my advisor Dr. Mekibib Dawit, for his valuable advice and consistent guidance throughout the research period. This work would not have been completed in the present form without the help and cooperation of different institutions and individuals. Among others the most important ones are AAWSA, Addis Ababa EPA, J.J Labo and Ethiopian Health and Nutrition Research Institute. Valuable secondary data and field transport support was given by AAWSA. I greatly appreciate th