This book is divided into seven chapters. Each chapter deals with a particular research topic which at most parts, can be read independently. Overall, this book provides integral parts of the central theme of the study on the mechanisms of nutrient retention in a constructed wetland and what can be done to control the pollution. Chapter One provides a general introduction of nutrient retention mechanisms and the rationale of the research. Chapter Two describes the background of study sites and nutrient transport within the Cox Creek sub-catchment, South Australia. Chapter Three reported the results of flow and water quality condition and the relationship between water residence time and nutrient loadings corresponding to the flow classes. Chapter Four focuses on the nutrient storage capacity by macrophytes. Chapter Five examines the phosphorus adsorption/desorption process in wetland sediments. Chapter Six explores the role of sedimentation process to nutrient retention capacity. Finally, Chapter Seven provides a general discussion on the overall nutrient control performance of the Cox Creek constructed wetland and the implications for its maintenance.