Estuary lakes constructed for agricultural water resources development projects have encountered eutrophication problems. Natural water purification function of wetland is considered for nutrient removal from inflowing stream. A constructed wetland was designed and installed for pollutant loading abatement in estuary lake Koheung. Combined pond-wetland system was adopted. In this system primary and secondary ponds and six wetland cells were interconnected. Reed and cattail were selected for wetland vegetation and planted in the wetland cells. In this paper, design criteria of the pond-wetland system in temperate weather zone is presented.