The researchers studied how constructed wetlands can improve water quality in a coastal reservoir. They built a wetland system in Hwaseong, South Korea, and monitored it during rainy and dry days. The wetland effectively reduced pollutants like COD, TN, and TP, with higher removal rates during rainy days. The system also decreased runoff volume during rainy days. Overall, the wetland removed over 50% of TSS, 20-35% of TP, and 26-94% of TN, showing its efficiency in cleaning the water. These findings provide important data for designing better wetlands to improve water quality in the future.