ABSTRACT Water quality control is affected by several factors such as climate change or the creation of an ecological park for human convenience. The Four-River restoration project of Korea is a government enterprise to solve a variety of problems, such as preventing floods, securing water resources, water quality management, and encouraging re-creation of land. It is evidence that technical developments and the concern of the government have sharply increased for water quality management. In particular, the phenomenon of eutrophication can cause various difficulties in drinking water treatment and water use. Accurate and reliable algal bloom forecasting models will prove very useful in ensuring sustainable water supply and proper water management in the near future. In this paper, a new method based on wavelet transforms and artificial neural networks was adopted for chlorophyll-a concentration forecasting 1, 3 and 7 days ahead. First, 12 models for forecasting chlorophyll-a concentration by combining wa...