Roadmap and Strategic Planning for Lake Dianchi Eutrophication Control
Water quality restoration efforts often suffer the risk of ineffectiveness and failure due to lack of quantitative decision supports. During the past two decades, the restoration of one of China’s most heavily polluted lakes, Lake Dianchi, has experienced costly decision ineffectiveness with no detectable water quality improvement. Without a quantitative understanding between the load reduction and the response in lake water quality, it is highly possible that the following planned efforts would suffer the similar ineffectiveness as before. To provide scientifically sound decision support for guiding future load reduction efforts in Lake Dianchi Watershed, a sophisticated quantitative cause-and-effect response system was developed using a three-dimensional modeling approach. The results show that the algal bloom in Lake Dianchi responds to load reduction in a complex and nonlinear way. Therefore, significant watershed pollutant reduction would be required even to achieve the lowest level of water quality targets (Class V), suggesting that a phased approach should be adopted to set a site-specific water quality target. Complete compliance at the highest target level (Class III) would require approximately 80% loading reduction, which seems infeasible based on available management technologies.