Post-Audit Of Alqueva Reservoir'S Water Quality: Lessons Learned With The Comparison Between Forecast And Reality

Eight years after the construction of the Alqueva dam in southern Portugal, creating the largest European artificial lake, a comparison is made between the water quality forecasts before the construction and the actual reservoir behavior. Water quality problems in the Portuguese-Spanish Guadiana basin have been a determinant issue hence one of the main discussion topics around the Alqueva project. The main goal of this study is to compare and discuss modeling results obtained before the existence of the reservoir with prototype observed data. This may contribute to learn a number of lessons. Alternative pump storage operation scenarios and reservoir filling period were some of the issues addressed before the dam was concluded, on the basis of predefined operation rules for the dam's hydraulic system and water quality monitoring data collected in the Guadiana river. Post-evaluation of simulation forecasts indicate that, if adequate assumptions are considered, reservoir modeling can indeed be used as a tool for dam project design analysis and the study of reservoir water quality issues enabling anticipatory measures towards an adequate water quality management.